Dissertations / Theses on the topic 'Plant growth'

Recent preliminary data have suggested that microbe-to-plant signals, and plant internal signals elicited by microbial signals, affect aspects of plant physiology, development and growth. The reported research investigated the responses of plants to signal compounds of microbial and plant origin, such as lipo-chitooligosaccharides (LCOs - signal molecules in rhizobia-legume associations), chitin and chitosan (present in fungal cell walls), and phenolic compounds (salicylic acid, acetylsalicylic acid and gentisic acid - internal signals in plants, often affected by signals from microbes). Phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) are key enzymes of the phenylpropanoid pathway. Oligomers of chitin and chitosan increased the activities of both PAL and TAL in soybean leaves. The degree of increase was dependent on oligomer chain length and time after treatment. LCO [Nod Bj V (C18:1 , MeFuc)] was isolated from Bradyrhizobium japonicum strain 532C. When Arabidopsis thaliana plants were grown for two weeks on agar containing this LCO (10-8M) or chitin pentamer (10-4 M), they had greater root length, root diameter, root surface area and number of root tips than control plants. Chitosan (tetramer and pentamer) did not have this effect. Chitin and chitosan were also tested for effects on corn and soybean photosynthetic rates and growth. High molecular weight chitosan generally reduced photosynthetic rates, but did not reduce the growth of corn or soybean. However, foliar application of 10-6 M LCO to corn leaves increased photosynthetic rates (up to 36%). Foliar application of lumichrome (10-5 and 10-6 M), a breakdown product of riboflavin produced by some rhizosphere bacteria, to corn (C4 plant) and soybean (C3 plant) increased photosynthetic rates (up to 6%). Foliar application of lumichrome (10-5 M) increased soybean leaf area and shoot dry weight. Foliar application of SA, acetyl salicylic acid (ASA) and gentisic acid (GT

Thesis (M.S. in Management)--Naval Postgraduate School, June 1990.
Thesis Advisor(s): Carrick, Pual M. "June 1990." Description based on signature page. DTIC Identifier(s): Plant growth regulators, growth indicators. Author(s) subject terms: Plant growth regulators, growth indicators. Includes bibliographical references (p. 39-40). Also available online.

Salad tomatoes represent an important vegetable crop within Australia. However, the costs of both materials and labour involved in providing this crop with artificial support, in the form of trellising or staking, is high. This project examined the feasibility of using the plant growth regulator, paclobutrazol, as an aid to crop grown without trellising or staking under coastal conditions. Initially a rate of 4 mg plant-, applied as a soil drench 1, 15, 29, 47 or 57 days after transplanting were compared with non-treated plants under glasshouse conditions. The application of paclobutrazol 1 day after transplanting (DAT), and to a lesser extent 15 DAT. profoundly changed growth while later applications (29, 47 or 57 DAT) had little effect. This sensitivity of young tomato plants to paclobutrazol was confirmed in a field trial where 5 rates (nil, 6.25, 12.50, 25.00 and 50.00 g a.i. ha-1) were applied at one of three application times (12, 40 or 60 DAT). Paclobutrazol only effected growth and physiology. when applied at the earliest time while later applications did not appreciably effect salad tomatoes regardless of rate. It was postulated that salad tomatoes remain sensitive to paclobutrazol up to the event of floral initiation. When applied early the highest rate tested produced the most profound changes and there was no evidence of residual effects on a gucceeding lettuce crop. though later applications did cause a slight stimulatory effect to lettuce dry matter accumulation. It was concluded that paclobutrazol was unlikely to cause residual effects to succeeding crops when applied to tomatoes during their sensitive stage and at rates within those tested. A further field experiment tested in more detail the effects of this compound on growth and some aspects of physiology. Paclobutrazol was found to inhibit several important plant characters, viz: height, leaf and stem dry matter accumulation and leaf areas. Conversely it stimulated the partitioning of assimilate to leaves, specific leaf weights, net photosynthesis on a leaf basis, net assimilation rate and water use efficiency on a gas exchange basis. However the stimulatory and inhibitory effects appear to cancel each other out such that treated and untreated plants had similar crop growth rates and fruit yields. Hence, these studies do not present evidence suggesting that this compound has a role to play as an aid to unsupported semi-determinate salad tomato crops, as no yield benefit was conferred.

Responses of rice to plant growth regulators on germination and seedling growth under NaCl salinity were studied to identify possible means of increasing salinity tolerance. Gibberellic acid (GA) promoted germination processes and a-amylase activity and increased plumule but reduced radicle growth after emergence. GA partitioned more metabolites towards the plumule than the radicle. Chlormequat (CCC) showed no beneficial effects and abscisic acid (ABA) inhibited germination under saline conditions. Overall there was no large difference in the performance of three rice varieties, BR29, IR8 and Pokkali in germination. Artificially aged seeds showed increased sensitivity to salinity and GA produced similar effects on germination of artificially aged rice seeds as on unaged seeds. Seed pre-treatment with GA was as effective in promoting germination under saline conditions as applying GA in the germination media. GA with low Ca promoted germination and plumule growth as well as radicle growth. GA increased plant height and fresh weight of seedlings under saline conditions, however it did not show a large positive effect on rice seedlings. CCC had no beneficial effects on rice seedlings. ABA showed possible beneficial effects on rice seedlings as it reduced Na+ uptake and increased K+ and Ca2+ uptake. GA in combination with ABA appeared to adapt rice plants better to saline conditions. GA in combination with low Ca also promoted rice growth under saline conditions.

A knowledge of the allometry of algal growth and respiration can be applied to biomass-size distribution models which are in turn used in the prediction of fish yield and ecosystem studies. However, the scaling exponents reported in the literature are variable. This variation may be attributed to differences in the expression of cell size and phylogeny, but could also reflect small sample size which underlie most published regressions. This thesis establishes the allometry of algal growth and respiration based on a larger sample taken from the literature, and evaluates the effects of differences in gross taxonomy and in the expression of cell size on these relations. Allometric relations based on cell carbon appear more consistent with relations from other taxa than those based on cell volume, reflecting the size dependence of algal elemental composition which does not occur in most other taxa. The allometric relation of algal respiration (R in pl O$ rm sb2 cdot cell sp{-1} cdot hr sp{-1})$ was found to be R = 0.030C$ sp{0.93}$ where C is cell carbon content in pg C$ rm cdot cell sp{-1}$. Among the 6 divisions studied (Chlorophyta, Chrysophyta, Cyanophyta, Euglenophyta, Pyrrophyta, Rhodophyta), chlorophytes, euglenophytes and rhodophytes exhibited different respiration-size relation but separate relations were not developed for each of those groups due to patterns in residuals or small sample sizes. The specific rate of algal growth ($ mu$ in divisions$ cdot$day$ sp{-1}$) also depends on size and it is found to be $ mu$ = 3.45C$ sp{-0.21}.$ All taxa studied here (Chlorophyta, Chrysophyta, Pyrrophyta) have similar scaling exponents for growth but Pyrrophyta have significantly lower growth rates than other algae of similar size.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (page 47).
A novel design of extendable robotic arm inspired by plant growth is presented. The robot can construct its own body structure by converting a type of fluidized material into a rigid structure at its growing point. It extends its structure in multiple directions, and move through a winding space to reach a point, which is otherwise difficult to access. The robot with the rigid structure can also bear a more significant load than existing growing robot, has a plate to attach an end-effector, and can transport an object. The robot satisfies three key functional requirements that are characteristic to plant growth. First, the robot is capable of transporting structural materials to its growing point. Second, the robot is capable of transforming the material into a rigid structure. Third, it is capable of steering its growing point so that it extends in a desired direction. A proof-of-concept prototype is then presented that consists of a customized chain that can be switched between fluidized and rigid states, a winch that can transport the chain, and a steering system to direct the growing direction. The prototype meets all the functional requirements by moving along a path and retract to the starting position. What follows this prototype is the second design that solves some issues found in the first design. Details of major changes from the initial design are presented and is validated in a virtual environment.
by Tongxi Yan.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering

Physiologic responses to Gibberellic Acid (GA), I-Naphthalene Acetic Acid (NAA), Benzylaminopurine (BAP), and Abscisic Acid (ABA). suggest that Oosterium monilfferum has the ability to utilize these plant growth factors. The growth promoters NAA and GA both increased growth when added to the media. The cell division regulator BAP (a synthetic cytokinin). also had a promotive effect on growth. Abscisic acid was found to be inhibitive to growth.

Abandoned agricultural lands in the Intermountain West are plagued by dense, persistent non-native vegetation. Targeted restoration tools are required to remove the competitive advantage of these non-natives while also removing the soil legacies they leave behind. Activated carbon (AC) is one such tool, with the ability to disrupt the mechanisms of allelopathy, positive plant-soil feedbacks, and altered nutrient cycling commonly used by non-native species. Previous studies have shown the success of high concentrations of AC in native plant community restoration on a small scale. Here, our goals are twofold: first, to test AC effectiveness in restoring desirable plant communities on a larger scale, and secondly, to identify the primary mechanism, allelopathy versus microbial changes, through which AC impacts native and non-native species. A large scale AC treatment in Methow Valley, Washington tested the effectiveness of AC restoration at a large scale and tested five concentrations and two types of AC to determine lowest effective application. Following treatment, sites were monitored for vegetation cover for three years. The large-scale application produced similar results to the previous study at a 1000 g/m2 application rate, with a 28% increase in the ratio of desirable:undesirable species cover and a decrease to 25% undesirable species cover. However, the effectiveness of AC concentrations below 1000 g/m2 cannot yet be determined and may require a longer time scale and additional monitoring to assess restoration success. A greenhouse experiment was performed, which used native and non-native species common to the study site, grown in pairs in sterilized and live AC-treated soils to separate AC effects on allelopathy from that of microbial interactions. Both native and non-native species experienced a 25% decreased biomass in AC-treated live soils, with a minimal decrease in A- treated sterile soils for native species and no effect in AC-treated sterile soils for non-native species. Overall, AC live soils produced a positive effect on relative abundance; the ratio of native to non-native biomass was highest in AC-treated live soils. From these results, it is concluded that the primary pathway through which AC works is changes in the plant-microbial interactions of both native and non-native species.

Plant growth promoting rhizobacteria (PGPR) are those bacteria that colonise the rhizosphere of various plants and promote growth either directly by improving nutrient uptake by the plant roots or indirectly through the control of pathogens. Due to the negative effects associated with the prolonged use of chemical fertilizers and fungicides, a lot of emphasis is now being given to research that investigates an alternative, sustainable and environmentally friendly method of crop production and protection. In the current study, a collection of rhizobacterial isolates from the University of Pretoria- Plant Growth Promoting Rhizobacteria (UP-PGPR) culture collection were screened for plant growth promotion and biocontrol activity against crown rot caused by Fusarium pseudograminearum on wheat (Triticum aestivum). A seedling tray bioassay was utilised as a rapid small-scale method to screen the rhizobacterial isolates for biocontrol activity against wheat crown rot in the greenhouse. The same method was also used to screen the isolates for direct plant growth promotion of wheat. Of all the isolates (113) screened for wheat crown rot control, 52% (59 isolates) significantly increased the shoot dry weight of the seedlings, 41% (46 isolates) increased the root dry weight of the seedlings, and the total seedling dry weight was increased by 32% (36 isolates) of the isolates. A seedling bioassay was also used to screen the isolates for direct plant growth promotion of wheat. Of the 113 isolates screened, 12% (14 isolates) increased the shoot dry weight of the seedlings, 22% (25 isolates) increased the dry weight of the roots; while the total dry weight of the seedlings was increased by 32% (36 isolates) of the isolates. Subsequent to the seedling bioassay in the greenhouse, the isolates were also assessed in vitro for selected traits associated with biocontrol activity and plant growth promotion. To test for a broad spectrum of biocontrol activity, in addition to F. pseudograminearum, the isolates were also screened for inhibition of Rhizoctonia solani, Phytophthora capsici and Macrophomina phaseolina. Almost 50% of the isolates displayed broad-spectrum activity against the pathogens on three different media. Some notable isolates in this regard were Bacillus sp. strain N54 and Pseudomonas sp. strain N59, N67 and N69. All isolates screened displayed multiple traits associated with biocontrol activity such as the production of antibiotic enzymes, volatiles (NH3 and HCN) and the production of siderophores. The isolates also displayed multiple traits associated with direct plant growth promotion (nitrogen fixation, phosphate solubilization, IAA and ACC deaminase). Based on the results obtained from the seedling bioassays in the greenhouse and the in vitro screening, a scoring system was developed, and the isolates were awarded points. Bacillus sp. strain A09AC, A17, A20, N02, N28, N54 Stenotrophomonas sp. strain A45, Pseudomonas sp. strain N04AC, N44 and N59A were selected for pot trials to confirm their F. pseudograminearum biocontrol efficacy (Figure 1.1). Bacillus sp. strain A10AC, Stenotrophomonas sp. strain A33, A43, A45, Paenibacillus sp. strain KBS1F3, Pseudomonas sp. strain N29, N69, N67, N76 and Pantoea sp. strain N34 were selected for use in pot trials in the greenhouse to confirm their efficacy as wheat growth promoters. The selected isolates were further assessed for biocontrol activity and plant growth promotion in greenhouse experiments. KBS1F3 (Paenibacillus alvei) showed the best results for wheat growth promotion while A17 (Bacillus cereus) gave the best results for biocontrol activity. The effect of temperature, pH, NaCl and different carbon sources on the growth of the isolates was also assessed in vitro. The optimum temperature of all isolates was observed to be between 26oC and 35oC while KBS1F3 was able to grow at 47oC and A17 at 50oC. The growth of KBS1F3 decreased with an increase in NaCl concentration while A17 still grew well at 4% NaCl concentration. All isolates grew optimally at pH 7. KBS1F3 still grew well at pH 8 while A17 showed good growth at all pH values except pH 4. All isolates showed the ability to utilise a variety of carbon sources.
Dissertation (MSc (Agric))--University of Pretoria, 2019.
Microbiology and Plant Pathology
MSc (Agric)
Unrestricted

