Tesi sul tema "Root"
Segui questo link per vedere altri tipi di pubblicazioni sul tema: Root.
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Root".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Olsen, Mary. "Cotton (Texas) Root Rot". College of Agriculture, University of Arizona (Tucson, AZ), 2015. http://hdl.handle.net/10150/346609.
Testo completoAbstract (sommario):
Revised 02/2015; Originally published: 2000.The most important disease of woody dicotyledonous plants in Arizona is Phymatotrichopsis root rot (Cotton or Texas root rot) caused by a unique and widely distributed soil-borne fungus, Phymatotrichopsis omnivora. The fungus is indigenous to the alkaline, low-organic matter soils of the southwestern United States and central and northern Mexico.
2
Olsen, Mary W. "Cotton (Texas) Root Rot". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2009. http://hdl.handle.net/10150/144800.
Testo completoAbstract (sommario):
4 pp.Cotton root rot commonly causes a sudden wilt and death of susceptible plants in summer months but may also cause a slow decline, especially at cooler temperatures. So, positive identification of disease by an experienced person is essential. This publication addresses the symptoms, environmental conditions, disease, prevention and control methods, sampling, identifying susceptible plants and the tolerant and immune plants of cotton root rot.
3
Chambers, Susan M. "Phytophthora root rot of chestnut /". Title page, contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phc4449.pdf.
Testo completo
4
West, Jon. "Chemical control of Armillaria root rot". Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386565.
Testo completo
5
Kilby, Michael W. "Phymatotrichum (Cotton Root Rot) Resistant Grape Rootstocks". College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/215735.
Testo completo
6
Mahato, Tilak, Mary Olsen e Ursula K. Schuch. "Controlling Rhizoctonia Root Rot in Bedding Plants". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2004. http://hdl.handle.net/10150/216551.
Testo completoAbstract (sommario):
Rhizoctonia root rot is caused by a soil borne fungus, Rhizoctonia solani and is a serious problem in bedding plants. The objective of this study was to determine the efficacy of three chemical and two biological products for controlling Rhizoctonia root rot in cool season and warm season bedding plants. Experiments were conducted with summer and winter bedding plants in a nursery production and landscape situation. The efficacy of conventional fungicides or biological products to control Rhizoctonia root rot in bedding plant production and simulated landscape growth cannot be evaluated from results of this study because of low mortality of plants.
7
Tyler, Ray, Edith DeRosa, Lee J. Clark e Mary Olsen. "Seed Treatment to Prevent Black Root Rot". College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/219773.
Testo completoAbstract (sommario):
The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.NU-Zone (imazalil) + Nu-Flow ND (TCMTB + Chloroneb), NU-Flow ND, and Vitavax (carboxin) were evaluated as seed treatments with and without in-furrow PCNB. The following was learned: - Vitavax-treated seed got out of the ground faster than the other treatments, which brings out the possibility that NU-Flow or NU-Zone slows germination. - Stands and root development were slightly better when NUZone was present. - NU-Zone + NU-Flow ND seed treatment is not totally effective in controlling black root rot in heavily inoculated soils. - NU-Flow ND alone is the least effective of the treatments. - In-furrow PCNB did not affect yields.
8
Erb, Ronald T. "The effect of roots on the shearing strength of soil". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1119364987.
Testo completo
9
Persson, Lars. "Soil suppressiveness to Aphanomyces root rot of pea /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1998. http://epsilon.slu.se/avh/1998/91-576-5472-7.gif.
Testo completo
10
Xia-Hong, He. "Bio-control of root rot disease in vanilla". Thesis, University of Wolverhampton, 2007. http://hdl.handle.net/2436/15398.
Testo completoAbstract (sommario):
Fusarium oxysporum Schl. var. vanillae (Tucker) Gondon is known to cause root rot in Vanilla planifolia Andrews in most regions where it is grown, including the major plantations in Xishuangbanna, Yunnan Province of China. This is of serious economic concern to the Province since the vanilla flavouring extractable from the beans of the plant is a valuable food product and an important export commodity. There are no fungicides registered for the control of Fusarium root rot and the only available chemical control methods are ineffective and cause serious contamination of the soil. Breeding for resistance is difficult when no dominant gene is known or where little information is available on fungal pathogenicity. Biocontrol is the main alternative for disease control in this crop, an attractive approach because of increasing concerns for environmental protection. The investigation considers two biocontrol strategies: first the introduction of virulent, antagonistic, non-pathogenic strains, closely-related to the pathogen, to overcome pathogenic populations in infected soils; second the use of essential oils with antimicrobial properties when applied to infected soils. Pathogenicity tests have been done on 81 out of 87 F. oxysporum isolates collected in Yunnan Province. Among these, 32 isolates were non-pathogenic and 49 were pathogenic. The pathogenicity results showed the complexity of F. oxysporum in Yunnan. Seventeen isolates were recovered from the Daluo plantation, of which 14 were pathogenic isolates and 3 non-pathogenic isolates; 26 from the Menglun plantation, in which 12 were pathogenic and 14 were non-pathogenic; 18 isolates from the Manjingdai plantation, in which 12 isolates were pathogenic, whilst the other 6 were non-pathogenic and 20 were obtained from the plantation in Hekou i County, of which 11 were pathogenic isolates and 9 were non-pathogenic. Genetic diversity within this population of F. oxysporum has been investigated with respect to vegetative compatibility and to determine the relationship between VCGs and virulence. The VCG results showed that the 87 strains of Fusarium oxysporum f.sp vanillae isolated from Yunnan Province were complex. They could be distributed into 12 different VCGs and that a direct relationship between VCGs group and virulence could not be drawn. Two non-pathogenic strains, ML-5-2 and HK-5b-4-1, have been screened from 87 strains as candidate biocontrol agents by pathogenicity and VCG, which are self-incompatible and closely related to the pathogens. These two strains were effective in vanilla root rot control in controlled environments, but their effects in field experiments were less conclusive. Seven essential oils, which have long been regarded as having inhibitory effects on pathogens in nature, have also been investigated as biocontrol agents. Three oils, cinnamon oil, thyme oil and clove oil, were effective in inhibiting the growth of pathogen in vitro. These oils may develop into useful components of different management strategies with non-pathogenic strains. For the future, consideration will need to be given to the mechanism(s) of the interaction of the antagonistic components with the soil microbe population and host plant and also to appropriate formulation, to take account of soil type, crop status, cultural practices, environmental and economic factors. Biocontrol methods have considerable potential but must be acceptable to farmers as part of an overall crop management programme.
