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Response of Wheat to Combined High Temperature and Osmotic Stress During Maturation. II. Plant Water Relations

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Author(s): Nazeer Hussain Shah | Gary M. Paulsen

Journal: Pakistan Journal of Biological Sciences
ISSN 1028-8880

Volume: 3;
Issue: 10;
Start page: 1639;
Date: 2000;
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ABSTRACT
High temperature and drought affect plant processes individually and may interact to alter water relations. Our objectives were to ascertain the effect of high temperature and osmotic stress and to identify interactions between them on water relation of wheat (Triticum aestivum L. cv. Len). Plants that were grown uniformly until anthesis were subjected to 15/10, 25/20 or 35/30 °C and -0.01 or 0.41 Mpa water stress and were sampled weekly until maturity. Relative water content (RWC) of flag leaves remained constant at low temperature and declined quickly at high temperature. Osmotic stress decreased RWC slowly at low temperature and rapidly at high temperature as plants matured. Water potential and osmotic potential reacted similarly, staying high at low temperature and falling faster as the temperature increased or osmotic stress impinged. Turgor potential was sometimes higher under 15/10 °C with osmotic stress than under other regimes, but varied lesser than other pressure components. Cumulative water use ranked 25/20 > 15/10 > 35/30 °C without osmotic stress > 15/10 °C = 25/20 °C = 35/30 °C with osmotic stress. Water use efficiency for grain mass was reduced by high temperature and increased by osmotic stress. Results demonstrated that high temperature and osmotic stress interact by complementary effect on water relations and beneficial effects of low temperature on osmotic adjustment to stress.
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