An overview of differential response of litchi trees to water stress

Water scarcity is a severe environmental constraint in litchi growth, production and productivity. Drought-induced loss in fruit yield probably exceeds losses from all other causes, since both, the severity and duration of the stress, are critical. These changes are mainly related to altered metabolic functions affecting plant growth. This review entails the effects of drought stress on growth, tree, soil and leaf nutrient status, gas exchange, hormonal balance, fruit yield and quality of litchi. The possible mechanism of the effect of drought in litchi trees on a morphological, physiological and biochemical basis have been elucidated. Drought stress reduces extension growth, disturbs plant water relations, reduced water-use efficiency and negatively impact fruit yield and quality in litchi. Litchi trees response to drought through a variety of physiological and biochemical processes, at cellular and whole-organism levels, thus making it a complex phenomenon. CO₂ assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes thereby affecting photosynthesis. Under drought stress, the production of ROS increases causing damage to biological macromolecules. Litchi trees display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased leaf mass-to-area ratio, partial closure of stomata, increased production of abscisic acid (ABA) and enhanced water uptake with prolific and deep root systems. Various management strategies have been proposed to cope with drought stress in litchi. Light and regular but not excessive irrigation to maintain soil moisture and to improve humidity has been the better known.