We have studied the effects of exogenous salt on whole plant and suspension culture cells of the halophytic tomato Lycopersicon pennellii. Under low salt conditions (2.9 dS/M) plants showed enhanced (halophytic) growth (107% of control). At moderate (7.5 dS/M) and high (18.5 dS/M) salt levels, salt stress reduced growth to about 78% and 40% of control respectively. Salt-induced changes in root mRNAs were analyzed via two-dimensional PAGE of cell free translation (CFT) products. We have identified 14 proteins whose levels were enhanced by exogenous salt. One of these proteins was unique to low salt induced halophytic growth. This system allowed for discrimination between proteins up-regulated at all salt levels and those up-regulated only during salt stress induced growth reduction. Ten proteins were identified whose levels were reduced by exogenous salt. Once again, one could identify a subset of proteins whose levels were reduced only under salt stressed conditions. Proteins identified in this study are candidates for roles in growth maintaining stress adaptive metabolism in L.pennellii. These data underscore the complexity of the genetic control of salt metabolism in higher plants. The effects of exogenous salt on protein synthesis and accumulation were studied in suspension cultures of L.pennellii. Two salt levels were applied to the cells. Under low salt conditions (LS, 10 mM), L.pennellii cells showed enhanced (halophytic) growth. Under high salt conditions (HS, 50 mM), the cells showed reduced (salt-stressed) growth. Changes in proteins with time were analyzed by a combination of cell free translation, in vivo labeling and total accumulated protein. In vivo labeling studies showed that the pattern of steady state protein synthesis was disrupted shortly after addition of salt. High salt induced greater disruption in the pattern. Over time, the steady state levels of most proteins shifted back towards those of the unstressed-control. However, the level of several proteins remained altered. Analysis of proteins whose levels increased with exogenous salt showed differences in the response patterns that may allow for discrimination between proteins involved in growth maintaining and stress shock responses.

Petrol and ethanolic extracts of six asteraceous weeds were added to artificial diet and screened for inhibition of larval growth on variegated cutworm, Peridroma saucia (Hbn.). Petrol and ethanolic extracts of Artemisia tridentata and Chamomilla suaveolens and ethanolic extracts of Chrysothamnus nauseosus and Centaurea diffusa were highly inhibitory at five times the naturally occurring concentrations. The two C. suaveolens extracts and the ethanol extract of A. tridentata were active at the natural concentration (100%) and were further examined at 20, 40, 60, and 80% of this level. Inhibition of larval growth was directly related to concentration for each of the three extracts tested. EC₅₀'S (effective concentration to inhibit growth by 50% relative to controls) for the three extracts were 36-42% of the naturally occurring level in the plants. Nutritional indices were calculated for second instar P. saucia feeding on the active ethanolic A. tridentata extract and the petrol extract from C. suaveolens. The relative growth rate (RGR) of P. saucia larvae fed the ethanolic extract of A. tridentata in artificial diet was significantly lower than that in larvae fed diet with the petrol extract of C. suaveolens and larvae on control diet. Dietary utilization was significantly lower for larvae fed the A. tridentata extract. Results of a field trial indicated that a single treatment of A. tridentata extract at the equivalent of 0.2 g/ml could protect cabbage significantly better than the carrier solvent (30% aq ethanol) or distilled water as measured by a visual damage estimate. An insecticide standard, deltamethrin (17.9 µg/1 with 0.4% Superspred TM ), suppressed pest damage significantly better than the A. tridentata-extract treatment. A residual oviposition deterrency to Pieris rapae was found in the field results. Caged experiments in the laboratory confirmed the contact oviposition deterrency of the A. tridentata extract at 0.2 g/ml. Offspring of field-collected P. saucia larvae grew 2.5-fold heavier than larvae from the laboratory colony. However, diet with the A. tridentata extract inhibited both field-collected and laboratory reared saucia larvae equally when compared to their respective controls fed untreated diet. In summary, these results indicate the potential benefit of using specific unrefined plant extracts for growth inhibitors and oviposition deterrents against insect pests. The contribution of individual phytochemicals in the A. tridentata ethanolic extract to growth inhibition or oviposition deterrency is currently speculative.
Land and Food Systems, Faculty of
Graduate

