Ten grape rootstocks were subjected to moisture and salinity stress in two separate experiments. The influence of these stresses on gas exchange, water relation, and biochemical parameters was monitored at various stages of stress cycle. Both stresses indicated significant changes in the physiological and biochemical parameters studied. Some biochemical constituents increased by several folds in few rootstock cultivars which also recorded increased osmotic potential suggesting their role in osmotic adjustment. Some of the rootstock cultivars such as 110R, 1103P, 99R, Dogridge, and B2/56 recorded increased phenolic compounds under stressed conditions. The same rootstock also recorded increased water use efficiency. The increased accumulation of phenolic compounds in these cultivars may indicate the possible role of phenolic compounds as antioxidants for scavenging the reactive oxygen species generated during abiotic stresses thus maintaining normal physiological and biochemical process in leaves of resistant cultivars. 1. Introduction Water scarcity and soli salinity are the major hurdles for grape cultivation as the majority of the area under grape cultivation is concentrated in the semiarid tropical climate of India. The combined effect of these two abiotic stresses in these regions contributed to a decline in the productivity of own-rooted vineyards. Hence, interest in grape rootstocks has intensified, owing to the problems of salinity and drought. Over dependence on a single rootstock Dogridge necessitated the growers to use other rootstocks as some rootstocks cannot perform well under all soil and climatic conditions. Rootstocks are known to influence physiology and biochemical process of the grafted scion varieties as evidenced by several studies. Hence, it is necessary to study the mechanisms by which rootstocks respond to drought and salinity stresses. Rootstocks have been reported to alter the water status and gas exchange parameters of scion varieties in both potted [1] and field conditions [2]. The most important mechanism is that rootstocks genotypes have a major influence on root density [3] although the distribution of grapevine roots is significantly dependent on both soil characteristics and vine spacing. Salt stress in higher plants is regulated by a number of physiological and biochemical processes. High level of salt causes an imbalance of cellular ions resulting in both ion toxicity and osmotic stress causing a production of active O2 species (AOS) as superoxide, hydrogen peroxides, and hydroxyl radicals [4]. To reduce AOS induced
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