effect of severe water stress on some characteristics in citrus seedlings

as regards citrus growing in sub-tropical and tropical regions that often expose drought, in order to investigation of some citrus seedlings response to drought this research was done in factorial experiment based on randomized completely design with three replication under glasshouse conditions. first factor were five citrus rootstocks and second factor included two treatment of irrigation (optimum irrigation and withholding irrigation for six weeks). the results showed that proline, soluble sugars, malondialdehyde and carotenoid in the majority of rootstock increased and total, b and a chlorophylls decreased in drought stress. maximum accumulation of proline was observed in drought stress in backraii rootstock, maximum accumulation of soluble sugars in sour orange and minimum accumulation of proline and soluble sugars in mexican lime. interaction between rootstock and irrigation treatments was not significant. decreasing amount of total chlorophyll, chlorophyll a and b in rough lemon rootstock was more than other rootstocks and decreasing amount of chlorophyll a in sour orange and total chlorophyll and chlorophyll b in macrophylla was minimal. furthermore, increasing amount of carotenoid in sour orange was more than other rootstocks and in mexican lime was least. therefore, sour orange rootstock because of increasement of soluble sugars and carotenoid was the most rootstock tolerant in drought.