Wastewater or fish effluent (FE) from freshwater aquaculture can be a good and cheap liquid fertiliser for plants. However, while it represents a good source of nutrients to support plant growth in a system called aquaponics, it appears that its use needs to be optimised to take full advantage of the potential benefits. Apart from mineral amendments, the use of beneficial microorganisms that can have a direct impact on plant growth and nutrient utilisation could be a promising option. Plant growth promoting rhizobacteria (PGPR) are a group of rhizospheric bacteria, when introduced in association with the host plant at optimum density, can enhance plant growth and health. One well-known and versatile PGPR is Azospirillum brasilense that has numerous beneficial effects on plants. The production of phytohormones by the bacterium has been proposed as one of the major mechanisms responsible for the plant growth promoting effects observed in plants inoculated with Azospirillum. Hence, this PGPR could be a valuable input in vegetable production under an aquaponics system. In addition, despite the widespread studies conducted with this PGPR in various crops, there is no published report on vegetables fertilised with fish effluent or under an aquaponics system. This study focuses on evaluating the role of PGPR, particularly A. brasilense, on the growth and development of selected vegetable crops fertilised with fish effluent and using an aquaponics system. Strains of A. brasilense Sp7, Sp7-S and Sp245, Herbaspirillum seropedicea and Burkholderia phytofirmans PsJNT were used to inoculate seeds and/or seedlings by soaking and/or drenching. Inoculated and uninoculated seeds and seedlings were germinated and raised in controlled growing cabinets and a greenhouse, respectively. PGPR-inoculated vegetable seeds generally germinated faster and had better early seedling growth than uninoculated controls. Cucumber seeds inoculated with strains Sp7, Sp245 and H. seropedicea exhibited increase in germination percentage and shoot length by 9 and 20%, respectively, while all PGPR improved the germination vigour index, and enhanced length and weight of seedling roots by 25 and 23%, respectively. In tomato, Sp7-S enhanced the germination value, while most PGPR, except Sp7, significantly improved the germination vigour, root length (28%) and weight (37%) with superior vigor. In lettuce, Sp7-S, Sp245 and H. seropedicea inoculation resulted in longer roots (26%). Germination vigour was also improved by inoculation, except for B. phytofirmans. This improved germination and early seedling growth characteristics may influence future crop establishment and production. Of the two laboratory-based inoculation methods used, soaking appeared to be a better technique for enhanced early seedling growth by strains of A. brasilense. This effect could be related to their unique metabolic characteristics of the strains. The growth promoting effects of A. brasilense strains on the early seedling growth of vegetables varied between the bacterial strains and crop species, In particular, strains Sp7-S and Sp245 strongly enhanced root (85%) and shoot (75%) growth, germination value and vigour in tomato when inoculated by soaking. Sp245 increased endogenous plant IAA (indole-3-acetic acid) content of cucumber and lettuce by up to 100%, irrespective of inoculation method. This work demonstrates that the strains can be used for inoculation within the studied range of cell concentrations with or without plant growth promoting (PGP) effects. However, strain Sp7 appeared to be more influential at lower inoculum concentrations (about log10 6), while Sp7-S and Sp245 at log10 7 cfu mL-1 or higher. For instance, cucumber seeds inoculated with Sp7 log10 8 and 6, Sp7-S and Sp245 log10 8 and 7 cfu mL-1 increased seedling growth, vigour index and endogenous plant IAA by up to 55%. In lettuce, the inoculation with log10 6 of Sp7, log10 7 and 6 of Sp7-S, and log10 8 and 7 of Sp245 yielded superior seedling growth with improved seedling vigour, while log10 7 and 8 of Sp7 and Sp7-S, respectively, increased plant IAA concentration by more than 20%. In tomato, Sp7 at log10 6, Sp7-S and Sp245 at log10 7 enhanced the root biomass, while inoculation with all concentrations of Sp7 and Sp7-S, and log10 8 of Sp245 significantly increased plant IAA content by up to 300%. The inoculation with the bacterial cell suspension exerted more beneficial effects on the early seedling growth, vigor and endogenous plant IAA. In cucumber, seeds inoculated with bacterial cell and those treated with IAA solutions produced longer roots and shoots by 163 and 60%, respectively. Seedlings also exhibited superior vigor. These treatments, together with culture supernatant, and combined cell and supernatant, also increased endogenous plant IAA content, in which the combined cell and supernatant produced up to four-fold greater plant IAA concentrations. In lettuce, seeds inoculated with cell suspension produced longer roots (86%) with superior seedling vigour and elevated plant IAA. In tomato, inoculation with cell suspension and treatment with IAA solutions enhanced length of roots length by up to 52 and 188%, respectively, while all treatments significantly increased the plant IAA content by 70%. These results also demonstrate that bacterial cell suspension and combined cell and supernatant showed consistent effects on the expression of plant IAA. This work suggests that the endogenous IAA levels in the seeds during germination have been altered by the activity of live bacteria and phytohormones present in the supernatant. The altered root morphology of the seedlings due to A. brasilense inoculation might have enhanced the capacity of roots to absorb water and essential minerals leading to enhanced plant growth and metabolic activity. For instance, inoculated cucumber seedlings produced longer roots (23%), greater root biomass (19%), higher total phosphorus (15%), endogenous plant IAA (101%) and peroxidase activity (134%). In lettuce, inoculation increased root length (22%), peroxidase activity (53%) and plant IAA (38%). In addition, strain Sp7 enhanced the chlorophyll and protein contents by 25 and 42%, respectively. In tomato, inoculation resulted in longer roots (67%), larger leaves (22%), higher dry matter accumulation (33%), protein (15%) and endogenous plant IAA (94%) contents. Taller seedlings (12%) with larger stems (15%) and more developed leaves (9%) with greater fresh biomass (18%) were observed with Sp7 inoculation, while two-fold increase in peroxidase activity due to strain Sp245 was detected. On the other hand, inoculated basil seedlings grown in soil produced longer roots (90%), taller seedlings (19%) with more (25%) and larger (61%) leaves, which resulted in greater seedling biomass (61%) and phosphorus content (3%), and higher peroxidase activity (122%) particularly for those inoculated with Sp245 and Sp7, respectively. These plant growth promoting effects were also observed in basil grown in an aquaponics system. These include larger stems and leaves (25%), fresh weight yield (17%), peroxidase activity (73%), phosphorus (5%) and protein (23%) contents due to inoculation. The amount of endogenous plant IAA (27%) and chlorophyll (13%) contents were also increased by Sp7 and Sp7-S inoculation, respectively. This further suggests that A. brasilense could be a valuable agent to help maximize the usefulness of fish effluent or wastewater from freshwater aquaculture for vegetable seedling production. The 16S rDNA terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that inoculation with A. brasilense has no adverse effect to the existing rhizobacterial communities (measured by the changes in the distribution of detectable operational taxonomic unit (OTU) (represented by TRF)) in the root rhizosphere of vegetables (i.e. lettuce, cucumber and basil) grown under different systems (i.e. sterile artificial substrate, soil and aquaponics). This highlights that this PGPR did not cause disturbance to the resident microbial communities or imbalance of the normal functioning of the system. In aquaponics, the presence of a substantial density of A. brasilense strains in the root rhizosphere of basil and the enhanced plant growth and physiological parameters of inoculated basil may imply that Azospirillum have successfully established a beneficial association with the existing bacterial populations. Moreover, this study demonstrates the potential of Azospirillum to be a practical agent for enhancing plant growth and development of vegetables fertilised with fish effluent and under aquaponics system. Directing future research endeavors to better understand the basic mechanisms occurring in the Azospirillum-plant interaction rather than exploring large scale application of this PGPR would support further development of the bioinoculant technology.

Plants have been observed to show a range of plastic responses to environmental conditions. For example, the abundance and distribution of nutrients, as well as the presence and proximity of local competition, have been seen to result in changes in root proliferation and architecture. However, whilst some species have been witnessed displaying certain responses under given circumstances, experimental evidence suggests that responses to environmental factors can be far from simple, and sometimes counter-intuitive. Plant responses to components of the environment, and the benefit of such responses, are highly context sensitive. This thesis explores some of the real world complexities that result in the observed responses to hierarchical sets of environmental factors, and presents a theoretical model that seeks to elucidate the interplay between different factors and their effects on “optimal” behaviour by both individuals and populations. Starting with a simple one-dimensional model comprising a linearised approximation of a Gompertz growth function with nutrient patch dependent growth, the individual and combined effects of stochasticity in resource and competitor distribution are investigated. Complexity and functionality are progressively built up, with a resource dependent proliferation response, a scaling up into two-dimensions, and finally different intrinsic plant growth strategies trading growth rate against root system efficiency all introduced and investigated. Throughout the work presented in this thesis, complex and subtle behavioural responses and patterns emerge from seemingly simple models. The importance of stochasticity on individual and population level performance is also highlighted, and the results demonstrate the inability for mean-field approximations and expected results to capture the emergent behaviour.

Thesis (Ph.D.) -- University of Western Sydney, Macarthur, 2001.
A thesis presented to the University of Western Sydney, in partial fulfillment of the requirements for the degree of Doctor of Philosophy, December, 2001. Bibliography : leaves 163-173.

One of the human activities impacting biodiversity is the cutting of old-growth forests. In response to the controversy surrounding the cutting of old-growth in the coastal rainforest of BC, the Ministries of the Environment and Forests have produced biodiversity guidelines that are to be applied when manipulating stands in the provincial forest. This study augments these guidelines by investigating the diversity differences between second-growth and old-growth forests in relation to site quality. We demonstrate how standlevel plant diversity differs between 40-year-old and old-growth stands in the Very Wet Coastal Western Hemlock subzone (CWHvm) on Vancouver Island. This information is intended to provide foresters with an understanding of the effects of age, disturbance and site quality on stand-level plant diversity, thereby allowing for informed professional management decisions.

