Desiccation tolerance of Photosystem II in dryland fruit crops

Dryland fruit crops are highly prone to stresses caused by depleting soil moisture coupled with high ambient temperatures, particularly during summers. This is more conspicuous and seldom deleterious during droughts, which recur periodically. However, some of the crops sustain and recover their growth after the drought. Since desiccation of leaf is one of the consequences of depleting soil moisture and high temperature, we predicted that those crops that can maintain their photosynthetic efficiency during such stresses could outperform others. We hypothesised that the variation exists in the sensitivity of Photo system II (PS-II) component of the photosynthesis system among the dry land fruit crops. A series of experiments were conducted for assessing the desiccation responses of leaves of six fruit crops by employing chlorophyll fluorescence imaging, which reveals PS-II efficiency. As expected, there was a drastic reduction in the maximum quantum efficiency of PS-II (QYmax) of leaves of all the fruit crops with the decrease in tissue water content. However, there were significant differences among the crops in their responses to the desiccation of leaves. The PS-II tolerance to tissue dehydration observed in karonda (Carissa carandas L) and sweet orange (Citrus sinensis),was higher than that of mango (Mangifera indica L) and grape (Vitis vinifera L). This study reveals the method to assess the sensitivity of fruit crops to desiccation, which can be useful in water management, and in assessing the efficacy of novel chemicals for alleviating abiotic stresses.