Journal articles on the topic 'Sugary exudate'
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El-Hamalawi, Zeinab A., and John A. Menge. "The Role of Snails and Ants in Transmitting the Avocado Stem Canker Pathogen, Phytophthora citricola." Journal of the American Society for Horticultural Science 121, no. 5 (September 1996): 973–77. http://dx.doi.org/10.21273/jashs.121.5.973.
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The sugary exudate appearing on bark lesions of Persea americana Miller and Persea indica plants after infection with Phytophthora citricola contained viable oospores and hyphal fragments in the field and in the greenhouse. This sugary exudate was a source of inoculum and dispersal of the pathogen within and between avocado plants. Spraying water onto lesions moved inoculum from the sugary exudate to wounds below. Water from sprinkler irrigation washed propagules into the soil around the plants. Viable propagules of Phytophthora citricola were identified in the feces of snails (Helix aspersa) that had fed on infected bark tissues. When these snails were moved to healthy plants, they made wounds on succulent tissue, and the infectious feces induced cankers. Ants (Iridomyrmex humilis) were attracted to the sugary exudate and also transmitted infectious propagules to wounds on avocado stems and to the soil. Control strategy for the avocado stem canker disease should consider control of vectors.
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Windstam, Sofia, and Eric B. Nelson. "Temporal Release of Fatty Acids and Sugars in the Spermosphere: Impacts on Enterobacter cloacae-Induced Biological Control." Applied and Environmental Microbiology 74, no. 14 (May 30, 2008): 4292–99. http://dx.doi.org/10.1128/aem.00264-08.
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ABSTRACT The aim of this study was to determine the temporal release of fatty acids and sugars from corn and cucumber seeds during the early stages of seed germination in order to establish whether sugars found in exudate can prevent exudate fatty acid degradation by Enterobacter cloacae. Both saturated (long-chain saturated fatty acids [LCSFA]) and unsaturated (long-chain unsaturated fatty acids [LCUFA]) fatty acids were detected in corn and cucumber seed exudates within 15 min after seed sowing. LCSFA and LCUFA were released at a rate of 26.1 and 6.44 ng/min/seed by corn and cucumber seeds, respectively. The unsaturated portion of the total fatty acid pool from both plant species contained primarily oleic and linoleic acids, and these fatty acids were released at a combined rate of 6.6 and 0.67 ng/min/seed from corn and cucumber, respectively. In the absence of seed exudate sugars, E. cloacae degraded linoleic acid at rates of 29 to 39 ng/min, exceeding the rate of total fatty acid release from seeds. Sugars constituted a significant percentage of corn seed exudate, accounting for 41% of the total dry seed weight. Only 5% of cucumber seed exudate was comprised of sugars. Glucose, fructose, and sucrose were the most abundant sugars present in seed exudate from both plant species. Corn seeds released a total of 137 μg/seed of these three sugars within 30 min of sowing, whereas cucumber seeds released 0.83 μg/seed within the same time frame. Levels of glucose, fructose, and sucrose found in corn seed exudate (90 to 342 μg) reduced the rate of linoleic acid degradation by E. cloacae to 7.5 to 8.8 ng/min in the presence of either sugar, leaving sufficient concentrations of linoleic acid to activate Pythium ultimum sporangia Our results demonstrate that elevated levels of sugars in the corn spermosphere can prevent the degradation of LCUFA by E. cloacae, leading to its failure to suppress P. ultimum sporangial activation, germination, and subsequent disease development.
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Padgett, Merilark, and Janice C. Morrison. "Changes in Grape Berry Exudates during Fruit Development and Their Effect on Mycelial Growth of Botrytis cinerea." Journal of the American Society for Horticultural Science 115, no. 2 (March 1990): 269–73. http://dx.doi.org/10.21273/jashs.115.2.269.
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Grape berries (Vitis vinifera L., `Thompson Seedless') exuded a variety of compounds through the cuticle and epicuticular wax layer onto the berry surface. The composition of the exudate changed through the course of the growing season. Phenolic compounds and malic acid were in relatively high concentrations in grape berry exudates after bloom, but were low in exudates from mature fruit. The rate of decrease of phenols and malic acid was more rapid during the early stage of berry growth than during the ripening period. Sugar and potassium concentrations in the berry exudates were low at bloom, but increased rapidly in the later stages of ripening. Water extracts of berry exudates contained sugars, malic acid, potassium, and sodium. The water extracts promoted mycelial growth of Botrytis cinerea Pers. Ethanol and ether extracts contained phenols and lipids. These fractions from fruit sampled in the first 3 weeks after bloom strongly inhibited mycelial growth. The inhibitory effect of these fractions decreased later in the season.
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Scher, F. M., J. W. Kloepper, and C. A. Singleton. "Chemotaxis of fluorescent Pseudomonas spp. to soybean seed exudates in vitro and in soil." Canadian Journal of Microbiology 31, no. 6 (June 1, 1985): 570–74. http://dx.doi.org/10.1139/m85-106.
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Five seed-colonizing fluorescent Pseudomonas strains (RW1 to RW5) exhibited chemotaxis toward soybean seed exudates in 1-μL capillaries held for 30 min in an 8.0 log colony-forming units/mL bacterial suspension over the temperature range of 9 to 41 °C. Dialysis (6000 molecular weight cut-off) of exudate nullified its attractiveness to RW1; heating (121 °C, 15 min) of exudate had no effect. Several amino acids present in exudate induced a chemotactic response by RW1, and asparagine, threonine, and valine at levels in exudate were as attractive as exudate. No chemotaxis by RW1 was observed toward sugars present in exudate. RW1 to RW5 actively migrated 1 cm toward soybean seeds in soil as demonstrated by a new method. A nonmotile mutant of RW3 did not migrate in soil and no significant migration by strains was observed when no seed or exudate was present. It is suggested that chemotaxis of Pseudomonas toward seed exudates may be the first step in establishment of bacterial seed and root colonization in soil.
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Kamilova, Faina, Lev V. Kravchenko, Alexander I. Shaposhnikov, Tatiyana Azarova, Nataliya Makarova, and Ben Lugtenberg. "Organic Acids, Sugars, and l-Tryptophane in Exudates of Vegetables Growing on Stonewool and Their Effects on Activities of Rhizosphere Bacteria." Molecular Plant-Microbe Interactions® 19, no. 3 (March 2006): 250–56. http://dx.doi.org/10.1094/mpmi-19-0250.
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The influence of stonewool substrate on the exudation of the major soluble carbon nutrients and of the auxin precursor tryptophane for Pseudomonas biocontrol agents was studied. To this end, the composition of the organic acids and sugars, as well that of tryptophane, of axenically collected exudates of seed, seedlings, and roots of tomato, cucumber, and sweet pepper was determined. The major results were as follows. i) The total amount of organic acid is much higher than that of total sugar. ii) Exudation of both organic acids and sugars increases during plant growth. iii) Citric, succinic, and malic acids represent the major organic acids, whereas fructose and glucose are the major sugars. iv) Compared with glass beads as a neutral substrate, stonewool substantially stimulates exudation of organic acids and sugars. v) It appeared that enhanced root-tip-colonizing bacteria isolated previously from the rhizosphere of tomato and cucumber grow much better in minimal medium with citrate as the sole carbon source than other, randomly selected rhizobacteria do. This indicates that the procedure which selects for excellent root-tip colonizers enriches for strains which utilize the major exudate carbon source citrate. vi) The content of L-tryp-tophane, the direct precursor of auxin, is approximately 60-fold higher in seedling exudates of tomato and sweet pepper than in cucumber seedling exudates, indicating a higher possibility of plant growth stimulation after inoculation with auxin-producing rhizobacteria for tomato and sweet pepper crops than for cucumber. However, the biocontrol strain Pseudomonas fluorescens WCS365, which is able to convert tryptophane into auxin, did not stimulate growth of these three crops. In contrast, this strain did stimulate growth of roots of radish, a plant which exudes nine times more tryptophane than tomato does.
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Drake, J. E., B. A. Darby, M. A. Giasson, M. A. Kramer, R. P. Phillips, and A. C. Finzi. "Stoichiometry constrains microbial response to root exudation- insights from a model and a field experiment in a temperate forest." Biogeosciences 10, no. 2 (February 7, 2013): 821–38. http://dx.doi.org/10.5194/bg-10-821-2013.
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Abstract. Plant roots release a wide range of chemicals into soils. This process, termed root exudation, is thought to increase the activity of microbes and the exoenzymes they synthesize, leading to accelerated rates of carbon (C) mineralization and nutrient cycling in rhizosphere soils relative to bulk soils. The nitrogen (N) content of microbial biomass and exoenzymes may introduce a stoichiometric constraint on the ability of microbes to effectively utilize the root exudates, particularly if the exudates are rich in C but low in N. We combined a theoretical model of microbial activity with an exudation experiment to test the hypothesis that the ability of soil microbes to utilize root exudates for the synthesis of additional biomass and exoenzymes is constrained by N availability. The field experiment simulated exudation by automatically pumping solutions of chemicals often found in root exudates ("exudate mimics") containing C alone or C in combination with N (C : N ratio of 10) through microlysimeter "root simulators" into intact forest soils in two 50-day experiments. The delivery of C-only exudate mimics increased microbial respiration but had no effect on microbial biomass or exoenzyme activities. By contrast, experimental delivery of exudate mimics containing both C and N significantly increased microbial respiration, microbial biomass, and the activity of exoenzymes that decompose low molecular weight components of soil organic matter (SOM, e.g., cellulose, amino sugars), while decreasing the activity of exoenzymes that degrade high molecular weight SOM (e.g., polyphenols, lignin). The modeling results were consistent with the experiments; simulated delivery of C-only exudates induced microbial N-limitation, which constrained the synthesis of microbial biomass and exoenzymes. Exuding N as well as C alleviated this stoichiometric constraint in the model, allowing for increased exoenzyme production, the priming of decomposition, and a net release of N from SOM (i.e., mineralization). The quantity of N released from SOM in the model simulations was, under most circumstances, in excess of the N in the exudate pulse, suggesting that the exudation of N-containing compounds can be a viable strategy for plant-N acquisition via a priming effect. The experimental and modeling results were consistent with our hypothesis that N-containing compounds in root exudates affect rhizosphere processes by providing substrates for the synthesis of N-rich microbial biomass and exoenzymes. This study suggests that exudate stoichiometry is an important and underappreciated driver of microbial activity in rhizosphere soils.