Aspergillus flavus infection of agriculturally important crops such as tree nuts, maize, peanuts, and cotton has decreased crop value. Researchers have identified three major approaches to combat A. flavus growth and aflatoxin accumulation: identifying natural resistance in crops, genetically engineering crops for enhanced resistance, and introducing an atoxigenic fungal strain as a competitor. In this dissertation, I investigated two of the three means to control A. flavus growth and infection: genetically engineered crops and identification of natural resistance. My studies of natural resistance in cotton crop show that Sa 1595, a Gossypium hirsutum cultivar, is significantly more susceptible to A. flavus infection; however, no significantly resistant cultivars were observed, but I did observe a trend of diminished susceptibility in A2 186 and Tamcot Sp 23. I then examined synthetic antimicrobial peptide, D4E1, as a means to increase resistance in crops. My research shows that D4E1 effectively increases reactive oxygen species (ROS), an apoptosis precursor at concentrations as low as 1 µM. Breaches in the membrane that allow infiltration and subsequent fluorescence from Sytox^® green occur at higher concentrations. Finally, genetically engineered tobacco plants were examined for D4E1 localization. My research shows that the HA-D4E1 construct was present in the most abundance in the chloroplast of plastid transformed plants, while nuclear transformed plants had nuclear localization. All of my findings suggest that cotton crops do not exhibit any significant enhanced natural resistance to A. flavus infection and growth; however, engineering crops with D4E1 will exhibit enhanced crop resistance.

High-throughput phenotyping is an important means to meet the agricultural needs for future food and energy production. This entails an increasing amount of work in Image-based, non-destructive phenotyping systems. This thesis de-scribes a low-cost phenotype collection system for growth chambers, and methods to segment plants from time series images using temporal information. The system uses a webcam to record plant growth in a top-down view with a fixed time interval to create time-lapse images of multiple plants. It has successfully recorded the growth of Arabidopsis thaliana over three months from seedling to flower. The development of plant segmentation methods involves experiments to compare and select the optimal colour space for plant segmentation, and the development of an unsupervised plant segmentation method that is capable of segmenting multiple plant species (e.g. Arabidopsis thaliana, Oats, Oilseed Rape) without relying on knowledge of plant colour. The method is also modified to provide colour-based, superpixel-based and supervoxel-based approaches to the segmentation of plants from time series images.

Harnessing the abilities of soil microbes to improve plant health and productivity may be an important factor in obtaining food security for the future. In this study, 179 potential plant growth-promoting bacteria (PGPB) were isolated from the rhizosphere of five types of plants from three Western Australian soils. On the basis of in vitro plant growth promotion assays, seven isolates were selected for testing in field trials in Western Australia. Two of the PGPB, Burkholderia caledonica NCH45 and Enterobacter soli ANMK1, improved the yield of wheat by 23% and 9% respectively. The isolate, Pseudomonas granadensis PMK4, improved nodulation when co-inoculated with rhizobia on peas by up to 71% and grain yields by 35%. P. granadensis PMK4 was shown to inhabit the nodules of the field grown peas using strain specific primers developed in this study from the 16S-23S rRNA ITS1 region of this isolate. P. granadensis PMK4 was also tested in field trials on Christmas Island on several legume species at three different fertilizer levels (nil, low and high). Significant increases in nodulation and/or plant yields were observed for soybean and mungbean co-inoculated with PMK4 and rhizobia at a low level of applied fertilizer compared with rhizobia only controls. Co-inoculation with PMK4 also significantly increased the copper and phosphorus concentration in the shoots of lablab and soybean at the nil (lablab) and low (lablab and soybean) fertilizer levels. Glasshouse trials using a full phosphorus response curve demonstrated that phosphorus solubilisation is not the mechanism of action by NCH45 and PMK4 in wheat. However, growth pouch assays using the auxin transport inhibitor, 2,3,5-triiodobenzoic acid, indicate that production of indole-3-acetic acid may be at least partly responsible for increasing wheat seedling root lengths. These results support the further testing of the three promising isolates in field trials to determine optimal conditions for improving plant productivity.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.
Plant growth substances and fertilizers from BioHumaNeticsᴿ were evaluated under field conditions on DPL 61 at the University of Arizona Maricopa Agricultural Center in 1985. Treatments included: 1)standard fertilization recommended for the farm, 2)no added fertilizers and 3)a treatment schedule prescribed by BioHumaNetics. No statistically significant differences were detected.

