OSMOTIC ADJUSTMENT OF SUGAR-BEETS IN RESPONSE TO SOIL-SALINITY AND ITS INFLUENCE ON STOMATAL CONDUCTANCE, GROWTH AND YIELD

Sugar beets were grown in tanks filled with loam and clay, and were ir rigated with waters of three different levels of salinity. Osmotic adj ustment was determined by analyzing the pressure volume curves at thre e growth stages. Sugar beets showed osmotic adjustment in two ways: wi th their phenological development and towards salinity, Owing to the l atter adjustment sugar beets are able to maintain the turgor potential at the same value for lower values of the leaf water potential, to ma intain stomatal conductance and photosynthesis and finally their produ ction under severe water stress. Salinity affected the pre-dawn leaf w ater potential, stomatal conductance and evapotranspiration on both so ils, but leaf area and yield only on loam. Soil texture affected stoma tal conductance, evapotranspiration, leaf area and yield. As the latte r was about 35% lower on clay, whereas the evapotranspiration decrease d 10 to 15%, the water use efficiency was about 25% lower on clay comp ared with loam. (C) 1997 Elsevier Science B.V.