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Li, Xun, Wenying Chu, Jinlong Dong, and Zengqiang Duan. "An Improved High-performance Liquid Chromatographic Method for the Determination of Soluble Sugars in Root Exudates of Greenhouse Cucumber Grown under CO2 Enrichment." Journal of the American Society for Horticultural Science 139, no. 4 (July 2014): 356–63. http://dx.doi.org/10.21273/jashs.139.4.356.
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This study described a simple and quick method to detect trace quantities of a non-reducing sugar (viz. sucrose) in the root exudates of cucumber (Cucumis sativus) under CO2 enrichment. Sucrose was determined by analyzing fructose and glucose before and after invertase digestion using high-performance liquid chromatography. Using this technique, the optimal hydrolysis condition was 5.00 μg·mL−1 invertase for 10 minutes. The detection limit of ultraviolet-visible detector by post-column derivatization with tetrazolium was 0.25, 0.43, 0.48, and 1.95 μg·mL−1 for fructose, glucose, sucrose, and maltose, respectively, and sensitive enough for determination of sugars in root exudates. The dry weight of cucumber at the seedling stage (19 days after transplant) increased by 58.4% when the CO2 level was elevated from 380 to 1200 μmol·mol−1, whereas the differences were not significant at the initial fruiting stage (63 days after transplant). The photosynthesis rate in 1200 μmol·mol−1 CO2 was 58.0% higher than that in 380 μmol·mol−1 CO2 at the seedling stage and 74.2% higher at the initial fruiting stage. Total amount of sugars in cucumber root exudates was significantly increased with increasing CO2 concentration. The total sugars in root exudates increased by 130.4% and 102.3% in 1200 μmol·mol−1 CO2 compared with that in 380 μmol·mol−1 CO2 at seedling and initial fruiting stages, respectively. Elevated CO2 altered sugar composition in root exudates. Sugars in root exudates released per plant were significantly higher at the initial fruiting stage than that at the seedling stage, whereas the differences in sugars released per gram of root tissue between these two growth stages were not significant. Our results suggest that sugars were increased only in as much as root mass increased. This study provides a simple and quick method to detect 1 to 500 μg·mL−1 sugars in root exudates, and the results illustrate the variation in the sugar composition in cucumber root exudates among the CO2 levels and growth stages.
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Lothier, Jérémy, Houssein Diab, Caroline Cukier, Anis M. Limami, and Guillaume Tcherkez. "Metabolic Responses to Waterlogging Differ between Roots and Shoots and Reflect Phloem Transport Alteration in Medicago truncatula." Plants 9, no. 10 (October 15, 2020): 1373. http://dx.doi.org/10.3390/plants9101373.
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Root oxygen deficiency that is induced by flooding (waterlogging) is a common situation in many agricultural areas, causing considerable loss in yield and productivity. Physiological and metabolic acclimation to hypoxia has mostly been studied on roots or whole seedlings under full submergence. The metabolic difference between shoots and roots during waterlogging, and how roots and shoots communicate in such a situation is much less known. In particular, the metabolic acclimation in shoots and how this, in turn, impacts on roots metabolism is not well documented. Here, we monitored changes in the metabolome of roots and shoots of barrel clover (Medicago truncatula), growth, and gas-exchange, and analyzed phloem sap exudate composition. Roots exhibited a typical response to hypoxia, such as γ-aminobutyrate and alanine accumulation, as well as a strong decline in raffinose, sucrose, hexoses, and pentoses. Leaves exhibited a strong increase in starch, sugars, sugar derivatives, and phenolics (tyrosine, tryptophan, phenylalanine, benzoate, ferulate), suggesting an inhibition of sugar export and their alternative utilization by aromatic compounds production via pentose phosphates and phosphoenolpyruvate. Accordingly, there was an enrichment in sugars and a decline in organic acids in phloem sap exudates under waterlogging. Mass-balance calculations further suggest an increased imbalance between loading by shoots and unloading by roots under waterlogging. Taken as a whole, our results are consistent with the inhibition of sugar import by waterlogged roots, leading to an increase in phloem sugar pool, which, in turn, exert negative feedback on sugar metabolism and utilization in shoots.
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Han, Sanghyun, and Shirley A. Micallef. "Environmental Metabolomics of the Tomato Plant Surface Provides Insights on Salmonella enterica Colonization." Applied and Environmental Microbiology 82, no. 10 (March 18, 2016): 3131–42. http://dx.doi.org/10.1128/aem.00435-16.
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ABSTRACTFoodborne illness-causing enteric bacteria are able to colonize plant surfaces without causing infection. We lack an understanding of how epiphytic persistence of enteric bacteria occurs on plants, possibly as an adaptive transit strategy to maximize chances of reentering herbivorous hosts. We used tomato (Solanum lycopersicum) cultivars that have exhibited differential susceptibilities toSalmonella entericacolonization to investigate the influence of plant surface compounds and exudates on enteric bacterial populations. Tomato fruit, shoot, and root exudates collected at different developmental stages supported growth ofS. entericato various degrees in a cultivar- and plant organ-dependent manner.S. entericagrowth in fruit exudates of various cultivars correlated with epiphytic growth data (R2= 0.504;P= 0.006), providing evidence that plant surface compounds drive bacterial colonization success. Chemical profiling of tomato surface compounds with gas chromatography-time of flight mass spectrometry (GC-TOF-MS) provided valuable information about the metabolic environment on fruit, shoot, and root surfaces. Hierarchical cluster analysis of the data revealed quantitative differences in phytocompounds among cultivars and changes over a developmental course and by plant organ (P< 0.002). Sugars, sugar alcohols, and organic acids were associated with increasedS. entericagrowth, while fatty acids, including palmitic and oleic acids, were negatively correlated. We demonstrate that the plant surface metabolite landscape has a significant impact onS. entericagrowth and colonization efficiency. This environmental metabolomics approach provides an avenue to understand interactions between human pathogens and plants that could lead to strategies to identify or breed crop cultivars for microbiologically safer produce.IMPORTANCEIn recent years, fresh produce has emerged as a leading food vehicle for enteric pathogens.Salmonella-contaminated tomatoes represent a recurrent human pathogen-plant commodity pair. We demonstrate thatSalmonellacan utilize tomato surface compounds and exudates for growth. Surface metabolite profiling revealed that the types and amounts of compounds released to the plant surface differ by cultivar, plant developmental stage, and plant organ. Differences in exudate profiles explain some of the variability inSalmonellacolonization susceptibility seen among tomato cultivars. Certain medium- and long-chain fatty acids were associated with restrictedSalmonellagrowth, while sugars, sugar alcohols, and organic acids correlated with largerSalmonellapopulations. These findings uncover the possibility of selecting crop varieties based on characteristics that impair foodborne pathogen growth for enhanced safety of fresh produce.
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Dutra, Carmelo, María Verónica Cesio, Patrick Moyna, and Horacio Heinzen. "Acyl Sucroses from Salpichroa Origanifolia." Natural Product Communications 3, no. 4 (April 2008): 1934578X0800300. http://dx.doi.org/10.1177/1934578x0800300413.
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The exudate of Salpichroa origanifolia (Solanaceae) foliar glandular trichomes has been characterized chemically. It was demonstrated to be a complex mixture of hexaesters of short chain fatty acids and sucrose. Of the total exudates, 80% was 1′,6′-diacetyl-2,3,4,6-tetra(3-methyl valerianyl)-sucrose, a new natural product, which showed antifungal properties against Aspergillus niger. It is the first report of sugar esters in the genus Salpichroa.
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Bayliss, Catherine, Elizabeth Bent, Doreen E. Culham, Shawn MacLellan, Anthony J. Clarke, Janet M. Wood, and Gerry L. Brown. "Bacterial genetic loci implicated in thePseudomonas putidaGR12-2R3 – canola mutualism: identification of an exudate-inducible sugar transporter." Canadian Journal of Microbiology 43, no. 9 (September 1, 1997): 809–18. http://dx.doi.org/10.1139/m97-118.