RIASSUNTO Le piante sono fondamentali per il mantenimento del benessere dell’umanità, in quanto forniscono numerosi servizi indispensabili per il mantenimento di un ecosistema correttamente funzionante (Whelan et al., 2005). Entro il 2050, la popolazione mondiale avrà raggiunto più o meno 9 miliardi di persone, quindi le richieste di cibo, di materie prime e di energia rinnovabile aumenteranno drasticamente (Grierson et al., 2011). Per soddisfare questa crescente domanda di beni, è necessaria una forte collaborazione interdisciplinare tra gli scienziati che lavorano per migliorare le colture e gli scienziati che si occupano dell’ambiente, in modo da tradurre specifiche conoscenze di laboratorio in soluzioni pratiche sul campo. In questo contesto, la biologia vegetale svolge un ruolo importante perché consente l'identificazione e la manipolazione di caratteri utili e interessanti che possono essere utilizzati nei programmi di breeding per selezionare nuove linee di colture con caratteristiche desiderabili come una minor necessità di input lasciando invariata la resa, e una maggior adattabilità all’ambiente. Solo lavorando in questa direzione sarà possibile arginare i problemi dell'attuale pratica agronomica come la perdita di biodiversità, il degrado del suolo, l'inquinamento chimico e l'esaurimento delle risorse idriche (Khush, 2001). In particolare, i frutti rappresentano la parte più preziosa della produzione agricola. Infatti rappresentano la parte commestibile di molte colture, comprese quelle utilizzate come frutta da dessert (mele, fragole, uva), come verdure (cetrioli, fagioli, pomodori), come fonti di oli culinari (oliva, olio di palma) o per altri prodotti culinari (vaniglia). I frutti sono importanti anche per la produzione di semi (colza, cereali) e diverse sostanze non commestibili (cotone, oli industriali) e possono essere sfruttati per la produzione di molti altri prodotti, compresi quelli farmaceutici. Da un punto di vista botanico, il frutto è il risultato dello sviluppo dell'ovario dopo l'impollinazione e la fecondazione. Questa struttura rappresenta inoltre una delle principali innovazioni evolutive di Angiosperme (Ferrandiz, 2011). Infatti, i frutti sono essenziali per la riproduzione e l'adattamento delle piante e migliorano notevolmente l'efficienza della dispersione dei semi. La capacità dei semi di germogliare e crescere lontano dalla pianta madre ha consentito alle Angiosperme di colonizzare nuove aree, riducendo il rischio di inbreeding e competizione tra sibling. Il presente lavoro può essere diviso in due diverse linee di ricerca. La prima (primo e secondo capitolo) riguarda la regolazione dell'architettura delle piante e dell'attività dei meristemi negli organismi modello Antirrhinum majus e Arabidopsis thaliana. La seconda invece (terzo e quarto capitolo) rappresenta il progetto principale di questa tesi di dottorato e mira a identificare un solido strumento per la delucidazione dei meccanismi molecolari che controllano la formazione dei frutti in Arabidopsis thaliana. Concentrandosi sulla seconda linea di ricerca, per esplorare i meccanismi che controllano la formazione e la maturazione dei frutti, abbiamo eseguito un'analisi trascrittomica sul tessuto delle valve della siliqua di Arabidopsis thaliana, utilizzando la strategia RNAseq. In tal modo, abbiamo generato un set di dati di geni differenzialmente regolati che aiuteranno a chiarire i meccanismi molecolari che sono alla base della fase iniziale della crescita del frutto, e successivamente della fase di maturazione. La robustezza del nostro set di dati è stata testata atraverso studi di genomica funzionale. Utilizzando un approccio di genetica inversa, abbiamo selezionato 10 geni differenzialmente espressi ed esplorato le conseguenze della loro distruzione sulla crescita e la senescenza delle silique. Abbiamo scoperto che i geni contenuti nel nostro set di dati (codificanti per fattori di trascrizione, proteine del citoscheletro ed enzimi che modulano l'omeostasi degli ormoni) svolgono ruoli essenziali in diversi stadi dello sviluppo e della maturazione della siliqua. Inoltre, dal nostro set di dati, tra i geni down-regolati, abbiamo trovato il gene AUXIN RESPONSE FACTOR 8 (ARF8), il cui trascritto diminuisce costantemente dal primo all'ultimo stadio di sviluppo della siliqua. ARF8 codifica per un fattore di trascrizione che può agire specificamente nel pistillo, in risposta al segnale dell’auxina. L'ormone vegetale auxina regola i principali aspetti dello sviluppo della pianta principalmente attraverso la sua distribuzione differenziale all'interno dei tessuti vegetali. In particolare, ARF8 sembra essere il legame tra il segnale ormonale e il meccanismo molecolare di formazione del frutto (Goetz et al., 2006). In Arabidopsis, la formazione del frutto viene generalmente repressa fino a quando avviene la fecondazione. Tuttavia, nel mutante auxin response factor 8-4 (arf8-4), già precedentemente caratterizzato, sembra che la formazione del frutto sia disgiunta dalla fecondazione, risultando nella formazione di un frutto privo di semi (partenocarpico; Goetz et al., 2006). La struttura che si sviluppa dal pistillo non fecondato del mutante arf8-4, è stata considerata per anni una silique partenocarpica in quanto risulta più lunga del pistillo non fecondato wild-type e presenta un pattern di deiscenza, processo essenziale per l’apertura del frutto maturo e il rilascio dei semi. Nonostante ciò, nel 2010, Carbonell-Bejerano e collaboratori hanno riferito che esiste un processo di senescenza inerente allo sviluppo che include lo sviluppo della zona di deiscenza e che risulta essere indipendente alla fecondazione. Questo processo di senescenza quindi è comune tra pistilli fecondati e non fecondati. In linea con questo studio, i nostri risultati suggeriscono che il mutante arf8-4 non presenta un vero fenotipo partenocarpico ma piuttosto mostra un’alterazione nella regolazione del cross-talk ormonale, probabilmente dovuta a una proteina tronca. Questa alterazione può a sua volta influenzare il coordinamento tra crescita e senescenza del pistillo, modificando quindi la corretta progressione dei processi di sviluppo. Per questo motivo, almeno in Arabidopsis, l'unica caratteristica strutturale che differenzia il frutto parthenocarpic di arf8-4 dal pistillo non fecondato di tipo wild-type è la dimensione aumentata. Ulteriori analisi saranno necessarie per continuare a studiare il fenotipo di arf8-4, incluse analisi molecolari ad alto rendimento (spettrometria di massa) sul contenuto di ormoni nel tessuto delle valve e analisi western-blot per confermare definitivamente la presenza della proteina tronca nelle piante mutanti arf8-4. Referenze Carbonell-Bejerano, P., Urbez, C., Carbonell, J., Granell, A. and Perez-Amador, M.A. (2010) A Fertilization-Independent Developmental Program Triggers Partial Fruit Development and Senescence Processes in Pistils of Arabidopsis. Plant Physiol., 154, 163–172. Ferrandiz, C. (2011) Fruit Structure and Diversity. Encycl. Life Sci. Goetz, M., Vivian-Smith, A., Johnson, S.D. and Koltunow, A.M. (2006) AUXIN RESPONSE FACTOR8 Is a Negative Regulator of Fruit Initiation in Arabidopsis. Plant Cell, 18, 1873–1886. Grierson, C.S., Barnes, S.R., Chase, M.W., et al. (2011) One hundred important questions facing plant science research. New Phytol., 192, 6–12. Khush, G.S. (2001) Green revolution: the way forward. Nat. Rev. Genet., 2, 815–822. Whelan, C.J., Wenny, D.G. and Marquis, R.J. (2005) Ecosystems and Human Well-being: Synthesis. Isl. Press. Washington, DC, 1–137.
ABSTRACT Plants can be consider fundamental for maintaining human well-being, since they provide several benefits that humans freely gain from the natural environment and from properly functioning ecosystems (Whelan et al., 2005). By 2050, the world population will have reached more or less 9 billion people, therefore, the demands for energy-intensive food, shelter, clothes, fibre, and renewable energy will dramatically increase (Grierson et al., 2011). To satisfy such increasing goods demand it requires a strong interdisciplinary collaboration between plant scientists, working to improve crop, and environmental scientists, working on environmental stability to translate the specific knowledge into field-based solutions. In this contest, plant developmental biology has an important role because it allow the identification and manipulation of useful and interesting traits which then can be used for breading programs to select new crop cultivars that need less inputs and are adapted to live in their environment. So they can help to overcome the problems of current agronomic practice like loss of biodiversity, soil degradation, chemical pollution and depletion of water resources (Khush, 2001). Particularly, fruit represent the most valuable part of crop production. Actually, they are the edible part of many crops, including those used as dessert fruits (apples, strawberries, grapes), as vegetables (cucumbers, beans, tomatoes), as sources of culinary oils (olive, oil palm), or for other culinary products (vanilla). Fruits are also important for seed production (canola, cereals) and several non-edible substances (cotton, industrial oils), and can be adapted to the production of many other products, including pharmaceuticals. From a botanical point of view, fruit is the result of the development of ovary after pollination and fertilization and it represent a major evolutionary innovation of Angiosperms (Ferrandiz, 2011). Actually, fruits are essential for plant reproduction and adaptation, and greatly enhance the efficiency of seed dispersal. The ability of the seeds to germinate and grow far away from the parent plant allows Angiosperms to colonize new areas, reducing the risk of inbreeding and sibling competition. The present work can be divided in two different research lines. The first one (first and second chapters) concerns the regulation of plant architecture and meristem activity in the model organisms Antirrhinum majus and Arabidopsis thaliana. The second one (third and fourth chapters) represents the main project of this PhD thesis and it aims to identify a powerful tool for the elucidation of the molecular mechanisms controlling fruit formation in Arabidopsis thaliana. Focusing on the second research line, to explore the mechanisms controlling fruit formation and maturation, we performed a transcriptomic analysis on the valve tissue of the Arabidopsis thaliana silique, using the RNAseq strategy. In doing so, we have generated a dataset of differentially regulated genes that will help to elucidate the molecular mechanisms that underpin the initial phase of fruit growth, and subsequently trigger fruit maturation. The robustness of our dataset has been tested by functional genomic studies. Using a reverse genetics approach, we selected 10 differentially expressed genes and explored the consequences of their disruption for both silique growth and senescence. We found that genes contained in our dataset (encoding for transcription factors, cytoskeletal proteins, and enzymes that modulate hormone homeostasis) play essential roles in different stages of silique development and maturation. Moreover, from our dataset, among down-regulated genes, we found the AUXIN RESPONSE FACTOR 8 (ARF8) gene, whose transcript diminishes steadily from the first time-point to the last. ARF8 encodes for a transcription factor that can act specifically in the pistil, in response to auxin signal. The plant hormone auxin regulates the major aspects of plant development mainly through its differential distribution within plant tissues. Particularly, ARF8 seems to be the link between hormone and molecular mechanism in fruit initiation (Goetz et al., 2006). In Arabidopsis, fruit initiation is generally repressed until fertilization occurs. However, in the already characterized auxin response factor 8-4 (arf8-4) mutant, it seems that fruit initiation is uncoupled from fertilization, resulting in the formation of seedless fruit (parthenocarpic fruit), if fertilization is prevented before anthesis with the removal of anthers (Goetz et al., 2006). The structure that develops from arf8-4 unfertilized pistil, has been considered for years a parthenocarpic silique because it is longer than wild-type unfertilized pistil and it shows a dehiscence pattern. However, in 2010 Carbonell-Bejerano and collaborators reported that there is a developmental senescence program (that includes the development of the dehiscence zone) which is independent form fertilization and so it is in common between seeded and unfertilized Arabidopsis pistils. In line with this study, our findings suggest that arf8-4 mutant has not a real parthenocarpic phenotype but rather it shows a mis-regulation in the hormones crosstalk, likely due to a truncated protein. This alteration can affect the coordination between growth and senescence of the pistil, modifying the correct progression of the developmental processes. For this reason, at least in Arabidopsis, the only structural characteristic that differentiates arf8-4 parthenocarpic fruit from wild-type unfertilized pistil is the increased size. Further analyses will be necessary to continue investigating arf8-4 phenotype, including high-throughput molecular analyses (mass-spectrometry) about hormones content in the valve tissue and western-blot analysis to confirm definitely the presence of the truncated protein in arf8-4 plants. Overall, the main outcome of this work was that the transcriptome-based gene list on the valve tissue of the Arabidopsis thaliana silique represents a powerful tool for the elucidation of the molecular mechanisms controlling fruit formation. References Carbonell-Bejerano, P., Urbez, C., Carbonell, J., Granell, A. and Perez-Amador, M.A. (2010) A Fertilization-Independent Developmental Program Triggers Partial Fruit Development and Senescence Processes in Pistils of Arabidopsis. Plant Physiol., 154, 163–172. Ferrandiz, C. (2011) Fruit Structure and Diversity. Encycl. Life Sci. Goetz, M., Vivian-Smith, A., Johnson, S.D. and Koltunow, A.M. (2006) AUXIN RESPONSE FACTOR8 Is a Negative Regulator of Fruit Initiation in Arabidopsis. Plant Cell, 18, 1873–1886. Grierson, C.S., Barnes, S.R., Chase, M.W., et al. (2011) One hundred important questions facing plant science research. New Phytol., 192, 6–12. Khush, G.S. (2001) Green revolution: the way forward. Nat. Rev. Genet., 2, 815–822. Whelan, C.J., Wenny, D.G. and Marquis, R.J. (2005) Ecosystems and Human Well-being: Synthesis. Isl. Press. Washington, DC, 1–137.

