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Leaves of young barley (Hordeum vulgare cv Arivat) seedlings were examined anatomically, physiologically and cytologically to infer the pathway of transpirational water movement and to understand the basis for the selective responsiveness of the growing region to osmotic stress. Vessels with open lumens were found to extend from the intercalary meristem to the expanded blade, and all vessels are present in 5 functional vascular bundles (FVB) which are separated by 20 to 30 closely packed mesophyll cells and 2 to 3 immature vascular bundles (IVB). Heat pulse transport data confirmed the anatomical suggestion that water will move throughout the leaf in open vessels and they showed also that osmotic stress will reduce water transport within 1 min, which is before transpiration is lowered. Water representing about 2 per cent of the total tissue water was obtained by centrifuging cut sections of the growing region at 5 X g against an adsorptive surface. This water is probably xylem plus cell wall water because it is easily removed, its volume is 2X that calculated to be in the vessels, and it exchanges more readily with the water in the nutrient solution than the bulk tissue water. This lack of free exchange indicates apoplastic water is somewhat separated from mesophyll cells, and it is hypothesized that osmotic stress causes sudden growth cessation and initation of metabolic changes because (a) reduced water availability together with ongoing transpiration will cause a sudden reduction in the xylem's water potential, (b) there is a lateral transmission of this reduced water potential through walls of all cells in the growing region, and (c) cells can respond in some way to changes in water potential around them. Most cells in the expanded blade are considered unresponsive to osmotic stress because transpirational water will move predominantly from the 5 FVB through the closest stomata, so only cells closest to those bundles will be altered rapidly by stress.

The ability of different seedbed preparation treatments to enhance seedling establishment of 'Vaughn' sideoats graina (Bouteloua curtipendula (Michx.) Torr.), 'A-130' blue panic (Panicum antidotale Retz.), 'A-68' Lehmann lovegrass (Eragrostis lehmanniana Nees) and 'Cochise' Atherstone lovegrass (Eragrostis lehmanniana Nees X E. tricophera Coss and Dur.) was determined in field and greenhouse experiments. Field experiments compared seed burial and seedling emergence on undisturbed plots with that of plots lightly or heavily trampled by cattle, furrowed with a land imprinter or plowed. Seed burial was nearly always greatest in plots disturbed by these 3 latter treatments compared to undisturbed or light-trampled plots. Summer thunderstorms increased burial on treated and undisturbed plots. These seedbed treatments likewise increased seedling emergence of all species during a moderately-wet summer but not during a dry summer when emergence was limited. Sideoats graina emergence was low all 3 years. Seed burial and emergence of the small-seeded lovegrasses was high in a wet year even on undisturbed plots. Greenhouse experiments were designed to determine effects of seedbed microsites, sowing depth and soil water on emergence, survival and morphology of sideoats graina, blue panic and Cochise lovegrass. Emergence of all species was highest from seeds under gravel, followed by seeds under litter, seeds in cracks and finally seeds on the bare soil surface. Cochise lovegrass had high emergence under gravel for both continuously-wet and drying seedbeds. Cochise lovegrass had greater survival, followed by blue panic and then sideoats graina. All 3 species initiated permanent roots from nodes near the soil surface regardless of sowing depth. Seedlings from deeper-sown seeds had shallower primary roots and less survival than seedlings from shallow-sown seeds. Although seedbed treatments may increase the number of seeds buried and thereby increase seedling emergence when summer storms are frequent, treatments which bury seeds too deep may decrease seedling emergence. Seedbed treatments do not ensure successful emergence in a dry year.

Experiments were conducted to determine if there was a residual effect of the experimental plant growth regulator Ortho XE-1019, (E)-(P-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-l-yl)-l-penten-3-01, remaining in Deltapine 50 and 90 cottonseed obtained at three harvest dates from experiments run at the University of Arizona Marana and Maricopa Agricultural Centers in 1986. Commercial DPL 50 seed were treated with XE-1019 in a second experiment. Several growth characteristics were measured including dry weights after 7 and 12 days. Hypocotyl length was not significantly different between treatments after 12 days of growth, with one exception, nor between dates of harvest for DPL 90 and DPL 50. Other measurements sometimes had statistical differences which were more academic but would be of little consequence in obtaining a satisfactory field stand. A significant reduction of hypocotyl length resulted when seed was directly treated with XE-1019 and would result in poor emergence. Results indicated that the use of XE-1019 as a plant growth regulator on cotton would not have significant residual responses on early seedling growth of Deltapine 90 and Deltapine 50 when the resulting seed are used for planting seed in the next generation.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Bibliography: leaves 186-202. / xvii, 202 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1994

Bibliography: leaves 186-202.

Thesis (Ph. D.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 199-209). Also available on the World Wide Web.

Graduation date: 1991

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