Effect of water stress on growth, yield and eco-physiological responses offour tomato (Lycopersicon esculentum Mill.) cultivars

The effect of water stress on the growth, yield, and various morphological characteristics related to yield and eco- physiological responses of tomato was studied in two drought- tolerant cultivars, 'TM 0126' (TM) and 'VF- 13 4-1-2' (VF) and two drought- sensitive ones,'Kyokko' (KK) and 'Ratan' (RT). Water stress decreased yield, flower number, fruit set percentage and dry matter production in all cultivars, but the reduction was greater in drough t- sensitive cultivars than in tolerant ones. Photosynthetic rate (Pr), tra nspiration rate (Tr), leaf water potential (psi(w)), and water use efficien cy (WUE) were reduced, and leaf temperature (Tl) and stomatal resistance (r (s)) were increased by water stress in all cultivars. The reduction of Pr, Tr, psi(w) and WUE, however, was less pronounced in tolerant cultivars than in sensitive ones, whereas the increase of TI and r(s) was more conspicuou s in tolerant cultivars than in sensitive ones. After re- watering, all the se eco -physiological responses returned to near normal state, but the reco very was more rapid and complete in tolerant cultivars than in sensitive on es. The better performances of tolerant cultivars under water stress and re covery after re- watering are attributed to the ability of plants to mainta in a better water status and minimize the reduction of photosynthesis.