11
Lan, Chinchun. "Analysis of soil-root interaction". Connect to resource, 1985. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1119365654.
Testo completo
12
Spataro, Ilaria. "Generalized root systems". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Cerca il testo completoAbstract (sommario):
Il mio elaborato definisce i sistemi di radici generalizzati mostrandone le proprietà più rilevanti ai fini della classificazione di quelli di rango 2. Inoltre, ci si sofferma sul fatto che quozienti di sistemi di radici generalizzati sono ancora sistemi di radici generalizzati e si dimostra che tutti i sistemi di radici generalizzati di rango 2 sono combinatoriamente equivalenti a quozienti dei sistemi di radici classici.
13
Carman-Goeke, Macy Anne. "Taking Root". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/91405.
Testo completoAbstract (sommario):
This thesis seeks to investigate how architecture can utilize different techniques to introduce people to landscape, specifically those who have an uncomfortable relationship with nature due to inequities in access to quality green space, a cultural distancing from nature due to historical acts of violence, or an increasingly urban and work focused lifestyle. A proposed Visitor Center in Rock Creek Park, in Washington, DC, acts as a slow transition from park to city and back again, breaking the landscape into more digestible pieces before putting it back together as a whole. The building's strategy for introduction can be broken up into two categories, what the building reveals to visitors, and what it tells visitors. The building reveals the surrounding landscape in a rhythmic way of spaces of rest and spaces of activity, utilizing entrances on different levels, screened views,
and glass corners to frame the landscape and topography. It is also designed to reveal the power of the environment, the sun, the rain, and the snow, in weathering the materials and creating a dynamic appearance and exposing the ways in which water runs through the site. In addition to showing the park, the building also is responsible for educating visitors about the important cultural and natural history of the park. The architecture supports the education of visitors in a flexible and non-technological way, using a variety of surfaces to display information to be seen and touched, to encourage the slowing down of minds and bodies to facilitate the transition from the bustling city to the restorative nature of the park. The proposed building utilizes design concepts present in nature and integrates them into the architecture of the building, to create an introductory experience into the landscape that touches the senses and the mind, preparing the visitors to enjoy the park.Master of Architecture
This thesis, Taking Root, seeks to investigate how architecture can utilize different techniques to introduce people to a landscape, specifically those who have an uncomfortable relationship with nature due to inequities in access to quality green space, a cultural distancing from nature due to historical acts of violence, or an increasingly urban and work focused lifestyle. Research shows that time spent in nature improves mental and physical health outcomes, and the disparity of access or quality creates an issue of injustice. A proposed Visitor Center in Rock Creek Park, in Washington, DC, seeks to remedy that by acting as a slow transition from park to city and back again, and down into the canyon and back again. The building’s strategy for facilitating an introduction can be broken up into three categories: how the building relates to the environment, what the building reveals to visitors, and what it tells visitors. First, the building is designed to reveal the power of the environment, the sun, the rain, and the snow, on the façade through the careful selection of materials specifically for their weathering properties. In addition, the use of a native vine allows the building to change colors through the four seasons of the park, and mirror the forest that surrounds it. The combination of these techniques, plus minimizing the environmental impact of the building through stormwater management, a green roof for local pollinators, bird-safe glass, and reducing solar gain exposes the critical relationship between architecture and environment. Secondly, the visitor center reveals the landscape through the adoption of techniques found in nature that facilitate a powerful introduction to a place, and formalizes them into the architecture of the building and experience of the visitors. The techniques to promote familiarity with the park include controlling the pace with a series of long, curving paths and embracing the rhythm of the topography with ramps and the seasons with a pattern of spaces for activity and rest, teasing with glimpses through the tree-like screen and through the glass gills, framing the view into the park. In addition, the building strives to amplify liminal space, a threshold between the old and new, architecture and nature, which exists in the glass corner gills. These corners jutting into the park, lit by a skylight, and fed fresh air by automated ventilation louvers, allows for a person to have a more intimate experience, in a way that really exists outside of the building, but in a way that provides the comfort of familiarity and not being quite all the way in nature either. Finally, the building also is responsible for telling the visitors what they need to know by educating them on the important cultural and natural history of the park. The architecture supports the education of visitors in a flexible and non-technological way, using a variety of surfaces to display information to be seen and touched, to encourage the slowing down of minds and bodies to facilitate the transition from the bustling city to the restorative nature of the park. The proposed building utilizes its interaction with the physical environment, design concepts present in nature to reveal the landscape, and conveys information in a way and pace that is reflective of the way time moves in the park. All three strategies combine to create an introductory experience into the landscape that touches the senses and the mind, preparing the visitors to enjoy and appreciate Rock Creek Park.
14
Sivananthan, Malini. "An examination of the relationship between NO, ABA and auxin in lateral root initiation and root elongation in tomato". Thesis, University of Canterbury. Biological Sciences, 2006. http://hdl.handle.net/10092/1375.