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Pseudomonas putida GR12-2R3 promotes the emergence and growth of diverse plant species. Analyses of TnphoA insertion mutations are revealing bacterial characteristics pertinent to the plant–microbe interaction. Pseudomonas putida PG269 is a TnphoA insertion derivative of GR12-2R3 that expresses canola seed exudate-inducible alkaline phosphatase (PhoA) activity. It promoted the growth of canola roots, as well as strain GR12-2R3, and outgrew its parent when they were cocultured in the presence of canola roots or in liquid seed exudate medium. (In contrast, mutant PG126 failed to promote canola root growth and was outgrown by its parent strain.) The PhoA activity of strain PG269 was induced by glucosamine and other sugars; glucosamine inhibited the growth of strain GR12-2R3 and stimulated the growth of strain PG269. Strain PG269 contained two TnphoA insertions: seiA1:: TnphoA and seiB1:: TnphoA. Strain PG312, which contained only insertion seiA1:: TnphoA, shared all aspects of the PG269 phenotype, except the ability to outcompete strain GR12-2R3 during coculture. Insertion seiA1::TnphoA interrupted an open reading frame related in sequence to members of the MalF family of sugar transporter subunits. The PhoA-inducing fraction of canola seed exudate was hydrophilic, low in molecular weight, and heat stable. It cochromatographed with basic amino acids and amino sugars, and was inactivated by strains GR12-2R3 and PG269. Gene seiA may encode a subunit of an ABC transporter with broad specificity for glucose and related sugars whose expression can be induced by exudate sugars.Key words: Pseudomonas putida, canola, exudate, sugar transport, rhizobacterium.
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Fourie, J. F., and G. Holz. "Effects of Fruit and Pollen Exudates on Growth of Botrytis cinerea and Infection of Plum and Nectarine Fruit." Plant Disease 82, no. 2 (February 1998): 165–70. http://dx.doi.org/10.1094/pdis.1998.82.2.165.
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Sugars in exudates from Harry Pickstone plum and Sunlite nectarine fruit and from pollen of weeds commonly found in orchards were determined by gas-liquid chromatography, and their effect on the development of Botrytis cinerea was determined in vitro and in vivo. Fructose, glucose, and sorbitol were the only sugars detected in exudates of immature fruit. They occurred at low concentrations, but their concentration generally increased as fruit ripened. Sucrose was first detected during maturation. In nectarine, an increase in sugar concentration, especially sucrose, was pronounced during the period of rapid cell enlargement, which occurred approximately 2 weeks before harvest. Absorbance readings of culture media amended with sugar indicated that the hexose sugars (fructose and glucose) and sucrose did not markedly influence growth of B. cinerea at concentrations below 0.22 and 0.12 mM, respectively. The hexose sugars caused a steady increase in growth when supplied at concentrations in excess of 0.44 mM, and sucrose caused a steady increase in growth at 0.23 mM. The stimulatory effect of fruit exudates on growth of B. cinerea on glass slides coincided with the period of rapid sugar release from the fruit and the shift in susceptibility to decay. Only fructose (1.72 mM) and glucose (0.72 mM) were detected in nectarine pollen exudates. Pollen exudates from weeds stimulated fungal growth and significantly increased the aggressiveness of the pathogen on plum and nectarine fruit when added to conidia during the last 4 weeks prior to the picking-ripe stage. The study showed that changes in the composition of nectarine and plum fruit exudates may contribute to the late-season susceptibility of these fruit to B. cinerea infection.
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Krishnapriya, Vengavasi, and Renu Pandey. "Root exudation index: screening organic acid exudation and phosphorus acquisition efficiency in soybean genotypes." Crop and Pasture Science 67, no. 10 (2016): 1096. http://dx.doi.org/10.1071/cp15329.
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High-molecular-weight secretory proteins and low-molecular-weight exudates (carboxylates, phenols, free amino acids and sugars) released from roots of soybean (Glycine max (L.) Merr.) differentially influence genotypic phosphorus (P) acquisition efficiency (PAE). We hypothesised that genotypes with higher root exudation potential would exhibit enhanced P acquisition, and screened 116 diverse soybean genotypes by labelling shoots with 14CO2. A root exudation index (REI) derived from total 14C in the root exudate at sufficient (250 μm) and low (4 μm) P levels was used to classify genotypes for PAE. Genotypes with REI >2.25 exhibited significantly higher exudation at low than at sufficient P, which in turn increased PAE. Under low P availability, efficient genotypes exude a greater quantity of organic compounds into the rhizosphere. This increases P availability to meet the crop requirement, enabling the crop to produce consistent biomass and seed yield with reduced fertiliser addition. Such maintenance of growth and yield potential by mining the inherent soil P is a favourable trait in genotypes, reducing dependence on P fertilisers. Measuring REI at seedling stage to select P-efficient plants accelerates the screening process by accommodating large numbers of genotypes.
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Amiard, Véronique, Annette Morvan-Bertrand, Jean-Bernard Cliquet, Jean-Pierre Billard, Claude Huault, Jonas P. Sandström, and Marie-Pascale Prud'homme. "Carbohydrate and amino acid composition in phloem sap of Lolium perenne L. before and after defoliation." Canadian Journal of Botany 82, no. 11 (November 1, 2004): 1594–601. http://dx.doi.org/10.1139/b04-117.
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Carbohydrate and amino acid composition of phloem sap was studied in the grass Lolium perenne L., before and after defoliation. Leaf exudate was collected in a 5 mmol·L1 EDTA solution from cut leaf blades or stubble, and phloem sap was obtained through excised aphid (Rhopalosiphum padi L.) stylets. Results indicate that leaf exudates obtained from leaves devoid of petiole might not be relevant predictors of carbohydrate content of pure phloem sap. Sucrose was the dominating carbohydrate, accounting for 93% of the total soluble sugars in the phloem sap. Myo-inositol, glucose, and fructose were present in trace amounts, while fructans, raffinose, and loliose have never been detected. Predominant amino acid in the phloem sap was glutamine followed by glutamate, aspartate, and serine. Phloem sap component concentration declined during the first hours following defoliation. Sucrose was the main sugar transported in the phloem sap of Lolium perenne, despite the fact that the product of fructan degradation was fructose and not sucrose. The results are discussed in relation with the physiological mechanisms that contribute to plant recovery after defoliation.Key words: fructan, sucrose, loliose, defoliation, phloem sap, amino acids.
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de Weert, Sandra, Hans Vermeiren, Ine H. M. Mulders, Irene Kuiper, Nico Hendrickx, Guido V. Bloemberg, Jos Vanderleyden, René De Mot, and Ben J. J. Lugtenberg. "Flagella-Driven Chemotaxis Towards Exudate Components Is an Important Trait for Tomato Root Colonization by Pseudomonas fluorescens." Molecular Plant-Microbe Interactions® 15, no. 11 (November 2002): 1173–80. http://dx.doi.org/10.1094/mpmi.2002.15.11.1173.
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Motility is a major trait for competitive tomato root-tip colonization by Pseudomonas fluorescens. To test the hypothesis that this role of motility is based on chemotaxis toward exudate components, cheA mutants that were defective in flagella-driven chemotaxis but retained motility were constructed in four P. fluorescens strains. After inoculation of seedlings with a 1:1 mixture of wild-type and nonmotile mutants all mutants had a strongly reduced competitive root colonizing ability after 7 days of plant growth, both in a gnotobiotic sand system as well as in non-sterile potting soil. The differences were significant on all root parts and increased from root base to root tip. Significant differences at the root tip could already be detected after 2 to 3 days. These experiments show that chemotaxis is an important competitive colonization trait. The best competitive root-tip colonizer, strain WCS365, was tested for chemotaxis toward tomato root exudate and its major identified components. A chemotactic response was detected toward root exudate, some organic acids, and some amino acids from this exudate but not toward its sugars. Comparison of the minimal concentrations required for a chemotactic response with concentrations estimated for exudates suggested that malic acid and citric acid are among major chemo-attractants for P. fluorescens WCS365 cells in the tomato rhizosphere.
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Drake, J. E., B. A. Darby, M. A. Giasson, M. A. Kramer, R. P. Phillips, and A. C. Finzi. "Stoichiometry constrains microbial response to root exudation – insights from a model and a field experiment in a temperate forest." Biogeosciences Discussions 9, no. 6 (June 13, 2012): 6899–945. http://dx.doi.org/10.5194/bgd-9-6899-2012.
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Abstract. Healthy plant roots release a wide range of chemicals into soils. This process, termed root exudation, is thought to increase the activity of microbes and the exo-enzymes they synthesize, leading to accelerated rates of carbon (C) mineralization and nutrient cycling in rhizosphere soils relative to bulk soils. The causal role of exudation, however, is difficult to isolate with in-situ observations, given the complex nature of the rhizosphere environment. We investigated the potential effects of root exudation on microbial and exo-enzyme activity using a theoretical model of decomposition and a field experiment, with a specific focus on the stoichiometric constraint of nitrogen (N) availability. The field experiment isolated the effect of exudation by pumping solutions of exudate mimics through microlysimeter "root simulators" into intact forest soils over two 50-day periods. Using a combined model-experiment approach, we tested two hypotheses: (1) exudation alone is sufficient to stimulate microbial and exo-enzyme activity in rhizosphere soils, and (2) microbial response to C-exudates (carbohydrates and organic acids) is constrained by N-limitation. Experimental delivery of exudate mimics containing C and N significantly increased microbial respiration, microbial biomass, and the activity of exo-enzymes that decompose labile components of soil organic matter (SOM, e.g., cellulose, amino sugars), while decreasing the activity of exo-enzymes that degrade recalcitrant SOM (e.g., polyphenols, lignin). However, delivery of C-only exudates had no effect on microbial biomass or overall exo-enzyme activity, and only increased microbial respiration. The theoretical decomposition model produced complementary results; the modeled microbial response to C-only exudates was constrained by limited N supply to support the synthesis of N-rich microbial biomass and exo-enzymes, while exuding C and N together elicited an increase in modeled microbial biomass, exo-enzyme activity, and decomposition. Thus, hypothesis (2) was supported, while hypothesis (1) was only supported when C and N compounds were exuded together. This study supports a cause-and-effect relationship between root exudation and enhanced microbial activity, and suggests that exudate stoichiometry is an important and underappreciated driver of microbial activity in rhizosphere soils.
