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Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1977 / Bibliography : leaves 29-30. / M.S. / M.S. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

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Root growth potential CRGP) is the measure of seedling ability to grow new roots. Loblolly pine (Pinus taeda L.) seedlings from 5 seedlots were raised at two widely separated nurseries (Summerville, SC and New Kent, VA). In Experiment I, RGP was determined during the fall and winter of 1984-85 and 1985-86, and several morphological traits were measured. In Experiment II seedlings from the same seedlots were lifted during February 1985 and 1986 at both nurseries, and cold stored until subsequent outplanting; subsamples of outplanted seedlings were used for RGP determinations. Root growth potential varied significantly by family, nursery, and lift date, and first order interactions were significant. Generally, the RGP of Summerville raised seedlings was higher than that of New Kent raised seedlings. RGP was not strongly correlated with common measures of shoot morphology, but RGP was consistently well correlated with lateral root dry weight. In Experiment II, RGP varied significantly by family, nursery, and storage duration. The family x nursery effect was the only significant interaction. Summerville raised seedlings had higher RGP on each planting date. During each year RGP declined rapidly in storage. First year survival was significantly correlated with RGP (r = .52, p < .001). Height increment and RGP were also strongly correlated (r = .80, p < .001). These relationships and their implications for nursery management were discussed. / M.S.

The interactions between soil physical properties, particularly soil structure and bulk density, and the rooting of four herbaceous crops grown for biomass on three common Piedmont soil series were examined. The effect of these crops on soil properties over time was also studied. The rooting of the biomass crops studied seemed to be affected by soil physical factors on two of the three soils. Even though bulk density on all three soils (Appling, Cecil, and Davidson) appeared high enough to drastically limit rooting, such limitations were found only at the Appling sites and, to a much lesser extent, at the Cecil sites. Well-developed soil structure seemed to be instrumental in the success of the biomass crops on these dense Piedmont soils. All of the species studied had vigorous root systems in well-structured, high-density soils. Weeping lovegrass (<i>Erogrostis cuxvula</i>) was particularly insensitive to high bulk densities. The root systems of switchgrass (<i>Panicum virgatum</i>), birdsfoot trefoil (<i>Lotus corniculatus</i>), and sericea lespedeza (<i>Lespedeza cuneata</i>) were all heavily influenced by the high densities of the nearly structureless Appling soils; but lovegrass roots were quite prolific there. For this reason lovegrass should be considered first for biomass production on similar marginal soils. All soils had higher organic matter contents after four years of biomass production. Soil nutrient concentrations, particularly soil K, were also higher, especially under switchgrass. Soil Ca and Mg contents were higher under the two legumes than under the two grasses. / Master of Science

This thesis presents research associated to phenotyping of plants by applying informatics techniques which includes databases, web technologies, image processing and feature measurements of 2D and 3D images. The thesis presents two enabling bioinformatics tools related by a shared set of research objectives and distinct by the nature of their applications. The first project called ClearedLeavesDB, is a common platform for plant biologists to share data and metadata about cleared leaf images. This project resulted in an online interactive database of cleared leaf images. The second project called Digital Imaging of Root Traits (DIRT), is an application to store, manage, share and process root images as well as analyze root image traits with respect to different experiments. This application is deployed on iPlant's cyber-infrastructure and currently supports management of 2D root images and high-throughput processing and structural descriptor/trait estimation from root images. The application enables storage, management and sharing heterogeneous image data and metadata including dynamic environmental and descriptor data. In the final part of the thesis, I describe ongoing challenges in developing new methods to measure global and local descriptors from reconstructed 3D root images.