Testo completoAbstract (sommario):
The length of the primary root and the density of lateral roots determine the architecture of the root. In this thesis the effect of NAA, ABA and the NO donor SNP alone as well as the combination of ABA or NAA with SNP on lateral root development was investigated. The interaction between CPTIO, a NO scavenger, and NAA or SNP is also reported. Following preliminary experiments in which it was observed that the aerial part of the seedling influenced LR growth and that there was a possible inhibitory effect of light on cultured root tips, experiments were conducted with excised roots tips in the dark. NAA was shown to have the potential to initiate LRs across a wide concentration gradient with the total number of LRs and initiated lateral root primordia (LRP) remaining constant across the range of concentrations tested. Over the last decade, nitric oxide (NO), a bioactive molecule, has been reported to be involved in the regulation of many biological pathways. The presence of NO in the system provided via sodium nitroprusside (SNP), promoted LRP initiation based on the NAA concentration gradient; but without changing the total LR initiation, that is LRs plus primordia density remained constant along the concentration gradient of NAA. The absence of LR and LRP in the treatments of CPTIO (a NO scavenger) with SNP or NAA suggests that NO regulates LRP initiation triggered by NAA, which is in agreement with the recent paper published after the commencement of this study (Correa-Aragunde et al., 2006). In agreement with previous studies, ABA inhibited lateral root development by reducing LR density and the number of LRs. The experiments with fluridone, an ABA biosynthesis inhibitor, may indicate that endogenous ABA was at sufficient concentrations in the excised root tips to inhibit primordia initiation. In this study, evidence is presented for the first time to show that SNP can relieve the inhibitory effect of ABA on LR density and number of LRs suggesting the NO, released from SNP, acts downstream of ABA. Overall these data confirm a critical role for NO in LR initiation.
15
Omar, Ibrahim. "Biological control of crown and root rot of tomato". Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310952.
Testo completo
16
Beligala, Gayathri. "Screening for Resistance to Phytophthora Root Rot in Lupin". Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1467244910.
Testo completo
17
Hine, Dick, Roy Whitson, Jim Armstrong, Don Howell e Ron Cluff. "Fungicide Evaluations for the Control of Phymatotrichum Root Rot". College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/204052.
Testo completo
18
Downie, Helen. "Application in imaging root trajectories and root-bacteria interactions". Thesis, Abertay University, 2013. https://rke.abertay.ac.uk/en/studentTheses/bc3a83e5-d6fa-45d8-913b-a97e664ae81a.
Testo completoAbstract (sommario):
Biological processes that occur in the soil have important environmental implications. These processes include root growth and microbial interactions with roots and soil particles and they influence the efficiency of crop production and, in turn, global food security. The observation and imaging of these below-ground processes is difficult due to the opacity of soil and so this thesis presents a new artificial soil analogue that is transparent and therefore allows optical imaging. Transparent soil is a 3D matrix of chemically treated particles of the low refractive index fluoropolymer Nafion, water, plant nutrients and air and has water retention and ion exchange properties similar to natural soils. Before imaging, the transparent soil was saturated with a refractive index matched liquid for appropriate transparency. The substrate was used for 3D imaging of living root systems and high resolution imaging of living roots at a cellular level in relation to the fluorescent-labelled Nafion particles of the substrate. Soil physical conditions influence the growth rate and direction of roots. The substrate compaction and particle size range was varied in transparent soil to quantify the effect of these conditions on 3D root trajectories of lettuce plants. Root systems of plants grown in different substrate conditions were imaged and the root lengths were measured along with the curvature and verticality at sequential points along the roots. There was a greater range of root curvatures in substrates with larger particle sizes and deviation from vertical increased with distance along the root. In substrates with different compactions, there was no effect of compaction on the root curvature or verticality measurements, however the measurements were influenced by the distance along the root. Soil microbes were also studied using the transparent soil system. Pseudomonas fluorescens, a plant growth promoting rhizobacteria, associates closely with plant roots and can act as a biocontrol agent by conveying pathogen resistance to the plant. For this reason, the interaction between lettuce roots and GFP labelled P. fluorescens was studied with the aim of quantifying colonisation patterns along the root and the abundance of bacteria in the substrate surrounding the roots. Transparent soil with two different particle size categories was used to investigate if the substrate particle size affected the colonisation of the roots. Imaging of living roots and bacteria was carried out at 3D sample points along the root and adjacent to the root and it was found that there was a greater abundance of bacteria on the roots than in the substrate. There was a consistent base level of bacterial fluorescence in imaging points that did not include roots, regardless of whether or not there was a plant in the sample and the distance from the root. Substrate particle size had no effect on root colonisation.
19
Lee, Jang Hoon. "Effect of fruit removal on carbohydrate concentrations of cantaloupe (Cucumis melo L.) roots in naturally infested soil with Monosporascus cannonballus". Texas A&M University, 2003. http://hdl.handle.net/1969.1/259.
Testo completoAbstract (sommario):
The effect of fruit removal from cantaloupe was studied under field conditions in a soil naturally infested with Monosporascus cannonballus. Fruit removal resulted in greater sugar accumulation in the cantaloupe roots compared to the roots from plants on which the fruits were allowed to develop normally. Individual, total, and combined root carbohydrate levels were greater in plants without fruit than in plants with fruit. Five major sugars (stachyose, raffinose, sucrose, glucose, and fructose) were found in the cantaloupe roots. Stachyose concentrations were higher than all the other sugars in the cantaloupe roots. Disease severity on the cantaloupe roots with fruit removed was less severe than on roots of plants with fruit, and dry weights were higher in the fruit removal treatment than those of the fruit non-removal treatment.
Fruit removal results in increased root growth and carbohydrate accumulation in the cantaloupe roots. Root sugar concentrations affected infection efficiency and disease progress of Monosporascus root rot and vine decline. Therefore, the retarded development of Monosporascus root rot and vine decline is associated with a greater carbohydrate accumulation in the cantaloupe root.
20
Stevens, Glen N. "Trophic dynamics in the fine-root based food web: integrating resource heterogeneity, root herbivores, and root foraging". Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28168.
