Water Relations and Drought Adaptations in Pisum sativum

Abstract

The work reported here concerns the analysis of some aspects of the water relations of the adapted plants, The pressure chamber technique during and after water stress was used and light microscopical observations were made to study the cellular and anatomical adaptations. Pisum sativum plants were used ocr this work as a model system for drought adapted plants. We reported earlier that these plants are able to attain drought adaptation. Important features identified in this study as indicators for drought adaptation in this study are the ability of the plants to: 1) maintain high water potential (-6 to -8 bars) and turgor pressure at water deficit conditions; 2) rapid close stomata under water shortage conditions; 3) accumulate solute during a long recovery period: 4) accumulate K+ in the intercellular space, 5) retain more living stem parenchyma cells under water deficit conditions, and to develop smaller vascular bundles and xylem vessels. Despite the development of these features during adaptation, small changes in internal water balance (both water and osmotic potential) were found to be related to larger changes in membrane properties especially those involved in K+ uptake from the medium. This is in line with our earlier observation that membrane adaptation increased lipophily which could be an important factor for drought resistance.