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Ayaz, F. A., A. Kadioglu, and R. Turgut. "Water stress effects on the content of low molecular weight carbohydrates and phenolic acids in Ctenanthe setosa (Rosc.) Eichler." Canadian Journal of Plant Science 80, no. 2 (April 1, 2000): 373–78. http://dx.doi.org/10.4141/p99-005.
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Morphological and biochemical changes in plant cells are known as important events for adaptation to stress. In this study, changes in carbohydrate and phenolic acid concentrations during leaf rolling under water stress were investigated. Leaves of vegetatively propagated Ctenanthe setosa (Rosc.) Eichler plants started to roll after a 28-d water deficit. After approximately 33–35 d, the leaves were tightly rolled. Water stress significantly increased the dry weight of rolled leaves. Low molecular dry weight carbohydrate components identified in unrolled and rolled leaves were fructose, glucose, inositol and sucrose. Leaves of stressed plants tended to accumulate more carbohydrates of low molecular weight. The same sugars (except inositol) were also identified in liquid and crystal forms of exudates, which appeared on the abaxial surface of the leaves during leaf rolling. The phenolic acids identified in unrolled and rolled leaves were from the benzoic group (benzoic, salicylic, 4-hydroxybenzoic, vanillic, 3,4-dihydroxybenzoic, syringic acids), and the cinnamic group (ferulic and caffeic acids both in free and methyl ester form and cis- and trans-p-coumaric acids). All phenolic acid concentrations (except for salicylic acid) in the phenolic group increased in rolled leaves in comparison with unrolled leaves. In the cinnamic group, the amounts of cis- and trans-p-coumaric and caffeic acids were greater in rolled leaves than in unrolled leaves. Key words: Ctenanthe setosa, exudate, crystal, leaf rolling, sugar, phenolic acid
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Coutinho, Ítalo Antônio Cotta, Vânia Maria Moreira Valente, and Renata Maria Strozi Alves Meira. "Ontogenetic, anatomical and histochemical study of the extrafloral nectaries of Sapium biglandulosum (Euphorbiaceae)." Australian Journal of Botany 58, no. 3 (2010): 224. http://dx.doi.org/10.1071/bt09200.
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The present paper aims to confirm the nature of secretory structures found on the petiole and leaf margins of Sapium biglandulosum Müell. Arg. The anatomy, ontogenesis and histochemistry were studied by light microscopy, whereas mono- and disaccharides in the exudates were detected by high performance liquid chromatography. The exudate from the petiole had a total sugar concentration of 32.5% (w/v), of which 38.1% was fructose, 43.7% glucose and 18.2% sucrose. The petiolar gland started its development from a group of meristematic cells that underwent asynchronous divisions. At the end of the ontogenesis, a well structured vascularised gland made up of a palisade secretory epidermis, secretory parenchyma and a secretory pore was observed. Leaf-margin glands showed a similar anatomy. Histochemical tests revealed the presence of proteins, pectins, carbohydrates, tannins and anthocyanins. On the basis of our results, there is compelling evidence that the studied glands are in fact extrafloral nectaries.
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Lombardo, Fabien, Pietro Gramazio, and Hiroshi Ezura. "Increase in Phloem Area in the Tomato hawaiian skirt Mutant Is Associated with Enhanced Sugar Transport." Genes 12, no. 6 (June 18, 2021): 932. http://dx.doi.org/10.3390/genes12060932.
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The HAWAIIAN SKIRT (HWS) gene has been described in Arabidopsis, rice, tomato and poplar where it seems to perform distinct functions with relatively little overlap. In tomato, alteration of the gene function confers facultative parthenocarpy, thought to be a consequence of changes in the microRNA metabolism. In the rice mutant, improvement in panicle architecture is associated with an increase in grain yield. Knowing that hws tomato fruits show a higher Brix level, it was suspected that vascular bundles might also be altered in this species, in a similar fashion to the rice phenotype. The pedicel structure of the hws-1 line was therefore examined under the microscope and sugar concentrations from phloem exudate were determined in an enzymatic assay. A distinct increase in the phloem area was observed as well as a higher sugar content in mutant phloem exudates, which is hypothesized to contribute to the high Brix level in the mutant fruits. Furthermore, the described phenotype in this study bridges the gap between Arabidopsis and rice phenotypes, suggesting that the modulation of the microRNA metabolism by HWS influences traits of agricultural interest across several species.
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Rocha, Diego Ismael, Luzimar Campos da Silva, Vânia Maria Moreira Valente, Dayana Maria Teodoro Francino, and Renata Maria Strozi Alves Meira. "Morphoanatomy and development of leaf secretory structures in Passiflora amethystina Mikan (Passifloraceae)." Australian Journal of Botany 57, no. 7 (2009): 619. http://dx.doi.org/10.1071/bt09158.
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Extrafloral nectaries (EFNs) are commonly found in Passiflora L. Reports have been made on the occurrence of resin-producing structures morphologically similar to EFNs in the genus. The objective of this study was to characterise the morphoanatomy and development of leaf secretory structures in Passiflora amethystina and to use chemical and histochemical tests to detect the presence of sugars in the exudates. Samples of leaf blade and petioles in different developmental stages were collected and subjected to usual techniques using light and scanning electron microscopy. Secretion samples were analysed by high performance liquid chromatography. The concentration of total sugars in the secretion amounted to 39.67% for blade EFNs and 52.82% for petiolar EFNs. EFNs consist of a secretory, uni- or bistratified palisade epidermis, arising from the protoderm by means of anticlinal and periclinal divisions, glandular parenchyma originated from the ground meristem, and xylem and phloem elements formed from the procambium. Exudate accumulated in a subcuticular space formed outside the epidermal cells from where it was then released. Histochemical tests showed a positive reaction for neutral polysaccharides. The results confirm that the leaf secretory structures are indeed extrafloral nectaries, and these findings constitute important information for studies on the taxonomy and ecology of this species.
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Lee, Keuk-Ki, Robert C. Shearman, and Robert V. Klucas. "Nitrogen fixation (acetylene reduction) by lines composing 'Park' Kentucky bluegrass." Canadian Journal of Microbiology 32, no. 4 (April 1, 1986): 348–52. http://dx.doi.org/10.1139/m86-067.
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Response of 'Park' Kentucky bluegrass to inoculation with Klebsiella pneumoniae strain W-6 was tested under field conditions. Field inoculation did not increase nitrogenase activity measured in situ, but did increase the nitrogenase activity as measured using an excised root assay which included a 10-h incubation before the addition of acetylene. Fifteen lines composing 'Park' were grown in fritted-clay medium, inoculated with soil, and compared for nitrogenase activities using the excised roots assay. Significant differences were observed between two lines. Six lines were selected from the 15 lines, grown hydroponically, inoculated with soil, and assayed for nitrogenase activity using intact 105-day-old plants. Nitrogenase activities were immediately detectable and increased curvilinearly. Differences in nitrogenase activities among the six lines were detected within 1 h and significant differences were evident in 4 h. The six selected lines were also tested for levels of anthrone-reactive sugars in roots and root exudates of hydroponically grown plants. Significant differences were detected in levels of sugars in roots but not in root exudates. Possible correlations were sought among and within the three different experiments involving the six selected lines. With hydroponically grown plants, nitrogenase activities during the first 4 h were highly correlated with those after 24 h incubation. Correlations were found between nitrogenase activities in excised roots and soluble sugar concentrations in root tissue and root exudates.
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Kuiper, Irene, Lev V. Kravchenko, Guido V. Bloemberg, and Ben J. J. Lugtenberg. "Pseudomonas putida Strain PCL1444, Selected for Efficient Root Colonization and Naphthalene Degradation, Effectively Utilizes Root Exudate Components." Molecular Plant-Microbe Interactions® 15, no. 7 (July 2002): 734–41. http://dx.doi.org/10.1094/mpmi.2002.15.7.734.
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Previously, we have described the selection of a plant-bacterium pair that is efficient in rhizoremediating naphthalene pollution in microcosm studies. After repeated selection for efficient root tip colonization upon inoculation of seeds of grass cv. Barmultra and for stable and efficient growth on naphthalene, Pseudomonas putida PCL1444 was selected as the most efficient colonizer of Barmultra roots. Here, we report the analysis of Barmultra root exudate composition and our subsequent tests of the growth rate of the bacterium and of the expression of the naphthalene degradation genes on individual exudate components. High performance liquid chromatography analysis of the organic acid and sugar root-exudate components revealed that glucose and fructose are the most abundant sugars, whereas succinic acid and citric acid are the most abundant organic acids. Tn5luxAB mutants of PCL1444 impaired in naphthalene degradation appeared to be impaired in genes homologous to genes of the upper naphthalene degradation pathway present in various Pseudomonas strains and to genes of the lower pathway genes for naphthalene degradation in P. stutzeri. Highest expression for both pathways involved in naphthalene degradation during growth in minimal medium with the carbon source to be tested was observed at the start of the logarithmic phase. Naphthalene did not induce the upper pathway, but a different pattern of expression was observed in the lower pathway reporter, probably due to the conversion of naphthalene to salicylic acid. Salicylic acid, which is described as an intermediate of the naphthalene degradation pathway in many Pseudomonas strains, did induce both pathways, resulting in an up to sixfold higher expression level at the start of the logarithmic phase. When expression levels during growth on the different carbon sources present in root exudate were compared, highest expression was observed on the two major root exudate components, glucose and succinic acid. These results show an excellent correlation between successful naphthalene rhizoremediation by the Barmultra-P. putida PCL1444 pair and both efficient utilization of the major exudate components for growth and high transcription of the naphthalene catabolic genes on the major exudate components. Therefore, we hypothesize that efficient root colonizing and naphthalene degradation is the result of the applied colonization enrichment procedure.