Testo completoAbstract (sommario):
Resources in the soil are heterogeneously distributed. We know that plant species differ in their root responses to nutrient patches and that these differences in foraging can influence plant competition. However, most studies of root-resource interactions overlook the potential top-down influence of root herbivores. While root herbivores can influence plant community structure, the extent to which they influence ecosystem-scale factors such as net primary production is unclear. In addition, little is known regarding root herbivore foraging behaviors and, more importantly, whether these foraging behaviors can actually influence species interactions. In this dissertation, I present a conceptual model of soil-root-herbivore interactions in which soil resource heterogeneity structures both root dynamics and the abundance and influence of root herbivores. I conducted two field and one greenhouse experiment examining this proposed model. The dissertation includes an introductory chapter (Chapter 1), a field study examining root responses to manipulations of soil fertility and root herbivory (Chapter 2), a greenhouse study that used plant species responses to heterogeneity to develop predictions about the role of root herbivores in mixed-species neighborhoods (Chapter 3), and a field study of planted communities examining soil fertility and fauna effects on above- and belowground structure and function (Chapter 4). In all cases, there were significant effects of root herbivores on community structure and components of net primary production. Resource distribution had a strong effect in studies conducted in sandy, nutrient-poor soils (Chapter 2 and 3), but had a reduced effect in the study conducted at Kentland Farm in loamy soils (Chapter 4). Interactions between resource availability and root herbivory were common. These results support the theory that the potential benefit of resource-rich patches may be constrained by root herbivores. This research complements recent findings that demonstrate other potential costs of species foraging behaviors (such as exposure to soil anoxia and increased drought stress), as well as potential effects of root herbivores and other soil fauna on plant diversity.Ph. D.
21
Meyer, Jack Robert. "Cultivar susceptibility and fungicide control of black dot root rot". Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/meyer/MeyerJ0507.pdf.
Testo completo
22
Linde, Alec Robert 1956. "Root rot of hydroponically grown lettuce caused by Phytophthora cryptogea". Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277895.
Testo completoAbstract (sommario):
In April 1989, lettuce (Lactuca sativa L.) plants showing severe root rot symptoms were received for diagnosis from a commercial hydroponic facility in Southern California. A species of Phytophthora was consistently isolated from necrotic roots. Pathogenicity trials were conducted under hydroponic conditions in a greenhouse at root temperatures of 18 and 28 C. Root necrosis, along with stem decay and plant death, occurred within 5-7 days after inoculation at both temperatures. Reisolation of the fungus from roots and stems of inoculated, but not from roots of non-inoculated plants, confirmed pathogenicity. The fungus was identified as Phytophthora cryptogea Pethybr. and Lafferty on the basis of cultural and morphological characteristics. However, crosses with A1 and A2 mating types of Phytophthora cryptogea and other species of Phytophthora were not successful. This is the first report of Phytophthora as a root pathogen of cultivated lettuce.
23
Chittem, Kishore. "Genomics and Management of Fusarium Root Rot of Field Peas". Diss., North Dakota State University, 2012. https://hdl.handle.net/10365/26475.
Testo completoAbstract (sommario):
Dry Pea or field pea (Pisum sativum L.) is an important cool season legume crop grown in the United States. Field peas are vulnerable to many diseases of which, soil borne diseases including wilt and root rot are of major economic importance and can cause significant reduction in yield. There is a dearth of satisfactory methods for control of root rot and no varieties with complete resistance to Fusarium root rot are currently available. Root rot disease was found to be prevalent in all the major pea growing counties of North Dakota surveyed in 2004, 2005, 2010 and 2011. Fusarium species were the most frequently isolated fungal species from the infected pea roots of which, F. oxysporum and F. avenaceum were the most common. 21 Field pea varieties were screened for resistance against F. avenaceum and F. solani f. sp. pisi, the Fusarium species traditionally associated with root rots of field pea in growth chamber experiments and field trials. Low levels of resistance were detected in a few cultivars but no variety was found to be completely resistant to any of the pathogens tested. Efficiency of precipitated calcium carbonate (PCC) in controlling Fusarium species most commonly associated with root rots was evaluated under in vitro and field conditions. Significant reduction in spore production, spore germination, and dry mycelial weight of Fusarium spp. were detected on PCC amended media in laboratory studies. In greenhouse and field experiments significant reduction in root rot disease severity was observed with PCC application compared to control. Fungal gene expression in artificially infected field pea roots and F. graminearum grown in culture was assessed using the Illumina mRNA-Seq technology. A total of 613 F. graminearum genes were found to be differentially expressed in planta on pea. Functional classes associated with amino acid metabolism, nitrogen metabolism, extracellular polysaccharide degradation, detoxification by degradation and defense related proteins were found to be significantly enriched in the up-regulated gene set as determined using FunCatDB. Expression of four up-regulated genes was confirmed by RT-PCR to validate the inferences from the sequencing results.
24
Samils, Nicklas. "Monitoring the control methods of Heterobasidion annosum s.l. root rot /". Uppsala : Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2008. http://epsilon.slu.se/200847.pdf.
Testo completo
25
Young, Deborah, e Michael Matheron. "Control of Phytophthrowa Root and Crown Rot of Apple Trees". College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/215717.
Testo completo
26
Matheron, Michael, Deborah Young e Joe Matejka. "Root and Crown Rot of Apple Trees Caused by Phytophthora". College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/215738.
Testo completo
27
Dhillon, Sameet. "The Delicate Root". Thesis, Boston College, 2015. http://hdl.handle.net/2345/bc-ir:104023.
Testo completoAbstract (sommario):
Thesis advisor: Sue RobertsA collection of stories that explore the lives of men and women struggling with love, friendship, growing up and facing the world; all through the lens of Indian culture. Some of these characters are recent immigrants, some have lived in America for years. Regardless, they struggle with issues that are both connected to and separate from their status as Indian Americans. Here we have missed connections and realities. A desire to know as well as a desire to remain in the dark
Thesis (BA) — Boston College, 2015
Submitted to: Boston College. College of Arts and Sciences
Discipline: Departmental Honors
Discipline: English
28
Zamboni, Giulio. "Fan root aerodynamics". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611841.
Testo completo
29
Ingram, Amanda. "Root: early memoirs". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555430230053347.
Testo completo
30
Mazzon, Andrea. "Processo Square Root". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3834/.
Testo completo
31
Olsen, Mary W. "Root-knot nematode". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2011. http://hdl.handle.net/10150/146969.
