Journal of Plant Process and Function

In order to investigate the effect of different levels of water deficit and foliar application of humic acid on the physiological characteristics of lima bean, a field experiment was arranged as split-split plot based on randomized complete block design with three replications in the research station of Shahrekord University in 2014. The main plot included four levels of drought stress (50, 70, 90 and 110 mm evaporation from pan class A) and sub plots included four levels of humic acid (0, 1, 3 and 6 lit/ha). In this experiment the traits of Chlorophyll a, chlorophyll b, carotenoids, membrane stability, relative water content of leaves, proline and soluble sugars were evaluated. The results showed that water stress caused significant decrease in all measure traits. Humic acid also significantly increased them. The interaction of water stress and application of humic acid on the carotenoids and proline were significantly affected, but had no effects on other traits. Foliar application of humic acid under drought stress conditions increased concentration of osmo-regulation including soluble sugars and proline and thus maintain osmotic pressure in cells, resulted the plant to resistant in drought conditions.