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Trusty, Susan E., and William B. Miller. "CHARACTERIZATION OF TRANSLOCATED CARBOHYDRATES AND DIURNAL CHANGES IN CHRYSANTHEMUM LEAVES." HortScience 25, no. 9 (September 1990): 1076H—1077. http://dx.doi.org/10.21273/hortsci.25.9.1076.
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Exudation of phloem sap into EDTA (ethylenediaminetetraacetic acid) solutions has been found to be a successful technique for qualitatively determining translocated assimilates in many plants. Mature Chysanthemum leaves were excised under a solution of 10 mM EDTA (pH 7.0). The petioles of these leaves were placed in EDTA, and leaf exudate was collected at intervals for 24 h. Soluble carbohydrates were determined with HPLC. While numerous sugars were present in the leaf, sucrose was the only sugar found in the EDTA solutions. The greatest rate of sucrose exudation occurred in the first two h after excision. Diurnal fluctuations of soluble sugars in Chrysanthemum leaves were also monitored in greenhouse-grown plants (late winter in Arizona). Sucrose exhibited a clear diurnal fluctuation, and nearly doubled in concentration (to appx. 25 mg/g DWT) in the afternoon relative to the low in the morning. Other leaf carbohydrates, including glucose, starch, and fructans showed diurnal variations as well.
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Trusty, Susan E., and William B. Miller. "CHARACTERIZATION OF TRANSLOCATED CARBOHYDRATES AND DIURNAL CHANGES IN CHRYSANTHEMUM LEAVES." HortScience 25, no. 9 (September 1990): 1076h—1077. http://dx.doi.org/10.21273/hortsci.25.9.1076h.
Full textAbstract:
Exudation of phloem sap into EDTA (ethylenediaminetetraacetic acid) solutions has been found to be a successful technique for qualitatively determining translocated assimilates in many plants. Mature Chysanthemum leaves were excised under a solution of 10 mM EDTA (pH 7.0). The petioles of these leaves were placed in EDTA, and leaf exudate was collected at intervals for 24 h. Soluble carbohydrates were determined with HPLC. While numerous sugars were present in the leaf, sucrose was the only sugar found in the EDTA solutions. The greatest rate of sucrose exudation occurred in the first two h after excision. Diurnal fluctuations of soluble sugars in Chrysanthemum leaves were also monitored in greenhouse-grown plants (late winter in Arizona). Sucrose exhibited a clear diurnal fluctuation, and nearly doubled in concentration (to appx. 25 mg/g DWT) in the afternoon relative to the low in the morning. Other leaf carbohydrates, including glucose, starch, and fructans showed diurnal variations as well.
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Koch, Birgit, Tommy H. Nielsen, Dan Sørensen, Jens Bo Andersen, Carsten Christophersen, Søren Molin, Michael Givskov, Jan Sørensen, and Ole Nybroe. "Lipopeptide Production in Pseudomonas sp. Strain DSS73 Is Regulated by Components of Sugar Beet Seed Exudate via the Gac Two-Component Regulatory System." Applied and Environmental Microbiology 68, no. 9 (September 2002): 4509–16. http://dx.doi.org/10.1128/aem.68.9.4509-4516.2002.
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ABSTRACT Pseudomonas sp. strain DSS73 isolated from the sugar beet rhizosphere produces the cyclic lipopeptide amphisin, which inhibits the growth of plant-pathogenic fungi. By Tn5::luxAB mutagenesis, we obtained two nonproducing mutant strains, DSS73-15C2 and DSS73-12H8. The gene interrupted by the transposon in strain DSS73-15C2 (amsY) encoded a protein with homology to peptide synthetases that was designated amphisin synthetase. DSS73-12H8 carried the transposon in a regulatory gene encoding a protein with homology to the sensor kinase GacS. Growth of strain DSS73-15C2 (amsY) was impaired during the transition to stationary phase in a minimal medium amended with an exudate of sugar beet seeds. This growth phenotype could be complemented by purified amphisin. Seed exudate further induced expression of bioluminescence from the amsY::luxAB reporter during the transition to stationary phase. This agreed with an increase in amphisin production by the DSS73 wild-type strain during early stationary phase. Amphisin synthesis in DSS73 was strictly dependent on GacS, and even induction by seed exudate depended on a functional gacS locus. Hence, a signal triggering the GacS/GacA two-component system appeared to be present in the seed exudate.
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Klages, Karin, Helen Donnison, Helen Boldingh, and Elspeth MacRae. "myo-Inositol is the major sugar in Actinidia arguta during early fruit development." Functional Plant Biology 25, no. 1 (1998): 61. http://dx.doi.org/10.1071/pp97052.
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Actinidia arguta (Sieb. et Zucc.) Planch. ex Miq. is a cold tolerant and heavy cropping species from the kiwifruit [Actinidia deliciosa var. deliciosa (A. Chev.) C.F. Liang et A.R.Ferguson] family that has potential for commercialisation. As fruit developed, glucose was the major sugar (74%) in A. deliciosa during the first 40 days after anthesis, whereas myo-inositol was the major sugar (60–65%) in A. arguta.myo-Inositol accumulated rapidly in A. arguta during the first 20–30 daa then more slowly as fruit grew to reach a steady state level, between 15 and 50 mg fruit-1 for different selections. Peak levels were 55-60 mg g-1 dry wt. In contrast, maximum myo-inositol concentrations in A. deliciosa were only 18 mg g-1 dry wt. As fruit of A. arguta ripened, sucrose became the dominant sugar. In contrast to the fruit, myo-inositol concentrations were lower in leaves of A. arguta(~5 mg g-1 dry wt; ~10% of major sugars) than in leaves of A. deliciosa (15 mg g-1 dry wt; ~20% of major sugars). To ascertain whether myo-inositol was transported from the leaves to the fruit in the phloem stream, exudates were also analysed. In both species, sucrose was the predominant sugar (>95%) in the phloem. Therefore we suggest that an unusual accumulation of myo-inositol in A. arguta during early stages of fruit development, may be due to synthesis in the fruit.
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Hou, Chen, Richard M. K. Saunders, Nan Deng, Tao Wan, and Yingjuan Su. "Pollination Drop Proteome and Reproductive Organ Transcriptome Comparison in Gnetum Reveals Entomophilous Adaptation." Genes 10, no. 10 (October 12, 2019): 800. http://dx.doi.org/10.3390/genes10100800.
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Gnetum possesses morphologically bisexual but functionally unisexual reproductive structures that exude sugary pollination drops to attract insects. Previous studies have revealed that the arborescent species (G. gnemon L.) and the lianoid species (G. luofuense C.Y.Cheng) possess different pollination syndromes. This study compared the proteome in the pollination drops of these two species using label-free quantitative techniques. The transcriptomes of fertile reproductive units (FRUs) and sterile reproductive units (SRUs) for each species were furthermore compared using Illumina Hiseq sequencing, and integrated proteomic and transcriptomic analyses were subsequently performed. Our results show that the differentially expressed proteins between FRUs and SRUs were involved in carbohydrate metabolism, the biosynthesis of amino acids and ovule defense. In addition, the differentially expressed genes between the FRUs and SRUs (e.g., MADS-box genes) were engaged in reproductive development and the formation of pollination drops. The integrated protein-transcript analyses revealed that FRUs and their exudates were relatively conservative while the SRUs and their exudates were more diverse, probably functioning as pollinator attractants. The evolution of reproductive organs appears to be synchronized with changes in the pollination drop proteome of Gnetum, suggesting that insect-pollinated adaptations are not restricted to angiosperms but also occur in gymnosperms.
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Davis, R. M., and J. E. Fucik. "Effect of Girdling Sour Orange Seedlings on Mycorrhizal Development." HortScience 21, no. 2 (April 1986): 302–4. http://dx.doi.org/10.21273/hortsci.21.2.302.
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Abstract Six-month-old nonmycorrhizal or mycorrhizal [Glomus fasciculatum (Thaxter) Gerd. and Trappe] sour orange (Citrus aurantium L.) seedlings grown in a sandy soil amended with 0, 50, or 100 μg P/g soil were completely girdled 5 mm below the basal leaves. Eight weeks later, root exudates and extracts were analyzed and one-half of the nonmycorrhizal plants were inoculated with G. fasciculatum. Amounts of soluble sugars were greater in exudates from girdled nonmycorrhizal plants than in exudates from nongirdled or mycorrhizal plants. Girdling consistently reduced the amount of sugars in root extracts in all plants. Amounts of amino acids in exudates or extracts were not consistently affected by any treatment. Intensity of mycorrhizal infection was similar in girdled and nongirdled plants grown in sand without supplemental phosphorus, but mycorrhizal development was insignificant in plants inoculated after girdling and grown in sand amended with 50 or 100 μg P/g soil. Root infection was apparently dependent both on levels of photosynthates supplied to the roots and on the amount of nutrients in root exudates.
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Kim, Tae Yeon, Jeong-Yong Cho, Yu Geon Lee, Hang Yeon Jeong, Hyoung Jae Lee, and Jae-Hak Moon. "Phenolics and eudesmanolide from aged common sage exudate with sugar." Food Science and Biotechnology 26, no. 6 (December 2017): 1491–500. http://dx.doi.org/10.1007/s10068-017-0234-8.
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Lawrence Pusey, P., David R. Rudell, Eric A. Curry, and James P. Mattheis. "Characterization of Stigma Exudates in Aqueous Extracts from Apple and Pear Flowers." HortScience 43, no. 5 (August 2008): 1471–78. http://dx.doi.org/10.21273/hortsci.43.5.1471.