Call number: LD2668 .T4 1962 F64

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This study aimed to assess the contribution of anaplerotic C prOVISIOn VIa phosphoenolpyruvate carboxylase (pEPc, EC 4.1.1.31), during Pi stress in the root and nodule components of Lupinus angustifolius. The role of PEPc in DIC metabolism in roots and nodules of phosphate-starved plants was studied. The symbioses involving leguminous plants and species of Rhizobium and Bradyrhizobium bacteria form an integral part of effective management ofN in the environment. In agricultural settings, roughly 80% of this biologically fixed N2 comes from this type of symbiotic relationship. Nitrogen-fixing bacteria in concert with legumes fix atmospheric nitrogen, which is then available to the infected plant. Worldwide, legumes are grown on approximately 250 Mha and they fix about 90 Tg (90 billion tons) of N, per year. The overall stoichiometry for nitrogen assimilation in the nodule requires one molecule of oxaloacetate to be converted to one molecule of asparagine per dinitrogen molecule fixed. One possible source for the required oxaloacetate is the reaction catalysed by PEPc. The reaction catalysed by PEPc is a major source of anaplerotic carbon for the plant and it is expected that this reaction will be even more important to plants under Pi stress, as the reaction is not ATP-dependent. Seeds of Lupinus angustifolius (cv. Wong a) were inoculated with Rhizobium sp. (Lupinus) bacteria and grown in hydroponic culture. Tanks were supplied with either 2 11MP04 (LP) or 2 mM P04 (HP) and air containing 360 ppm CO2. Roots experienced pronounced P stress with a greater decline in Pi, compared to nodules. Under P stress, PEPc activities increased in roots but not in nodules and these changes were not related to the expression of the enzyme. Root and nodular PEPc were not regulated by expression, but possibly by posttranslational control. LP roots also synthesised more pyruvate from malate than LP nodules. The role of pyruvate accumulation under Pi stress, was further highlighted by the metabolism of PEP via both the pyruvate kinase (PK, Ee 2.7.1.40) and PEPc routes. The enhanced PK activities supported these high pyruvate levels. The results show unequivocally that nodules do not experience P stress to the same extent as roots. Implications of the findings are that nodules require low P to function normally. Maintenance of phosphate levels in nodules may be at the expense of host. It can be suggested that when nodules are P-starved they can become aggressive scavengers for available P and even out-compete roots. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die bydrae van anaplerotiese koolstof-voorsiening via fosfo-enolpirovaatkarboksilase (pEPc, EC 4.1.1.31), tydens fosfaatstremming in die wortels en wortelknoppies van Lupinus angustifolius te bepaal. Die rol van PEPc in die metabolisme van opgeloste anorganiese koolstofdioksied in fosfaat-beperkte wortels en wortelknoppies is ondersoek. Die simbiose tussen peulplante en spesies van Rhizobium en Bradyrhizobium bakterieë vorm 'n integrale deel van die doeltreffende bestuur van stikstof in die omgewing. In die landbou word ongever 80 %van biologies-gefikseerde stikstof deur hierde simbiotiese verhouding geproduseer. Stikstotbindende bakterieë, in simbiose met peulplante, fikseer atmosferiese stikstof, wat dan beskikbaar is vir die geïnfekteerde plant. Wêreldwyd fikseer peulplante ongeveer 90 biljoen ton stikstof per jaar. Die algehele stoïgiometrie vir stikstof-fiksering in wortelknoppies vereis dat een molekule oksaalsuur na een molekule asparagien omgesit word per stikstofmolekule wat gefikseer word. Een moontlike bron vir die benodigde oksaalsuur is die reaksie wat deur PEPc gekataliseer word. Die reaksie wat deur PEPc gekataliseer word is 'n belangrike bron van anaplerotiese koolstof vir die plant en dit word vermoed dat hierdie reaksie van nog groter belang sal wees vir plante onder fosfaatstremming, omdat die reaksie nie ATP-afhanklik is nie. Sade van Lupinus angustifolius (cv. Wonga) is geïnokuleer met Rhizobium sp. (Lupinus) bakterieë en gekweek in waterkultuur. Tenke is voorsien met óf 2 !lM P04 (LP), óf 2 mM P04 (HP) en lug wat 360 ppm CO2 bevat het. Wortels het skerp fosfaatstremming ervaar, met 'n groter afname in Pi, vergelykbaar met wortelknoppies. Tydens fosfaatstremming het die aktiwiteit van PEPc toegeneem in wortels, maar nie in wortelknoppies nie en hierdie veranderinge was nie verwant aan die uitdrukking van die ensiem nie. PEPc van wortels en wortelknoppies is nie gereguleer deur uitdrukking nie, maar moontlik deur post-translasie kontrole. Wortels onder 'n lae-fosfaat voorsiening het ook meer pirodruiwesuur vanaf malaat gesintetiseer as wortelknoppies. Die rol van pirodruiwesuur-akkumulering tydens fosfaatstremming is verder beklemtoon deur die metabolisme van PEP via beide die pirovaatkinase- (PK, EC 2.7.1.40) en PEPc- roetes. Die verhoogde PK-aktiwiteite verklaar hierdie hoër vlakke van pirodruiwesuur. Die resultate toon ondubbelsinnig dat wortelknoppies me tot dieselfde mate fosfaatstremming ervaar as wortels nie. Dit impliseer dat wortelknoppies min fosfaat benodig om normal te funksioneer. Handhawing van fosfaatvlakke in wortelknoppies mag ten koste van die wortel wees. Dit is moontlik dat, wanneer wortelknoppies fosfaatbeperk is, hulle aggressiewe opruimers word vir beskikbare fosfaat en selfs beter funksioneer as die wortels.

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