Document Type

Thesis - University Access Only

Award Date

1995

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Fred Cholick

Abstract

Osmotic adjustment (OA), the active accumulation of solutes within a plant in response to stress, has been linked to drought tolerance in wheat and other plant species. Osmotic adjustment is generally measured on fully expanded plant tissues, experimentally requiring significant time and laboratory space for growing plant material. To circumvent this problem, a coleoptile and seedling root evaluation technique was developed by researchers in Australia. Researchers found that seedling growth measurements under conditions of applied water deficit were highly correlated with OA of adult plant material. The current work utilizes this technique to examine the variation present among spring wheat cultivars adapted to the Northern Great Plains. Sixteen adapted cultivars and two cultivars of known OA were examined in a series of three experiments, which varied in the method of applying the water deficit to the seedlings. Various measurements were taken, including coleoptile and root length and growth and water relations, including solute, water and pressure potentials (ψS , ψW, and ψP) and relative water content (RWC). Study 1 involved the application of water stress by the addition of polyethylene glycol (PEG) osmoticum to the roots of growing seedlings, producing a water stress of -0.62 MPa. Significant differences in coleoptile growth and water relations were observed. The known OA cultivars differentiated in manner consistent with previous studies, confirming the procedures. Cultivars differentiating into a high statistical group for coleoptile growth under high water deficit included Guard, Stoa, and Kite. Alex and 2375 also ranked highly. These results were generally consistent with measurements of ψS under water deficit, where Guard, Stoa, and 2375 were in the high group. In Study 2, seedlings were exposed to water deficit from the beginning of germination. Root growth was widely variable and inconsistent. Coleoptile growth, although somewhat variable, did show that the cultivars differentiated in a manner similar to Study 1, with additional cultivars in the high ranking group. Study 3 involved identical procedures to Study 1, with the exception that water deficit was applied through evaporative drying. The cultivars again differentiated on the basis of coleoptile and root growth as well as for water relations. Cultivar ranking for growth under high water deficit generally corresponded with results of Study 1. In conclusion, significant differences among the cultivars were seen for growth and water relations, indicating that genetic variability is present for these traits. The cultivars Guard, Stoa, and 2375 were consistently near the top of the growth measurements, whereas the cultivars Sharp, Leif, Vance, Bergen, and Chris were consistently lower in the rankings. The results of Studies 1 and 3 show that the method of applying water stress did not significantly affect results. Provided accurate measurements can be taken, selection of cultivars for potential OA and drought tolerance using these methods appears possible.

Library of Congress Subject Headings

Wheat -- Drought tolerance
Wheat -- Effect of stress on

Format

application/pdf

Publisher

South Dakota State University

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Rights Statement

In Copyright