Der Mangel an Nährstoffen im Boden, hauptsächlich an Phosphor (P) und Stickstoff (N), verbunden mit einem hohen Salzgehalt und der generellen Verarmung landwirtschaftlicher Böden , sind ein ernstes Problem für die landwirtschaftliche Produktion weltweit. Daher besteht ein dringender Bedarf an Forschung und Entwicklung geeigneter landwirtschaftlicher Praktiken, um ungünstige Bodenbedingungen zu verringern und wenn möglich die Fruchtbarkeit von Kulturland wiederherzustellen. Die Verwendung von Rhizobakterien, die das Pflanzenwachstum (PGPR) fördern, kann sich bei der Entwicklung von Strategien zur Erleichterung des Pflanzenwachstums unter normalen Wachstumsbedingungen sowie unter abiotischen Stress als nützlich erweisen. Diese Bakterien bieten ihren pflanzlichen Wirten Vorteile, indem sie die Aufnahme von Bodenmineralien fördern und Pflanzen vor schädlichen Umwelteinflüssen schützen. Die vorliegende Arbeit bewertet die Rolle von in Kamerun natürlich vorkommenden PGPR an Mais und untersucht deren Potenzial als Bioimpfstoffe zur Steigerung des Pflanzenwachstums in Kamerun. Wir prüfen die Hypothese, dass einheimische Bakteriengemeinschaften aus Kamerun einen hohen Anteil an Bakterien aufweisen, deren Eigenschaften Kulturpflanzen helfen, mit ungünstigen Bedingungen umzugehen. In der vorliegenden Arbeit wurden dazu Bakteriengemeinschaften der Rhizosphäre von in Kamerun angebautem Mais isoliert und untersucht. Zum ersten Mal erfolgte eine umfassende phylogenetische Zuordnung aller kultivierbaren Bakterien, auf Grundlage ihrer potenziellen Fähigkeiten zur Förderung des Pflanzenwachstums.
Nutrient deficiencies in soil, mainly in phosphorus (P) and nitrogen (N), coupled to salinity and the impoverishment of agricultural soils, are a severe problem for agricultural production worldwide. Therefore, there is an urgent need for research and development of more suitable agricultural practices in order to reduce unfavorable conditions, and if possible, to restore the fertility of cultivated lands. The use of rhizobacteria, which promote plant growth (PGPR), can prove useful in developing strategies to facilitate plant growth under normal as well as under abiotic stress conditions. These bacteria offer benefits to plant hosts by promoting the uptake of soil minerals and protecting plants from environmental stresses. The thesis evaluates the role of native PGPR associated with maize as potential bio-inoculants for plants growth in Cameroon. We hypothesized that native bacterial communities from Cameroon include a high potential of bacteria helping the plant cope with unfavorable conditions. Here, we provide for the first time a comprehensive phylogenetic affiliation of cultivable bacterial communities associated with maize rhizosphere grown in Cameroon in relationship to their potential plant growth-promoting abilities.

