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Because plants show a wide range of variation in growth in the presence of excessive concentrations of soluble salts in the soil, this study was undertaken to determine the effects of various concentrations of NaCL and Na2SO4 on the growth and development of Hordeum jubatum, Agropyron trachycaulum, and the natural hybrid of these two plants, Elymus macounii.

Stand losses in temperate grasses after summer defoliation of tall canopies inspired an investigation of microenvironmental and plant responses in tall fescue. Microenvironment and regrowth of tall fescue in response to mowing managements and nitrogen rates in spring that created different canopy structures was studied. In early spring, 50 and 160 kg/ha of N were applied. Mowing managements were: clipping at 4 or 8 cm biweekly, monthly, and in late June. In late June all 6 treatments were mowed to prescribed stubble heights with a seventh unmowed check. Canopy light regimes, leaf area index, and regrowth of tillers were monitored along with soil, fair, and shoot temperatures in stubbles after the June harvest. Mowing more frequently in spring decreased canopy yields of the June harvest, but increased leaf area (LAI) of stubbles as compared to spring-accumulated canopies. High nitrogen decreased specific leaf weights (SLW) in stubble leaves and increased LAI except in spring-accumulated canopies. Increased LAI decreased light penetration and canopy temperatures. Temperatures were highest in harvested spring-accumulated stubbles with a shift of 4-10 C between unharvested and harvested stands while radiation penetration into the stubble increased from 5 to 75% of total. Some large stand losses occurred in lodged portions of harvested Spring-accumulated plots. Generally, regrowth yields were not affected by prior clipping managements. Concentration of TNC was uniformly high with all treatments. / Ph. D.

A grass phytoremediation field study was initiated in July 1997 at the site of a former railroad tie facility that used creosote for tie preservation. The site is contaminated with polycyclic aromatic hydrocarbons (PAHs). A test matrix consisting of 36 planted (clover, fescue and rye grasses) and unplanted cells was established. The focus of the study was to evaluate PAH remediation in fertilized plots that were unplanted or seeded with clover, fescue or rye. Samples were collected from a depth of 15 to 21 cm, and the six most prevalent PAHs, acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene and chrysene were quantified. Data from four sampling periods, t=0, 9, 12 and 17 months is presented. At t=9 months, substantial loss of the five lowest molecular weight (LMW) PAHs had occurred, and the loss was attributed to natural attenuation. During the first 9 months, below average precipitation at the site delayed grass root development. Between t=9 and 12 months, above average precipitation was recorded and this appeared to accelerate chrysene removal rates in both the unplanted and planted cells; however, the rate was higher rate in the planted cells. Similarly, fluoranthene and pyrene degradation seemed to be enhanced in the fescue and rye cells. Over the last 8 months of the study, acenaphthene, fluorene and phenanthrene concentrations approached constant, minimum levels suggesting additional removal will be limited. PAH compounds with higher solubility correlated to decreased constituent soil concentrations. Additional sampling was initiated at t=17 months to compare PAH concentrations with depth. This was done because the observed root mass changed significantly with depth. Samples were taken at two additional depths 10 to 15 and 32 to 38 cm. Increased removal of fluoranthene and pyrene was observed in the uppermost zone, suggesting a role for plants in remediation of these 4 ringed PAHs. / Master of Science

Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 2000. / Thesis submitted in fulfilment of the requirement for the degree of Doctor of Philosophy, Centre For Horticulture and Plant Sciences, University of Western Sydney, 2000. Bibliography : leaves 215-231.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references.

Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Much has been written about the effects of soil salinity on plant growth. Its devastating effects have already been reported 2000 years BC. In the 21· century an alarming 80 million hectares of cultivated land area are affected by salt (Munns, 2002a) and represent a growing threat to agriculture. Salt tolerance is a complex trait moderately expressed in only a few plant genotypes (Ruiz, 2001). An attempt to transfer salt tolerance genes from the wild grass, Thinopyrum distichum, to triticale and éommon wheat was initiated by Marais and Marais (2003). A study of Th. distichum x rye hybrids enabled the authors to identify chromosomes 2Jld , 3Jld , 4Jld and SJld as being involved in the determination of salt tolerance. Indirect (yet unconfirmed) evidence suggested that 7Jld might also have a role. A programme aiming to transfer regions of the critical chromosomes to homoeologous triticale chromosomes, which relies heavily on the use of molecular markers, was launched. While an RFLP marker is available for each of the Thinopyrum chromosomes, these are not suited for the screening of large numbers of segregates. This study therefore represents an attempt to convert the RFLP markers into less time consuming and cost-effective SCAR markers. The published DNA sequences of the RFLP probes in question were used as templates to design PCR primers. The PCR reactions were optimised using DNA of Th. distichum, rye and their FI hybrid. When Thinopyrum specific amplification products were obtained, the primers were also tested on a panel of genotypes with and without the target chromosomes. Seemingly polymorphic bands were confirmed by Southern blotting and hybridisation with the corresponding RFLP probes. The primers were also tested on a panel of genotypes that included 'Rex' triticale to ensure that they would also detect a difference in a triticale genetic background during transfer. Polymorphic bands were then isolated and sequenced to further refine the markers. In certain eases, sequences of the same fragment amplified in triticale ('Rex') and Thinopyrum were aligned in an attempt to design more specific markers. Using this approach, it was possible to develop chromosome specific SCARs for Thinopyrum chromosomes 3Jld and 7J2 d . Three and one set(s) of PCR markers, respectively, have been developed and can be used to unequivocally detect the Thinopyrum chromosomes involved in salt tolerance against a triticale background. A SCAR marker was also found for chromosome 6J. Thus, an attempt was made to convert thirteen RFLP probes to SCAR markers. Only three were successfully converted. The main reason for the low success rate is the syntenic relationships between the genomes of the different cereals that made it an arduous- task to find discriminating primer sets. Based on the results obtained, an adapted procedure is suggested for future attempts to develop chromosome specific markers utilizing published sequence information that was obtained for a different species. / AFRIKAANSE OPSOMMING: Baie is al geskryf oor die uitwerking van grond versouting op plantproduksie. Die vernietigende gevolge van versouting is alreeds 2000 jaar VC gerapporteer. In die 21* eeu is 'n geraamde 80 miljoen hektaar (Munns, 2002a) bewerkte land-area sout-geaffekteerd. Die ontstellende verwikkelinge verteenwoordig 'n groeiende bedreiging vir die landbou. Soutverdraagsaamheid is 'n komplekse kenmerk en slegs enkele plantgenotipes met matige verdraagsaamheid kon nog ontwikkel word (Ruiz, 2001). 'n Poging om soutverdraagsaamheidsgene vanaf die wilde gras, Thinopyrum distichum, na triticale en gewone koring oor te dra, is deur Marais en Marais (2003) geïnisieer. 'n Studie van Th. distichum x rog hibriede het die skrywers in staat gestelom chromosome (2Jld, 3Jld, 4Jld en SJld) wat bydra to soutverdraagsaamheid te identifiseer. Indirekte (maar onbevestigde) aanduidings is gevind dat 7J1dook' n rol mag speel. 'n Program is daarna geloods om segmente van chromosome na homoeoloë triticale chromosome oor te dra, 'n onderneming wat swaar steun op die gebruik van molekulêre merkers. Alhoewel daar'n RFLP merker beskikbaar is vir elk van die Thinopyrum chromosome, is hierdie merkers nie geskik vir die sifting van groot getalle segregate nie. Hierdie studie verteenwoordig 'n poging om die RFLP merkers om te skakel na 'n minder tydrowende en meer koste-effektiewe SCAR merkers. Die gepubliseerde DNS-volgordes van die betrokke RFLP peilers is as templaat gebruik om PKR inleiers te ontwerp. Die PKR reaksies is geoptimiseer deur gebruik te maak van DNS van Th. distichum. rog en hulle FI hibried. In gevalle waar Thinopyrum spesifieke amplifikasie produkte verkry is, is die inleiers ook getoets op 'n paneel van genotipes met en sonder die teikenchromosoom. Skynbare polimorfiese bande is bevestig deur 'n 'Southern' klad te maak en te hibridiseer met die tersaaklike RFLP peiler. Die inleiers is ook getoets op 'n paneel van genotipes waarby 'Rex' triticale ingesluit was om te verseker dat dit ook verskille in 'n triticale genetiese agtergrond opspoor (nodig tydens oordrag). Polimorfiese bande is verder verfyn. Dit is geïsoleer en die DNS-volgorde daarvan is bepaal. Tn sekere gevalle is ooreenstemmende fragmente geamplifiseer in triticale ('Rex') en Thinopyrum. Die volgordes is dan bepaal en met mekaar vergelyk in 'n poging om meer spesifieke merkers te ontwerp. Met die gebruik van hierdie benadering was dit moontlik om chromosoom-spesifieke SCAR-merkers vir die Thinopyrum chromosome 3Jld en 7J2d te ontwikkel. Drie en een stel(le) PKR merkers is onderskeidelik ontwikkel en kan gebruik word om ondubbelsinnig te bepaal of die betrokke Thinopyrum chromosoom segregeer in 'n triticale kruising. 'n SCAR merker is ook gevind vir chromosoom 6J. Dus, daar is probeer om dertien RFLP peilers na SCAR merkers om te skakel. Slegs drie van die pogings was suksesvol. Die hoofrede vir die lae sukseskoers is die hoë graad van sintenie tussen die genome van die verskillende grane wat dit 'n moeilike taak gemaak het om diskriminerende inleierstelle te ontwerp. Op grond van die resultate word 'n ietwat gewysigde prosedure vir die toekomstige pogings om chromosoom-spesifieke merkers te ontwerp met gebruik van gepubliseerde volgorde inligting vanaf' n ander spesie, voorgestel.