Testo completoAbstract (sommario):
3 pp.Originally published: 2000
Nematodes are microscopic round worms found in many habitats. They are the most abundant multicellular organisms on earth. Most are beneficial memebers of their ecosystems, but a few are economic parasites of plants and animals. There are several plant parasitic nematodes that cause problems on landscape and garden plants in Arizona and the most widespread and economically important are the root-knot nematodes. This article discusses the hosts and environmental conditions, symptoms and disease of root-knot nematode, and the prevention / control method to it.
32
Blume-Werry, Gesche. "The hidden life of plants : fine root dynamics in northern ecosystems". Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-124757.
Testo completoAbstract (sommario):
Fine roots constitute a large part of the primary production in northern (arctic and boreal) ecosystems, and are key players in ecosystem fluxes of water, nutrients and carbon. Data on root dynamics are generally rare, especially so in northern ecosystems. However, those ecosystems undergo the most rapid climatic changes on the planet and a profound understanding of form, function and dynamics of roots in such ecosystems is essential. This thesis aimed to advance our knowledge about fine root dynamics in northern ecosystems, with a focus on fine root phenology in natural plant communities and how climate change might alter it. Factors considered included thickness and duration of snow cover, thawing of permafrost, as well as natural gradients in temperature. Experiments and observational studies were located around Abisko (68°21' N, 18°45' E), and in a boreal forest close to Vindeln (64°14'N, 19°46'E), northern Sweden. Root responses included root growth, total root length, and root litter input, always involving seasonal changes therein, measured with minirhizotrons. Root biomass was also determined with destructive soil sampling. Additionally, aboveground response parameters, such as phenology and growth, and environmental parameters, such as air and soil temperatures, were assessed. This thesis reveals that aboveground patterns or responses cannot be directly translated belowground and urges a decoupling of above- and belowground phenology in terrestrial biosphere models. Specifically, root growth occurred outside of the photosynthetically active period of tundra plants. Moreover, patterns observed in arctic and boreal ecosystems diverged from those of temperate systems, and models including root parameters may thus need specific parameterization for northern ecosystems. In addition, this thesis showed that plant communities differ in root properties, and that changes in plant community compositions can thus induce changes in root dynamics and functioning. This underlines the importance of a thorough understanding of root dynamics in different plant community types in order to understand and predict how changes in plant communities in response to climate change will translate into root dynamics. Overall, this thesis describes root dynamics in response to a variety of factors, because a deeper knowledge about root dynamics will enable a better understanding of ecosystem processes, as well as improve model prediction of how northern ecosystems will respond to climate change.
33
Mayer, Sebastian. "Hilbert modular forms for the fields Q([square root]5), Q([square root]13) and Q([square root]17)". [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985767022.
Testo completo
34
佑脩, 田和, e Yusuke Tawa. "Dynamics and architecture of fine root system in a Cryptomeria japonica plantation". Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13106238/?lang=0, 2019. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13106238/?lang=0.
Testo completo
35
Ihrmark, Katarina. "Double-stranded RNA elements in the root rot fungus Heterobasidion annosum /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2001. http://epsilon.slu.se/avh/2001/91-576-6310-6.pdf.
Testo completo
36
Popoola, Temi-Tope Olukayode. "The role of host plant stress in Armillaria root rot infections". Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304388.
Testo completo
37
Collins, A. J. "'The role of willow root architecture and character in root reinforcement potential'". Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246876.
Testo completo
38
Morandage, Shehan [Verfasser]. "Characterization of Root System Architectures from Field Root Sampling Methods / Shehan Morandage". Bonn : Universitäts- und Landesbibliothek Bonn, 2020. http://d-nb.info/1221668927/34.
Testo completo
39
Upton, Caroline. "Factors controlling root growth in heterogeneous substrates : physical structures and root behaviour". Thesis, Abertay University, 2016. https://rke.abertay.ac.uk/en/studentTheses/f556f1fc-0529-4555-b985-320f853780c6.
Testo completoAbstract (sommario):
Roots are essential for nutrient uptake and anchorage for the plant, however there is published evidence to suggest that the physical structure of soil has a strong influence on their abilities to grow and develop healthily. Observing roots in 3-dimensions, in situ and non-destructively is important for understanding the complex nature of the physical root/soil relationship, however roots are notoriously difficult to observe due to the opaque nature of soil. This problem can be partially negated by using techniques such as X-ray micro-computed tomography, but is an expensive and time-consuming technique. Furthermore, soil is a growth medium prone to spatial and temporal variation in terms of water, nutrient availability, and microbial populations, making it difficult to observe the effects of soil physical structure alone. The development of transparent soil (TS) by Downie et al. (2012) has brought about a new era in the study of root/soil interactions. TS is a growth medium with the transparency of agar and some of the physical heterogeneity of soil. TS has particles and pores, so roots can explore it in much the same way as they would soil, however the water and nutrient levels can be better controlled and microbial influences are less of an issue, due to the semi-sterile conditions that transparent soil cores are kept under. Downie et al (2012) used TS to study root growth of small Arabidopsis thaliana roots and also imaged Psuedomonas fluorescens colonising lettuce seedling roots. This project scaled the TS system up in order to image larger root systems of Hordeum vulgare (barley) seedlings under different physical conditions. Comparisons of barley roots growing in soil and TS were made, and it was found that roots grew longer in natural soil than in TS. The TS was then sieved into different particle size ranges and it was found that barley roots grew more successfully in the smaller particles (850-1250 μm) than the larger particles (>1676 μm). Vertically stratified split pots, containing large particles down one side and small particles down the other were also used and non-destructively imaged at 24-hour intervals. It was found that the presence of the large particles had an inhibitory effect on root growth across the entire root system, including the roots that were growing in the smaller particles. Finally a device was designed which allowed the application of compression to the TS system. It was found that root growth decreased proportionally with the level of pressure that was applied to the TS cores. Manipulation of TS structure and the development of techniques to quantitatively record root growth and physical soil conditions from 3-D images has enabled us to measure root growth in barley roots under different physical conditions. The results showed that root growth is heavily influenced by particle size, pore structure and soil strength. Root/soil contact was consistently observed as an important soil property for root growth across experiments.
