Effects of NO on some physiological characteristics in three species of citrus in water deficit condition

Most plants encounter with different environmental stresses during their life cycle. Water deficit is one of the stresses that negatively affect the growth and yield of many agricultural crops such as members of citrus family. Higher plants developed several physiological and biochemical adaptation systems that give them a chance to survive and let them to escape from water deficit stress. In this research the effect of Nitric Oxide, as a stress modulator, on citrus plants was investigated. A trial was conducted as factorial with randomized complete blocks design in three replications on three species of citrus including Poncirus, Swingle citrumelo and Carrizo citrange. There were also drought stress treatments in three levels (FC, 30% FC and 60% FC) and Sodium nitroprusside treatments, as a NO releasing compound, in three levels (0, 0.5 and 1 mM). Some physiological factors such as chlorophyll fluorescence, stomatal conductance, leaf water potential and leaf relative water content were measured. Also, some biochemical factors such as DPPH and the contents of phenols and malondialdehyde were investigated. The results showed that drought stress, decreased leaf water potential, stomatal conductance, relative water content and Fv/Fm significantly. Some biochemical factors such as DPPH, phenols and malondialdehyde activity increased during drought stress. Application of sodium nitroprusside, modulated the destructive effects of drought stress specially with the concentration of 1 mM.