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The stigmatic secretions of pomaceous flowers serve as a natural medium not only for pollen, but also for the pathogen Erwinia amylovora (Burr.) Winslow et al. and other microorganisms. To understand the microecology on the stigma, exudates from cultivars of pear (Pyrus communis L.), apple (Malus pumila P. Mill.), and crab apple [Malus mandshurica (Maxim.) Kom.] were analyzed for free sugars and free amino acids as available carbon and nitrogen sources. Extracts were obtained at different stages of anthesis by submerging and sonicating stigmas in water. Certain free sugars (glucose and fructose) and free amino acids (proline, asparagine, glutamic acid, and glutamine) were consistently predominant and increased during anthesis. Apple stigma extracts were also analyzed for polysaccharides and proteins. Of major components identified for apple, free sugars made up 4.5% by mass; polysaccharides (composed of arabinose and galactose), 49.6%; and proteins, 45.9%. The two largest components are likely present as glycoproteins. This may be the first report on characteristics of rosaceous stigma exudates that includes the identity of specific free sugars, free amino acids, and polysaccharide subcomponents. Discussion includes the comparison of pomaceous stigma exudates to those of other plants and the microecological implications.
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Wood, Bruce W. "Carbohydrate Composition of Vascular System Exudates and Characterization of Their Uptake by Leaf Tissue of Pecan." Journal of the American Society for Horticultural Science 112, no. 2 (March 1987): 346–51. http://dx.doi.org/10.21273/jashs.112.2.346.
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Abstract In an effort to identify the primary transfer carbohydrates and to describe their characteristics of uptake by pecan [Carya illinoensis (Wangenh C. Koch)] leaf disks, it was discovered that the major carbohydrates in pecan xylem and phloem exudate and leaf free space leachate were sucrose, fructose, glucose, and inositol. Sucrose was the primary component of each of these systems. Uptake of sucrose, glucose, and fructose by leaf tissues was biphasic with a saturable active (sensitive to CCCP) carrier-like component and a nonsaturating passive (insensitive to CCCP) diffusion-like component. Uptake by the saturable component predominated at levels below 8 and 14 mM for fructose and glucose, respectively, and up to at least 40 mM for sucrose. The observations of a preponderance of sucrose in the free space of leaf disk and a sucrose Vmax an order of magnitude greater than for fructose or glucose suggests that sucrose is the major uptake carbohydrate moving from the leaf free space into the cytoplasm. The observation that uptake of any of these three sugars was noncompetitively inhibited by the other two sugars and that their uptake was unequally influenced by metabolic inhibitors suggests the possible presence of a separate carrier for each sugar. Sucrose uptake also appeared to be without hydrolysis and was coupled to the co-transport of protons with uptake diminishing with decreasing apoplastic proton levels.
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Arora, Dilip K., and Sushma Gupta. "Effect of different environmental conditions on bacterial chemotaxis toward fungal spores." Canadian Journal of Microbiology 39, no. 10 (October 1, 1993): 922–31. http://dx.doi.org/10.1139/m93-140.
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The chemotactic response of four common soil bacteria, Agrobacterium radiobacter, Bacillus subtilis, Pseudomonas fluorescens, and Xanthomonas malvacearum, was observed in natural soil to conidia of Cochliobolus sativus, chlamydospores of Fusarium oxysporum f.sp. ciceri, sclerotia of Macrophomina phaseolina, and oospores of Phytophthora drechsleri f.sp. cajani. All bacteria migrated through soil toward fungal spores. Chemical analysis of fungal exudates demonstrated the presence of various amino acids and sugars that served as chemoattractants. The effect of temperature, pH, soil water matric potential, and soil texture on bacterial chemotaxis toward fungal spores was also investigated. In general, the response of bacteria to different types of fungal spores was significantly greater (P = 0.05) at higher water matric potential (0 and −5 kPa) than at lower soil water potential (−10 and −20 kPa). The chemotactic response was greatest in sandy soil, followed by sandy loam and clay loam soil. High temperature (40 °C) was not favourable for bacterial chemotaxis. The chemotactic response decreased by 4 to 28 times when soil pH decreased from 7 to 5 or increased from 7 to 9. The relative concentration response of the exudate of fungal spores and the motility or chemotaxis of bacteria were assessed. A significant positive correlation (P = 0.05; r = 0.89–0.92) was recorded between motility and relative concentrations of exudate. The swimming speed and tumbling frequency of Pseudomonas fluorescens cells was observed at different pH values and temperatures. The swimming speed of bacteria increased with increasing temperature, but decreased with an increase in pH from 5 to 7. The tumbling frequency had a sharp peak at 30 °C and pH 7. Bacteria were able to stimulate the release of exudate from the fungal spores. The amount of exudation was also affected by temperature, pH, and soil texture. A positive significant correlation (P = 0.05; r = 0.79–0.85) was recorded between exudation and a progressive increase in temperature. The amount of exudation also increased with an increase in soil pH from 5 to 8, but further increases in pH decreased the rate of exudation. In general, fungal spores exuded the greatest amounts of carbon compounds in sandy soil, followed by sandy loam and clay loam soil. Exudation in sandy soil was often greatest in the presence of A. radiobacter cells, while the greatest exudation in sandy loam and clay loam soils was induced by B. subtilis cells.Key words: chemotaxis, chemoattractants, fungal spores, motility.
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Goffreda, J. C., J. C. Steffens, and M. A. Mutschler. "Association of Epicuticular Sugars with Aphid Resistance in Hybrids with Wild Tomato." Journal of the American Society for Horticultural Science 115, no. 1 (January 1990): 161–65. http://dx.doi.org/10.21273/jashs.115.1.161.
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Behavioral studies have shown that aphid resistance in Lycopersicon pennellii (Corr.) D'Arcy is due to the presence of sugar esters in glandular exudate of the type IV trichomes. In this study, various methods for the estimation of epicuticular sugar ester concentrations were examined. There was a significant negative relationship between the concentration of sugar esters on the leaf and the level of potato aphid infestation in a segregating L. esculentum × L. pannellii F2 population. Selection for sugar ester accumulation should be an efficient selection technique for the aphid resistance of L. pennellii and other species that synthesize epicuticular sugar esters.
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Saavedra-Sanabria, Olga L., Daniel Durán, Jessica Cabezas, Inés Hernández, Cristian Blanco-Tirado, and Marianny Y. Combariza. "Cellulose biosynthesis using simple sugars available in residual cacao mucilage exudate." Carbohydrate Polymers 274 (November 2021): 118645. http://dx.doi.org/10.1016/j.carbpol.2021.118645.
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Nikolova, Milena, Ana Dobreva, and Strahil Berkov. "Wastes after distillation of Helichrysum italicum – biological active compounds and free radical scavenging activity." Acta Biologica Szegediensis 64, no. 2 (April 10, 2021): 233–37. http://dx.doi.org/10.14232/abs.2020.2.233-237.
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Distillation wastewater, by-products from steam and water distillation as well as raw material used as control of flower heads of Helichrysum italicum were comparative analyzed for content of the biologically active compounds by GC/MS. Acetone exudates, methanol extracts and ethyl acetate fractions obtained after alkaline hydrolyze of the studied materials were received. The three types of extraction products as well as the distillation wastewater were examined for free radical scavenging activity by DPPH assay. Phenol, fatty- and organic acids, sterols, triterpenes, sugars and sugar alcohols were identified. Succinic acid and myo-inositol were identified as main components of distillation wastewater. Hydroxycinnamic acid, caffeic acid and 4(p)-hydroxybenzoic acid were dominant compounds of the ethyl acetate fractions. Triterpenes and fatty acids, sterols and flavonoids are among the main biologically active substances in the methanolic extracts and acetone exudates. The ethyl acetate fractions were found to possess the highest free radical scavenging activity (IC50 < 50 µg/mL). Significant differences in the activity between wastes and raw materials were not found. The results showed that the waste products after distillation of H. italicum contain important biologically active substances and the extracts with high antioxidant activity can be obtained from them.
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Dundek, Peter, Ladislav Holík, Tomáš Rohlík, Ladislav Hromádko, Valerie Vranová, Klement Rejšek, and Pavel Formánek. "Methods of plant root exudates analysis: a review." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 59, no. 3 (2011): 241–46. http://dx.doi.org/10.11118/actaun201159030241.
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The aim of this review is to summarise current knowledge on methods being used to determine individual compounds and properties of water-soluble plant root exudates. These compounds include amino acids, organic acids and simple sugars, as well as polysaccharides, proteins and organic substances. Qualitative composition of water-soluble root exudates and exudation rate are commonly measured with the aim of consequent synthetic preparation of plant root exudates to be supplied to soil to create artificial rhizosphere for different experimental purposes. Root exudates collection usually requires consequent filtration or centrifugation to remove solids, root detritus and microbial cell debris, and consequent concentration using an evaporator, lyophilizator or ultrafiltration. Methods used for analysis of total groups of compounds (total proteins and total carbohydrates) and total organic carbon are simple. On the other hand, HPLC or GS/MS are commonly used to analyse individual low molecular weight organic molecules (sugars, organic acids and amino acids) with separation using different columns. Other properties such as pH, conductivity or activity of different enzymes as well as gel electrophoresis of proteins are sometimes assessed. All of these methods are discussed in this work.
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Kobayashi, Akio, Myong Jo Kim, and Kazuyoshi Kawazu. "Uptake and Exudation of Phenolic Compounds by Wheat and Antimicrobial Components of the Root Exudate." Zeitschrift für Naturforschung C 51, no. 7-8 (August 1, 1996): 527–33. http://dx.doi.org/10.1515/znc-1996-7-811.
