Document Type

Thesis - Open Access

Award Date

1987

Degree Name

Master of Science (MS)

Department

Agronomy

First Advisor

D. G. Kenefick

Abstract

A study was conducted in South Dakota to examine the affects of weather on growth and production of agronomic crops. Over a 17-year period of climatic variables were collected on a daily basis and put into weekly means values. It was reported that a frequent cause of loss for winter cereals was in early spring, when the conditions of extreme fluctuations of temperature and the rehydration state of the tissue affected survival. Osmotic adjustment is one metabolically controlled process that is compatible with the timeframe of weather change during this period which might ameliorate the adverse affects of excess free water thereby avoiding the subsequent hazards of temperature fluctuations. Therefore it was postulated that osmotic adjustment may play a role in freeze survival during this period. For the purpose of this study, osmotic adjustment is defined as an accumulation of osmotically active solutes in plant cells resulting in a lower osmotic potential. The effect is to maintain or create a favorable water potential gradient to induce a flux of water from the soil to the plant. Under water deficient conditions, osmotic adjustment enables plants to extend the period of positive cell turgor, and thus physiological functions, down to lower water potentials than normal. The relationship between turgor pressure, cell wall elasticity, and wall plasticity involving cell extension and stress inhibited growth are entwined in the understanding of plant-water requirements. The most common approach to measuring cell wall elasticity has been the mathematical calculation of the bulk elastic modulus. Sucrose is a major translocatable source of carbon in plants. Cell wall associated invertase hydrolyzes sucrose in the apoplast, providing hexoses which can be utilized for energy and to meet other carbon requirements for expanding cells. A direct relationship between invertase activity and osmotic adjustment during drought has not been established. However, abscisic acid which has been found to enter the apoplast and increase in response to drought stress, has been shown to stimulate invertase activity. If in fact sucrose is being imported to young tissue to aid in osmotic adjustment and sustain viability and growth of cells, then one might expect invertase to remain relatively active during drought. The objectives of this study were: 1) to determine the degree of osmotic adjustment and cell wall elasticity in winter wheat, 2) to measure the activity of cell-wall associated glycosidases and invertase during short-term drought stress, 3) to compare enzyme assays with P-V data and examine possible biological relationships that account for osmotic adjustment and/or physical changes in cell wall properties, and 4) to determine if osmotic adjustment occurs as a result of cold acclimation in winter wheat.

Library of Congress Subject Headings

Wheat -- Cytology

Wheat -- Drought resistance

Plant cells and tissues

South Dakota State University Theses

Format

application/pdf

Number of Pages

60

Publisher

South Dakota State University

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