40
Eskiyerli, Mirat Hayri. "Square root domain filters". Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299973.
Testo completo
41
Schofield, April. "Blood At The Root". TopSCHOLAR®, 2015. http://digitalcommons.wku.edu/theses/1450.
Testo completoAbstract (sommario):
This is a coming of age story about two very different boys – Jason, a Northerner who ends up stuck in a small Southern town and Billy, a Southern boy with an abusive father. The boys become friends and grow up learning the dark secrets that are allowed to fester in a tiny southern town ruled by the Good Ol’ Boy System of justice. The story chronicles how their shared experiences change them in ways they never imagined and ultimately destroys their friendship and their lives. Through a history of violence and prejudice, Billy and Jason learn who they really are and just how far they’re willing to go to get what they want. They discover the true meaning of strength and weakness and how to survive in a world where they don’t fit in. The story explores the issues of violence, drug abuse, and murder that often lie hidden beneath the façade of fanatic Christianity, propriety, and status in seemingly innocent, charming Southern towns.
42
Birdsall, Margaret. "Root development in allium". Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328252.
Testo completo
43
Hopkins, Samuel F. "Root system chip-firing". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/117780.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mathematics, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 195-200).
This thesis investigates an extension of the classical chip-firing process to "other Cartan-Killing types." In Chapter 1 we review the classical chip-firing game: the states of this process are configurations of chips on the vertices of a graph; the transition moves are firings whereby a vertex with at least as many chips as neighbors may send one chip to each neighbor. A fundamental property of chip-firing is that it is confluent: from any initial configuration, all sequences of firings lead to the same terminal configuration. In Chapter 2 we discuss Propp's labeled chip-firing process on the infinite path, for which confluence becomes a subtler question. We prove that labeled chip-firing is confluent starting from an even number of chips at the origin (but not from an odd number). In Chapter 3 we reinterpret labeled chip-firing as a process on the weight lattice of a root system, where the firing moves consist of adding a positive root whenever the weight we are at is orthogonal to that root. We call this the central-firing process. We give conjectures about certain initial weights from which central-firing is confluent. We also prove that central-firing is always confluent from all initial weights if we mod out by the action of the Weyl group, thereby giving a generalization of unlabeled chip firing on the infinite path to other types. In Chapter 4 we introduce some remarkable deformations of the central-firing process which we call the symmetric and truncated interval-firing processes. These are analogous to the Catalan and Shi hyperplane arrangements. We prove that these interval-firing processes are always confluent from all initial weights. In Chapter 5 we study the set of weights with given interval-firing stabilization. We show that the number of weights with given stabilization is a polynomial in our deformation parameter. We call these polynomials the symmetric and truncated Ehrhart-like polynomials, because they are analogous to the Ehrhart polynomial of a polytope. We conjecture that the Ehrhart-like polynomials have nonnegative integer coefficients. In Chapter 6 we prove "half" of this positivity conjecture by providing an explicit, positive formula for the symmetric Ehrhart-like polynomials.
by Samuel Francis Hopkins.
Ph. D.
44
Koerfer, Filip. "Classification of Root Systems". Thesis, Uppsala universitet, Algebra och geometri, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355873.
Testo completo
45
Reffruschinni, Katie, David Robinson e Albert Dobrenz. "Seedling Alfalfa Root Research". College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/203792.
Testo completoAbstract (sommario):
There has been limited research on the rooting patterns of alfalfa. This information would be important in developing new germplasm sources that are more water efficient, salt tolerant and drought tolerant. Ten alfalfa varieties were evaluated for possible genetic control of rooting traits. Seedlings were grown hydroponically in a growth chamber. The cultivars evaluated showed a significant statistical difference for width of lateral root system and number of lateral roots. The variation in seedling rooting patterns is sufficient to warrant a selection program for improved lateral rooting patterns.
46
Brigham, Lindy Andersen 1951. "Root border cell differentiation". Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290689.
Testo completoAbstract (sommario):
The inability of a plant to run from danger or seek nutrients necessitates its capacity to change the environment of the surrounding soil for protection and sustenance. A unique plant process, the release of thousands of autonomous cells from the root cap, called root border cells, may play a role in the ability of the plant to regulate microbial populations and nutrient availability in the rhizosphere. In this study, evidence is presented showing that root border cells are a differentiated tissue, that the production of border cells is highly regulated and tied to cell turnover in the root cap and that products of border cells regulate cell division in the root cap meristem. In vivo labeling experiments demonstrate that 13% of the proteins that are abundant in preparations from border cells are undetectable in root tip cells. Differences between the two cell populations are apparent as soon as border cells separate from each other, even when they are still adhered to the root tip. Twenty-five percent of the proteins synthesized by border cells in a 1-hour period are rapidly excreted into the incubation medium. Border cells arise within the root cap meristem by cell division and their production is tightly regulated both developmentally and in response to border cell removal. Removal of border cells results in the induction of cell division in the transverse root cap meristem to 400% of the basal rate within 30 minutes. This elevated rate of mitosis is maintained for 1.5 h and falls to basal levels within 6 hours. During this time, mitosis in the root apical meristem remains constant. mRNA differential display analysis showed changes in gene expression in the root cap within 5 to 15 minutes of removal of border cells. Genes putatively involved in cell functions in three regions of the cap showed expected distribution patterns by in situ hybridization and RNA blot analysis revealed changes in their expression patterns were seen in response to border cell removal. The presence of border cells acts as an inhibitor to continued mitosis and border cell production in the root cap. Evidence from fractionation studies shows that a heat stable, protease insensitive molecule in the range of 25 to 80 kDa, produced by the border cells themselves, is responsible for this inhibition.
47
Smith, Lisa C. "The root in winter". Thesis, University of St Andrews, 1994. http://hdl.handle.net/10023/14359.