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Abstract In the course of our study, it was found that phenyl propenoic acid derivatives were readily taken up by wheat. Leaf leachate components were chosen for the feeding experiments and p-coumaric acid, ferulic acid and caffeic acid were found to be quickly taken up into the plants via the roots. The analytical study revealed that the exudate contained potent antimicrobial compounds together with amino acids and sugars. Besides the primary metabolites, 4-hydroxystyrene, 3-methoxy-4-hydroxystyrene and 3-methoxy-4-acetoxystyrene were identified as exudate components from wheat roots in sterile hydroponic culture. This indicates that these antimicrobial components may play a significant role in the defense system as allelochemicals for the rhizosphere.
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Vranová, Valerie, Hana Kaňová, Klement Rejšek, and Pavel Formánek. "Dominant amino acids, organic acids and sugars in water-soluble root exudates of C4 plants: a mini-review." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 58, no. 5 (2010): 441–46. http://dx.doi.org/10.11118/actaun201058050441.
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The aim of this mini-review was to identify the dominant carbohydrates, organic acids and amino acids in water-soluble root exudates of plants which represent dominant compounds there. The study is focused on plants of C4-type of metabolism taking into account available literature. From group of carbohydrates, those dominant are represented glucose, fructose, arabinose and sucrose. Between dominant amino acids occurring in root exudates of C4-metabolism plants are alanine, serine, arginine, glutamine, glutamic and aspartic acid, glycine, proline, cystine, lysine and g-aminobutyric acid. Citric, malic, tartaric, succinic, trans-aconitic represent the dominant organic acids. This knowledge may be useful for planning analyses of these compounds in root exudates of C4plants. Except for this preparation of synthetic root exudates to simulate rhizosphere of C4plants may be performed based on these results.
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Forney, Charles F., and Patrick J. Breen. "Collection and Characterization of Phloem Exudate from Strawberry Pedicels." HortScience 20, no. 3 (June 1985): 413–14. http://dx.doi.org/10.21273/hortsci.20.3.413.
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Abstract Fruit of strawberry (Fragaria ×ananassa Duch. ‘Brighton’) were removed, and pedicels attached to plants were placed in ethylenediaminetetraacetate (EDTA) to collect phloem sap. The rate of sugar exudation increased with the size of the fruit, but was lower than the rate of dry matter accumulation of the fruit at the time of its removal. When plants were fed 14CO2, radioactivity appeared in the phloem sap after 3 hr, and the rate of exudation of labeled assimilate was maintained at a fairly constant rate for 6 hr. About 92% of the radioactivity in the exudate was in the sucrose fraction, with the remaining in glucose (2%), fructose (1%), and acidic and basic fractions (4%). The results indicate that sucrose is the major assimilate translocated to the fruit.
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Wu, Jiong, Changdi Ke, Yanqun Zu, Yu Din, and Taiting Li. "Root morphological, Cd accumulation and tolerance characteristics of 2 Dianthus caryophyllus cultivars under Cd stress." E3S Web of Conferences 271 (2021): 04012. http://dx.doi.org/10.1051/e3sconf/202127104012.
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For studying the physiological response of two different Dianthus caryophyllus cultivars on Cd stress, pot experiment was carried out to measure proline and glutathione in leaves, five types of organic acids in root exudates (oxalic acid, malic acid, acetic acid, tartaric acid, citric acid), soluble sugars and free amino acids, root length, root surface area, root volume, root projected area and Cadmium content in soil, plant roots and aboveground. According to the effects of cadmium stress on the physiological and biochemical characteristics of two Dianthus caryophyllus, the results showed that: the growth of two cultivars are affected, “Master” and “Xiao Yan” are manifested as plant height, leaf, flower buds and biomass decreased, but the “Master” by the stronger inhibitory effect. The root length, total root surface area, total root projected area, and average root diameter of the “Master” increased under cadmium stress, but the root volume decreased. However, the root length, total root surface area, root volume, and root projected area of the “Xiao Yan” under cadmium stress decreased, while the average root diameter increased. The glutathione in the leaves of the two cultivars decreased, the proline content of the leaves of the “Xiao Yan” increased, while that of the “Master” decreased. In the root exudates, the free amino acid content of the two cultivars are reduced, and the secretion of organic acids is also inhibited (except for the citric acid secreted in the “Master”), while the soluble sugar content in the root exudates is expressed as “Xiao Yan” increased, and the “Master” decreased. According to the physiological response to the two cultivars under cadmium stress, the “Xiao Yan” is more suitable for soil restoration in the mining area of Lanping area.
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Tauwhare, Stephen E. K., Roger H. Newman, Suzanne Scheele, and Rangi TE Kanawa. "Chemotaxonomy ofPhormiumbased on sugar‐residue analyses of the leaf exudates." New Zealand Journal of Botany 44, no. 2 (January 2006): 129–33. http://dx.doi.org/10.1080/0028825x.2006.9513013.
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Kaňová, Hana, Joffrey Carre, Valerie Vranová, Klement Rejšek, and Pavel Formánek. "Organic compounds in root exudates of Miscanthus × Giganteus greef et deu and limitation of microorganisms in its rhizosphere by nutrients." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 58, no. 5 (2010): 203–8. http://dx.doi.org/10.11118/actaun201058050203.
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This study was conducted to determine the composition of sugars and organic acids in root exudates of Miscanthus × Giganteus and to find out if microorganisms of the rhizospheric soil are limited by mineral nutrients. The following sugars and organic acids were determined in root exudates of this plant: glucose, saccharose, and acids such as succinic, propionic, citric, tartaric, malic, oxalic, ascorbic, acetic and fumaric. Respiration of soil from rhizosphere of Miscanthus × Giganteus was found to be limited by N, K and Ca. Respiration rate after application of mineral compounds increased in following orther: nitrate > calcium > potassium > ammonium, giving approx. 165, 99, 52 and 31 % increase compared to control. Further research is necessary to determine the role of plant nutrients from the point of their limitations for rhizosphere microorganisms, to broader very rare knowledges in this topic, especially for polluted soils to stimulate efficiency of phytoremediations.
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Lu, Peina, Tony Yang, Lijun Li, Baoping Zhao, and Jinghui Liu. "Response of oat morphologies, root exudates, and rhizosphere fungal communities to amendments in a saline-alkaline environment." PLOS ONE 15, no. 12 (December 3, 2020): e0243301. http://dx.doi.org/10.1371/journal.pone.0243301.
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The application of organic amendments to saline-alkaline soil has been recommended as an agricultural strategy to improve crop productivity and soil health. However, there has been limited research on how organic soil amendment strategies affect the health of oats and their associated rhizosphere fungal communities in saline-alkaline conditions. Thus, the objectives of this study were to understand the effects of oat cultivars with contrasting saline-alkaline tolerances and different amendments on plant morphologies, root exudates (soluble sugars and organic acids), and rhizosphere fungal communities in a saline-alkaline environment. Experiments were conducted on a saline-alkaline tolerant cultivar, Baiyan2, and a saline-alkaline sensitive cultivar, Caoyou1, under four different organic amendment strategies: 1. control (no amendment application), 2. bio-fertilizer application, 3. rotten straw application, and 4. a co-application of bio-fertilizer and rotten straw. Results showed that plant morphological characters of Baiyan2 were better than Caoyou1, and that soluble sugar and organic acid levels in the rhizosphere of Baiyan2 were significantly lower than Caoyou1. Compared to the control, oat root and plant development was significantly improved by the combined bio-fertilizer and rotten straw amendment. Bio-fertilizer application promoted malic and citric acid levels, contributing to a higher total organic acid level, and significantly increased the abundance of Rhizopus arrhizus and decreased the abundance of the fungal pathogens Alternaria, Cladosporium, Sarocladium and Heydenia of Ascomycota in both oat cultivars. All amendment treatments containing rotten straw, except the combined amendment in Baiyan2, significantly increased the relative abundance of Ascomycota (specifically Gibberella, Talaromyces, Fusarium, and Bipolaris) and decreased the relative abundance of R. arrhizus by reducing soluble sugar and organic acid levels. For the combined amendment in Baiyan2, there were no significant changes in Gibberella and Rhizopus between the control and amendment treatment. Our results suggest that co-application of bio-fertilizer and rotten straw, combined with a tolerant oat cultivar, is an effective method to increase crop productivity and enhance soil health in a saline-alkaline environment.
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Kanaujia, R. S. "Studies on ceratain aspects of root surface fungi. I Fungi on living roots of Pennisetum typhoides (Burm f.) Stapf et Hubb." Acta Mycologica 17, no. 1-2 (August 20, 2014): 5–25. http://dx.doi.org/10.5586/am.1981.001.
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The present paper deals with the succession of fungi on the root regions of living <i>Pennisetum typhoides</i>. The presence and amounts of amino acids and sugars in root exudates (July to October) and root extracts (July to November) have been studied.
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Wang, Zhen Hong, Hong Fang, and Mouhui Chen. "Effects of root exudates of woody species on the soil anti-erodibility in the rhizosphere in a karst region, China." PeerJ 5 (March 1, 2017): e3029. http://dx.doi.org/10.7717/peerj.3029.