The success of C₄ plants lies in their ability to concentrate CO₂ at the site of Rubisco thereby conferring greater efficiencies of light, water and nitrogen. Such characteristics should advantage C₄ plants in arid, hot environments. However, not all C₄ subtypes are drought tolerant. The relative abundance of NADP-ME species declines with increasing aridity. Furthermore, selected species have been demonstrated as being susceptible to severe drought showing metabolic limitations of photosynthesis. However there is a lack of phylogenetic control with many of these studies. The aims of this study were to determine whether the NADP-ME subtype was inherently susceptible to drought by comparing six closely related C₃ and C₄ (NADP-ME) Panicoid grasses. Gas exchange measurements were made during a natural rainless period and a controlled drought / rewatering event. Prior to water stress, the C₄ species had higher assimilation rates (A), and water use efficiencies (WUE[subscript leaf]) than the C₃ species, while transpiration rates (E) and stomatal conductances (g[subscript s]) were similar. At low soil water content, the C₃ species reduced gs by a greater extent than the C₄ species, which maintained higher E during the driest periods. The C₄ species showed proportionally greater reductions in A than the C₃ species and hence lost their WUE[subscript leaf] and photosynthetic advantage. CO₂ response curves showed that metabolic limitation was responsible for a greater decrease in A in the C₄ type than the C₃ type during progressive drought. Upon re-watering, photosynthetic recovery was quicker in the C species than the C₄ species. Results from whole plant measurements showed that the C₄ type had a significant whole plant water use efficiency advantage over the C₃ type under well-watered conditions that was lost during severe drought due to a greater loss of leaf area through leaf mortality rather than reductions in plant level transpiration rates. The C₃ type had xylem characteristics that enhanced water-conducting efficiency, but made them vulnerable to drought. This is in contrast to the safer xylem qualities of the C₄ type, which permitted the endurance of more negative leaf water potentials than the C₃ type during low soil water content. Thus, the vulnerability of photosynthesis to severe drought in NADP-ME species potentially explains why NADP-ME species abundance around the world decreases with decreasing rainfall.

"The orientation of this study began with a collection of the grasses of Erath County during their flowering periods. Collections were made in the Spring and Fall of 1950 and 1951 to obtain both vernal and autumnal grasses. Identifications were made from the grass floras previously mentioned and checked against specimens in the herbarium of North Texas State College for verification. In addition, the list was checked by W.A. Turney, Conservationist, United States Department of Agriculture of Dublin, Texas. Finally, the list was compared with that prepared by W.M. Cory for the plant areas of which Erath County is a part. On the basis of the above identifications, a critical study of the vegetative characteristics was made and a key based on these features prepared. The width of the blad and characteristics of the ligule, roots, culms, and sheaths were used to distinguish each of the eighty-six specimens found in the collection area. A drawing was made of the longitudinal section of the juncture of the blade and the sheath of each grass. This diagnostic section includes the collar, ligule, a part of the blade and sheath, and auricles, if present."-- leaf 5.

Typescript (photocopy). / Digitized by Kansas Correctional Industries