Testo completoAbstract (sommario):
Factors affecting the survival of over-wintering tree roots during waterlogging were investigated. Die-back of roots covered by high Winter water tables results in shallow rooted trees susceptible to wind-throw. Such is the scale of the problem in Britain, this research is considered to be of practical relevance. Sitka spruce (Picea sitchensis (Bong.) Carr.) and Lodgepole pine (Pinus contorta Douglas ex Loudon) were chosen, being the most predominant species planted and showing differing susceptibility to flooding. Sitka spruce is considered flood-intolerant (Crawford 1982) and Lodgepole pine highly-tolerant (Minore 1968). In both species, waterlogging the whole root system for 3 months severely reduced the carbohydrate content of the distal 15cm root, reflecting almost total depletion of starch reserve and varying degrees of glucose depletion. In Sitka spruce, depletion depended on the date of flood-initiation, being most severe after flooding from October when root respiration rate was higher, rather than November as the roots became dormant. Flooding injury was reflected in decreased tri-phenyl tetrazolium chloride reduction and loss of respiratory capacity. Greater loss of aerobic (as compared to anaerobic) respiration capacity after flooding suggested damage to the aerobic pathway, either directly through anoxia or indirectly due to depletion of sugars important in cell maintenance. Injury appeared to be greater when respiratory activity at flood-initiation was high. Aeration from stem lenticels ameliorated flood-injury and carbohydrate depletion in Lodgepole pine, although the roots appeared to have no metabolic adaptation to anoxia. Increased soil temperature during Winter flooding increased carbohydrate depletion in the distal root and reduced viability relative to seedlings flooded at ambient temperature. Carbohydrate depletion during cold storage and its effect on survival of soil waterlogging at out-planting was determined in Sitka spruce. Cold storage leads to increased root growth and slightly superior flood-tolerance when compared to nursery over-wintered seedlings, presumably due to the more dormant state of stored seedlings.
48
Zhang, Li. "Grapevine root growth under water stress and its relationship to root water uptake". Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0893.
Testo completoAbstract (sommario):
Le sujet de l’adaptation aux changements climatiques est devenu l’un des sujets contemporains les plus importants dans la vigne. Une grande focalisation a été mise sur la compréhension des effets du porte-greffe sur la croissance du scion, l’absorption des nutriments, et la tolérance au stress, dans l’objectif final de développer de nouveaux porte-greffes qui facilitent l’adaptation au changement climatique. L’objectif de cette thèse est d’examiner comment les différences dans la résistance à la sécheresse entre les génotypes peut résulter en de grandes différences dans leur capacité à maintenir leur croissance racinaire en situation de stress. Une meilleure compréhension sur la manière dont la structure, la croissance racinaire et l’absorption d’eau répondent au stress nous permettra de mieux comprendre quels sont les aspects de la physiologie racinaire qui contribuent à la tolérance face à la sécheresse. Des recherches précédentes qui s’étaient focalisées sur l’absorption d’eau racinaire chez la vigne ont suggéré que l’absorption d’eau racinaire pouvait être fortement liée à la vitesse de croissance racinaire instantanée (voir Gambetta et al. 2013). Cette observation implique que des différences entre les génotypes dans la résistance face à la sécheresse pourrait largement résulter de leur capacité à maintenir la croissance racinaire en conditions de stress. Deux porte-greffes de vigne avec des capacités contrastées en matière de résistance à la sécheresse, le Riparia Gloire de Montpellier (RGM) et le 110 Richter (110R) ont été sélectionnés pour étudier dans cette thèse. RGM est considéré comme sensible à la sécheresse, tandis que 110R est fortement résistant à la sécheresse (Carbonneau 1985). La thèse a examiné la relation entre la croissance racinaire et la capacité de résistance à la sécheresse en évaluant la vitesse de croissance racinaire, la conductivité hydraulique à travers deux variétés de porte-greffe en conditions de déficit en eau. Le niveau de l’expression des gènes d’aquaporines (via la qPCR et l’ARNseq) et leur contribution à la conductivité hydraulique racinaire ont été analysés dans les radicelles afin d’obtenir une meilleure compréhension sur les mécanismes impliqués dans la régulation de l’absorption de l’eau racinaire et la conductivité hydraulique au cours du développement et en réponse à un manque d’eau.Le traitement de stress d’eau prolongé a diminué le potentiel hydraulique de la plante. La croissance racinaire individuelle est très hétérogène : bien que le traitement de sécheresse réduise l’élongation racinaire en moyenne, la vitesse de croissance racinaire varie tout de même énormément. Un haut niveau de stress hydrique a réduit significativement la vitesse de croissance racinaire moyenne à la fois pour RGM et 110R. Globalement, la vitesse de croissance racinaire moyenne a montré une tendance réduite au cours du développement de la plante. La température du sol est aussi un facteur qui affecte la croissance racinaire. Pour RGM et 110R, en conditionsIIde bon arrosage et de stress hydrique, la vitesse de croissance quotidienne moyenne a été positivement corrélée avec la température du sol quotidienne moyenne. En conditions de bon arrosage, des vitesses de croissance racinaires plus importantes ont été constamment observées chez 110R par rapport à RGM, ce qui pourrait être une explication possible de sa meilleure résistance à la sécheresse par rapport à 110R. [...]The subject of adaptation to climate change has become one of the most important contemporary topics in grapevine. Much focus has been placed on the understanding of rootstocks effects on scion growth, nutrient uptake, and tolerance to stress, with the ultimate goal of developing novel rootstocks that facilitate adaptation to a changing climate. The purpose of this thesis is to examine how differences in drought resistance between genotypes could result largely from differences in their ability to maintain root growth under stress. A better understanding of how root structure, growth, and water uptake respond to stress will allow us to better understand what aspects of root physiology contribute to drought tolerance. Previous research focused on root water uptake in grapevine suggested that root water uptake could be tightly coupled to a root’s instantaneous rate of growth (see Gambetta et al. 2013). This observation implies that differences in drought resistance between genotypes could result largely from their ability to maintain root growth under stress. Two grapevine rootstocks with contrasting drought resistance capacity, Riparia Gloire de Montpellier (RGM) and 110 Richter (110R), were selected to study in this thesis. RGM is