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IntroductionRhizospheres, the most active interfaces between plants and soils, play a central role in the long-term maintenance of the biosphere. The anti-erodibility of soils (AES) regulated by the root exudates is crucial to the soil stability in the rhizospheres. However, scientists still debate (1) the key organic matter of the root exudates affecting the AES and (2) the interspecific variation of these root exudates.MethodsWe used an incubation of soils to test the effects of the root exudates from eight woody plant species on the change in soil aggregation and identified the organic matter in these root exudates with gas chromatography-mass spectrometry (GC-MS) and biochemical methods. Furthermore, the relationships between the organic matter in the exudates and the AES in the rhizospheres of 34 additional tree species were analyzed.ResultsThe water-stable aggregates of the soils incubated with the root exudates increased by 15%–50% on average compared with control samples. The interspecific differences were significant. The root exudates included hundreds of specific organic matter types; hydrocarbon, total sugar, total amino acids, and phenolic compounds were crucial to the AES. These organic matter types could explain approximately 20–75% of the variation in the total effect of the root exudates on the AES, which was quantified based on the aggregate status, degree of aggregation, dispersion ratio, and dispersion coefficient.DiscussionThe effects of the root exudates on the AES and the interspecific variation are as important as that of root density, litters, and vegetation covers. Many studies explored the effects of root density, litters, vegetation covers, and vegetation types on the AES, but little attention has been paid to the effects of the root exudates on the AES. Different plants secrete different relative contents of organic matter resulting in the variation of the effect of the root exudates on the AES. Our study quantified the causal relationships between the root exudates and the AES using modeling experiments in laboratory and field observations and indicated the interspecific variation of the AES and organic matter of the root exudates.ConclusionsMore organic compounds of the exudates related to the AES were recognized in this study. These results enhance the understanding of the soil stability at a slope and can be applied to ecosystem restoration.
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Knee, Emma M., Fang-Chen Gong, Mensheng Gao, Max Teplitski, Angela R. Jones, Angel Foxworthy, Andrew J. Mort, and Wolfgang D. Bauer. "Root Mucilage from Pea and Its Utilization by Rhizosphere Bacteria as a Sole Carbon Source." Molecular Plant-Microbe Interactions® 14, no. 6 (June 2001): 775–84. http://dx.doi.org/10.1094/mpmi.2001.14.6.775.
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Plant roots secrete a complex polysaccharide mucilage that may provide a significant source of carbon for microbes that colonize the rhizosphere. High molecular weight mucilage was separated by high-pressure liquid chromatography gel filtration from low molecular weight components of pea root exudate. Purified pea root mucilage generally was similar in sugar and glycosidic linkage composition to mucilage from cowpea, wheat, rice, and maize, but appeared to contain an unusually high amount of material that was similar to arabinogalactan protein. Purified pea mucilage was used as the sole carbon source for growth of several pea rhizosphere bacteria, including Rhizobium leguminosarum 8401 and 4292, Burkholderia cepacia AMMD, and Pseudomonas fluorescens PRA25. These species grew on mucilage to cell densities of three- to 25-fold higher than controls with no added carbon source, with cell densities of 1 to 15% of those obtained on an equal weight of glucose. Micromolar concentrations of nod gene-inducing flavonoids specifically stimulated mucilage-dependent growth of R. leguminosarum 8401 to levels almost equaling the glucose controls. R. leguminosarum 8401 was able to hydrolyze p-nitrophenyl glycosides of various sugars and partially utilize a number of purified plant polysaccharides as sole carbon sources, indicating that R. leguminosarum 8401 can make an unexpected variety of carbohydrases, in accordance with its ability to extensively utilize pea root mucilage.
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Pereira, Lucas Caiubi, Carolina Bertuzzi Pereira, Larissa Vinis Correia, Thaisa Cavalieri Matera, Rayssa Fernanda dos Santos, Cristiane de Carvalho, Elisete Aparecida Fernandes Osipi, and Alessandro Lucca Braccini. "Corn Responsiveness to Azospirillum: Accessing the Effect of Root Exudates on the Bacterial Growth and Its Ability to Fix Nitrogen." Plants 9, no. 7 (July 21, 2020): 923. http://dx.doi.org/10.3390/plants9070923.
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Corn has shown different degrees of positive response to inoculation with the nitrogen- fixing bacteria of the genera Azospirillum. Part of it has been attributed to the plant genotypic variation, including the root exudates, that are used by the bacteria as energy source. In this study, we grew two corn hybrids that differ for their response to Azospirillum, to investigate the effect of different exudates profiles on the bacteria growth and nitrogenase activity. Employing high performance liquid chromatography, we identified nine amino acids (asparagine, aspartic acid, serine, glutamic acid, valine, phenylalanine, threonine, tryptophan and alanine), six sugars (glucose, sucrose, xylose, arabinose, fructose and galactose) and four organic acids (citrate, malate, succinate and fumarate). The less responsive corn genotype showed reduced plant growth (root volume, shoot dry mass and shoot N content), a lower concentration of Azospirillum cells within the root tissues, a higher content of asparagine and glucose and a reduced amount of metabolites that serve as bacterial energy source (all organic acids + five sugars, excluding glucose). The genotypes did not interfere in the ability of Azospirillum to colonize the substrate, but the metabolites released by the less responsive one reduced the nitrogenase activity.
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Chetverikov, Sergey, Lidiya Vysotskaya, Elena Kuzina, Tatiana Arkhipova, Margarita Bakaeva, Gulnaz Rafikova, Tatiana Korshunova, Darya Chetverikova, Gaisar Hkudaygulov, and Guzel Kudoyarova. "Effects of Association of Barley Plants with Hydrocarbon-Degrading Bacteria on the Content of Soluble Organic Compounds in Clean and Oil-Contaminated Sand." Plants 10, no. 5 (May 13, 2021): 975. http://dx.doi.org/10.3390/plants10050975.
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Plant-bacteria consortia are more effective in bioremediation of petroleum contaminated soil than when either organism is used individually. The reason for this is that plant root exudates promote growth and activity of oil degrading bacteria. However, insufficient attention has been paid to the ability of bacteria to influence root exudation. Therefore, the influence of barley plants and/or bacterial inoculation (Pseudomonas hunanensis IB C7 and Enterobacter sp. UOM 3) on the content of organic acids, sugars and plant hormones in the eluate from clean and oil-polluted sand was studied separately or in combination. These strains are capable of oxidizing hydrocarbons and synthesizing auxins. Concentrations of organic acids and sugars were determined using capillary electrophoresis, and hormones by enzyme-linked immunosorbent assays. In the absence of plants, no sugars were detected in the sand, confirming that root exudates are their main source. Introducing bacteria into the sand increased total contents of organic compounds both in the presence and absence of oil. This increase could be related to the increase in auxin amounts in the sand eluate, as well as in plants. The results indicate that bacteria are able to increase the level of root exudation. Since auxins can promote root exudation, bacterial production of this hormone is likely responsible for increased concentrations of soluble organic compounds in the sand. Bacterial mediation of root exudation by affecting plant hormonal status should be considered when choosing microorganisms for phytoremediation.
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Zheng, Huifang, Miaomiao Cai, Yucong Bai, Junlei Xu, Yali Xie, Huajian Song, Juan Li, and Jian Gao. "The Effect of Guttation on the Growth of Bamboo Shoots." Forests 13, no. 1 (December 28, 2021): 31. http://dx.doi.org/10.3390/f13010031.
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Guttation is the process of exudating droplets from the tips, edges, and adaxial and abaxial surfaces of the undamaged leaves. Guttation is a natural and spontaneous biological phenomenon that occurs in a wide variety of plants. Despite its generally positive effect on plant growth, many aspects of this cryptic process are unknown. In this study, the guttation phenomenon characteristic of bamboo shoots and the anatomical feature of these and culm sheaths were systematically observed. In addition, the water transport pathway and the compounds in guttation droplets of bamboo shoots were analyzed, and the effect of bamboo sheaths’ guttation on the growth of bamboo shoots was assessed. The results revealed that bamboo shoots began to exudate liquid in the evening through to the next morning, during which period the volume of guttation liquid gradually increases and then decreases before sunrise. Many vascular bundles are in bamboo shoots and culm sheaths to facilitate this water transport. The exudate liquid contains organic acids, sugars, and hormones, among other compounds. Our findings suggest that the regular guttation of the sheath blade is crucial to maintain the normal growth of bamboo shoots.
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Klages, Karin, Helen Donnison, Jens Wünsche, and Helen Boldingh. "Diurnal changes in non-structural carbohydrates in leaves, phloem exudate and fruit in ‘Braeburn’ apple." Functional Plant Biology 28, no. 2 (2001): 131. http://dx.doi.org/10.1071/pp00077.
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Diurnal changes in carbohydrates in leaves, phloem exudate and within fruitwere determined in apple trees grown under high, low or no crop load. Inleaves, diurnal patterns of carbohydrate concentrations were most distinct inhigh-cropping trees and least so in non-cropping trees. In phloem exudate,sorbitol comprised about 65–70% of sugars and sucrose30–35%, with clear diurnal patterns in the amounts. Phloemexudates from stalks of sun and shade fruit were similar. Fruit carbohydratesshowed little diurnal variation. Crude fruit extracts showed little differencein sucrose synthase (SS, EC 2.4.1.13) activity between crop loads, whilesucrose phosphate synthase (SPS, EC 2.4.1.14) activity in high-cropping treespeaked at night and in low-cropping trees in the morning. SPS activity inshade fruit from high-cropping trees was only half of that in sun fruit (atmidday). Results indicate that the greater weight of individual fruit from lowcrop loads is primarily due to greater supply from the source, rather thanhigher metabolic activity in the sink, compared to fruit from high crop loads.In contrast, fruit size differences in sun and shade fruit of high-croppingtrees appear to be due to differences in sink metabolism rather than supplyfrom the source.