A series of studies were conducted to examine the antioxidant status, drought and disease tolerance, and growth response to foliar application of soluble seaweed (Ascophyllum nodosum) extracts (SE) and humic acid (HA; 25% active HA or 2.9% active HA) in tall fescue (Festuca arundinacea Schreb), Kentucky bluegrass (Poa pratensis L.) and creeping bentgrass (Agrostis palusttis Huds.) grown under low (-0.5 MPa) and high (-0.03 MPa) soil moisture environments. Foliar application of humic acid (2.9 % active HA) at 23.7 and 47.4 l/ha improved leaf water status, shoot and root development in tall fescue, Kentucky bluegrass and creeping bentgrass grown under drought. Humic acid (2.9% active HA) at 15.5 l/ha or SE at 326 g/ha significantly reduced dollarspot incidence and improved turf quality in creeping bentgrass. Drought stress induced an increase of antioxidants alpha-tocopherol and ascorbic acid concentrations in the three turfgrass species. In the experiment with Kentucky bluegrass, drought stress increased beta-carotene concentration, but did not significantly influence superoxide dismutase (SOD) activity. Foliar application of humic acid (25% active HA) at 5 l/ha and/or SE at 326 g/ha consistently enhanced alpha-tocopherol and ascorbic acid concentrations, leaf water status, and growth in the three cool-season turfgrass species grown under low and high soil moisture environments. In the experiment with Kentucky bluegrass, application of HA at 5 l/ha plus SE at 326 g/ha also increased beta-carotene content and SOD activity under low and high soil moisture environments. There were close positive correlations between the antioxidant status and shoot or root growth in the three turfgrass species regardless of soil moisture levels. The antioxidant SOD activity, photosynthetic capacity in terms of Fvm690, and chlorophyll content in terms of Fm730/Fm690 exhibited a seasonal fluctuation in endophyte [Neotiphodium coenophialum (Morgan Jones and Gams) Glenn, Bacon, Price and Hanlin] -free and endophyte-infected tall fescue. Application of SE enhanced SOD activity, photosynthetic capacity, and chlorophyll content in tall fescue, especially at 4 weeks after SE treatment. The SOD activity, photosynthetic capacity and chlorophyll content were not significantly influenced by the endophyte infection. A close positive correlation between SOD and photosynthetic capacity during the summer was found in endophyte-free and endophyte-infected tall fescue.
Ph. D.

Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2014
The effects of liquid Kelpak® and Kelpak® Plantit® disk growth regulator on the growth responses of three selected fynbos species were evaluated in this study. The experiment was arranged using a block design, consisting of 270 plant samples. The experiment consisted of three fynbos species, Coleonema album, Erica verticillata and Leucospermum cordifolium. Each species was subjected to three treatments, the control with no applications, liquid Kelpak® and Kelpak® Plantit® disks (hereafter referred to as disks). The control consisted of 10 plants samples, for each of the three species, arranged is numerical order 1-10. The liquid Kelpak® consisted of 40 plant samples. These 40 plants were divided into 4 groups, containing 10 plants and each group having a different treatment with group 1; 300 ml, group 2; 200 ml, group 3; 100 ml and group 4; 50 ml. The disks consisted of 40 plant samples. These 40 plants were divided into 4 groups, containing 10 plants each and each group having a different treatment with group 1, 2 disks, group 2, 1 disk, group 3, ½ disk and group 4 ¼ disk. The objectives of this study were to assess the desired application of Kelpak® by analysing the physiological improvements or growth responses on of Coleonema album, Erica verticillata and Leucospermum cordifolium. Prior to planting, pre-trial measurements were recorded of each individual cutting. A standard ruler was used to measure the root length and shoot length of each plant, measurements were taken in millimetres. The weight of each plant was measured with a Radwag AS 220/C/2 analytical scale in grams. Plant growth, in terms of plant height was measured on a weekly basis. Plant height was measured with a standard ruler, from the surface of the medium to the tip of the tallest leaf. Watering during the trial period was conducted, using a hand held hose with a rosehead sprayer twice a week and during the third month of the trial once a week. Each container received an average of 250 ml of water. The final week of the trial final readings of the plants was conducted. Plants were carefully harvested and their roots were rinsed with tap water. A standard ruler was used to measure the root length and shoot length of each plant. The roots and shoots were then separated with a secateurs from each other. The fresh weight of each root and shoot weighed and recorded. The combined total weight in grams was captured. The roots and shoots were placed in a manila brown paper bag and placed in a laboratory oven at 55°C for 48 hours. The plants were then removed from the oven and the dry weight of each root and shoot weighed. The combined total was also recorded. The results indicated that liquid Kelpak® and Kelpak® Plantit® disk had an effect on the growth of fynbos species at different application rates. Liquid Kelpak® and Kelpak® Plantit® disks had significantly increased the shoot, root growth and total weight of plants in C. album grown in 15 cm pots over an 18 week period. The liquid Kelpak® indicated higher growth rates in the initial growing stages of C. album as the liquid was immediately available to the plant. The Kelpak ® Plantit® disks had better influence on the growth over a longer period as the disk dissolved at a slower rate which eventually became available to the plant. The liquid Kelpak® and Kelpak® Plantit® disks had significantly increased the dry root weight and post-harvest root length of E. verticillata grown in 15 cm pots over a period. The Kelpak® Plantit® disks indicated higher growth rates in the dry root weight of E. verticillata but both the liquid and the disk had a positive effect on the post-harvest root length. The results also indicated that the successful rooting of E. verticillata was attributed to rooting hormone Seradix 2 under greenhouse heating environment. Liquid Kelpak® and Kelpak® Plantit® disks had significantly increased the wet and dry shoot weights, dry root weights and post-harvest wet and dry total plant weights of L. cordifolium grown in 15 cm pots over the growth period. The Kelpak® Plantit® disks indicated higher growth rates in the dry shoot weights of L. cordifolium but both the liquid and the disk had a significant effect on the wet shoot weight. The liquid and the disks were also responsible for the improved dry root weight. The liquid application indicated the best post-harvest wet weight but the disks improved the post-harvest dry weights. It can therefore be confirmed that organic seaweed concentrates such as Kelpak® is effective on the growth development of L. cordifolium.

Thesis (MTech (Agriculture)--Cape Peninsula University of Technology, 2018.
Choumollier (narrow-stem kale) (Brassica oleracea, L.) has been progressively used in recent years as a supplementary forage harvest in many countries with a temperate climate. Boron (B) and calcium (Ca) are the two most important elements for supporting plant structure and function of plasma membranes. Boron nutrition is vital for obtaining high quality yields in vegetables. The main objective of this study was to evaluate the extent to which boric acid concentration can affect growth parameters (plant height, leaf numbers, chlorophyll levels, and leaf size) of Brassica olereacea var. acephala at different stages of growth and development. Treatment comprised of four concentrations of boron (0.3 mg/kg, 0.4 mg/kg, 0.5 mg/kg and 0.6 mg/kg). Yield and physiological growth responses were measured during the course of the study to ascertain effectiveness and influence of boron treatments on the test crops. Leaves of B. oleracea were harvested at weekly intervals (W1, W2, W3, W4 and W5) after each treatment regimen for approximate basic mineral analysis and composition. Soil pH did not vary much among the various orchard blocks tested, regardless of soil depth. Exchangeable cations Na+ and K+ levels did not vary significantly, but Ca2+ and Mg2+ levels fluctuated considerably among orchards analyzed. The Control Orchard exhibited a higher P content than the other orchards. Ca, Mg, Cu and B levels did not vary significantly among the orchards, but Na, Fe and Zn levels were markedly raised in the Orchard treated with 0.3 mg/kg boron) relative to the Control Orchard. Chlorophyll fluorescence was significantly dependent on the treatment dose of boron as compared to control. Chlorophyll fluorescence also increased significantly with the growth period, i.e., the duration following the initial treatment at all doses of boron. Boron at all did not significantly affect leaf count, leaf length and plant height. The work may add to the body of knowledge on the influence of boron on the physiological performance, mineral contents and proximate composition of leaves of the species. Furthermore, the findings may have important applications in achieving high quality yields in vegetable crops.