considered as sensitive to drought, while 110R is highly resistant to drought (Carbonneau 1985). The thesis examined the relationship between root growth and drought resistant capacity by assessing root growth rate, hydraulic conductivity across two rootstock varieties subjected to water deficit. The role of aquaporin gene expression (via qPCR and RNAseq) and their contribution to root hydraulic conductivity were analyzed in fine roots in order to obtain a better understanding on the mechanisms involved in the regulation of root water uptake and hydraulic conductivity across development and in response to water deficit.Prolonged water stress treatment decreased plant water potential. Individual root growth is very heterogeneous, although drought treatment reduces root elongation on average, individual root growth rate still varies enormously. High level of water stress significantly reduced average root growth rate for both RGM and 110R. Globally, average root growth rate showed a decreased trend over plant development. Soil temperature is also a factor that affects root growth. For both RGM and 110R, under both well-watered and water-stressed conditions, average daily root growth rate was positively correlated with average daily soil temperature. Under well-watered conditions, higher root growth rates were constantly observed in 110R compared to RGM, which could be one possible explanation for the higher capacity in drought resistance of 110R.Root hydraulic conductivity (Lpr) was influenced by both water stress treatment and plant developmental stage. Generally, for both RGM and 110R, Lpr was significantly reduced under water stress in early stage. In mid and late stages, no significant differences in Lpr were observedIVbetween well-watered and water-stressed plants. Changes in individual root Lpr in response to pre-dawn leaf water potential (ᴪpredawn) were investigated as well. Lpr showed a fast drop in the beginning of water stress treatment when ᴪpredawn was higher than -0.5 MPa. However, with ᴪpredawn getting more negative, e.g. from -0.4 MPa to -2.0 MPa, the range of Lpr values measured in our study maintained constant. Lpr of well-watered plants decreased as well even though their ᴪpredawn was maintained at a high level (< 0.1 MPa) during the period of the experiment. [...]
49
Taheri, Abdolhossein. "Interaction between root lesion nematode, Pratylenchus neglectus, and root-rotting fungi of wheat". Title page, contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09pht128.pdf.
Testo completoAbstract (sommario):
Bibliography: leaves 307-329. This study concludes that in soils in South Australia where root-rotting fungi and P. neglectus exist together, root disease of wheat is caused by their combined effect. Evidence suggests that P. neglectus not only contributes to this interaction through mechanical wounding of roots, but also causes biochemical and physiological changes in plants, making them more prone to fungal infection.
50
Schmidt, Sonja. "Root responses to soil physical conditions and the role of root-particle contact". Thesis, Abertay University, 2011. https://rke.abertay.ac.uk/en/studentTheses/ab0e3468-93c7-40ab-8809-48c41cf5caa2.
Testo completoAbstract (sommario):
This thesis considers the elongation of root and shoots in relation to matric potential and soil strength in contrasting species. The role of root-particle contact for root and shoot elongation in relation to particle/aggregate size and bulk density at various matric potentials is discussed. Root and shoot elongation of maize and lupin in soil and vermiculite at matric potentials ranging from -0.03 MPa to -1.6 MPa were investigated. Both root and shoot elongation rate of maize and lupin were significantly slower in vermiculite than in soil (p < 0.001). As vermiculite has very different particle size distribution and hydraulic properties from soil, the degree of contact between root and vermiculite was thought to provide a possible explanation for the slower elongation rates. A new method was developed to quantify root-particle contact using X-ray microtomography and verified using ‘phantoms’ (model systems of known dimensions). Root-particle contact was approximately 25 % greater in soil than in vermiculite. The greater root-particle contact in soil was thought to provide better growth conditions than in vermiculite. Root and shoot elongation were examined when plants were place in humid air above an osmotic solution (KC1) to evaluate the degree to which root elongation could occur in the absence of solution contact. No significant shoot elongation occurred and root elongation was more reduced than in vermiculite. Hairless maize and barley mutants and their wildtypes were used to investigate further the effects of root-particle contact when water availability is limiting in both soil and vermiculite systems. Root elongation rates of the hairless mutants were slower than those of the wildtypes, when the growth medium was wetter than -1.6 MPa. However the reduction in root elongation of hairless maize may have been due to pleiotropic effects slowing the elongation (the elongation rate relative to the maximum elongation rate was not significantly different). The combined effects of mechanical impedance and decreasing matric potentials on root and shoot elongation were tested. Maize and lupin were grown in soil packed to five bulk densities (bulk densities 1.1, 1.2, 1.3, 1.4 and 1.5 g cm'3) and wetted to three matric potentials ranging from -0.01 MPa to -1.2 MPa (Chapter 6). Root elongation rate decreased with increasing penetrometer resistance and maize was considerably more sensitive than lupin towards increase in these soil physical stresses. The effects of soil mechanical impedance dominated any improvement in root-soil contact. The averaged length of the root elongation zone (estimated from the distance between root hair zone and root tip) was linearly related to elongation rates. This is a possible method for estimating root elongation rates in situ. To manipulate root-soil contact in loosely packed aggregates, seedlings were grown at various matric potentials in soils of different aggregate sizes (4—2 mm, 2-1 mm, 1- 0.5 mm and <0.5 mm). The finer the aggregates were the faster the roots elongated, they also had better root-soil contact (72-79 % at <0.5 mm and 23-25 % at 4 -2 mm). A method was developed to investigate the role of liquid and solid contact with roots. Roots were exposed in different portions to the mist produced in an aeroponic system. In another experiment roots were placed above a water surface and supplied at different parts with water through cotton wool. Different portions of the total surface of the root were in contact with liquid or solid phase. Root and shoot elongation were not significantly affected by the portion of root surface in contact with water or solid phase. A good root-particle contact can can improve plant growth when water availability is limiting growth but the effects of greater contact area are dependant on matric potential, plant species, and soil strength.