Gas exchange characteristics and water relations in some elite okra cultivars under water deficit

Thirty-days-old plants of two cultivars of okra (Hibiscus esculentus L.), Sabzpari and Chinese-red, were subjected for 30 d to two water regimes (100 and 60 % field capacity). Leaf water potential and osmotic potential of both lines decreased significantly with the imposition of drought. Both the leaf pressure potential and osmotic adjustment were much lower in Chinese-red than those in Sabzpari. Chlorophyll (Chl) b content increased, whereas Chl a content remained unchanged and thus Chl a/b ratios were reduced in both lines. Drought stress also caused a significant reduction in net photosynthetic rate (P-N), transpiration rate (E), stomatal conductance (g(s)), and water use efficiency (WUE) especially in cv. Sabzpari. The lines did not differ in intrinsic WUE (P-N/g(s)) or intercellular/ambient CO2 ratio. Overall, the growth of two okra cultivars was positively correlated with P-N, but not with g(s) or P-N/E, and negatively correlated with osmotic adjustment.