A. Danaeifar - Department of Horticultural Science, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Islamic Republic of Iran.
E. Khaleghi - Department of Horticultural Science, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Islamic Republic of Iran.
Sh. Zivdar - Department of Horticultural Science, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Islamic Republic of Iran.
Kh. Mehdikhanlou - Department of Plant Production Engineering and Genetics, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Islamic Republic of Iran.

Citrus is one of the most important fruits whose growth performance and production is significantly affected by environmental stresses. Abiotic stresses, such as salinity and alkaline pH, strikingly limit citrus growth and development. The aim of the present study was to investigate the effect of four NaCl concentrations (۰, ۳۰, ۶۰, ۹۰ mM) and two pH levels (۶.۵ and ۸.۲) on some of morphological, physiological, and biochemical parameters of two citrus rootstocks (Sour orange and Bakraei rootstocks). The experiment was conducted as factorial based on a completely randomized design with four replications, at the Faculty of Agriculture, Shahid Chamran University of Ahvaz, Iran. The results showed that the value of shoot dry weight, fresh and dry weight of roots, and transpiration were significantly decreased in both Bakraei and Sour orange rootstocks when receiving irrigation with ۹۰ mM supplement of salinity at pH= ۸.۲. Proline and carbohydrates of citrus rootstocks were considerably increased by increasing the levels of salinity (۹۰ mM NaCl) and alkaline stress (pH= ۸.۲) in each rootstock, at which condition the photosynthesis rate of Sour orange and Bakraei also declined by ۳۴.۷۷ and ۵۰.۸۰%, respectively. The activity of antioxidant enzymes such as peroxidase, catalase, and superoxide dismutase were increased by ۵۷.۴۲, ۴۲.۱۰, and ۴۵.۸۶% in Sour orange rootstock and ۴۲.۰۴, ۲۶.۷۸, and ۳۷.۹۲% in Bakraei rootstock, respectively. Overall, it can be concluded that the growth performance of Sour orange rootstock is more suitable than Bakraei to tolerate salt-alkali conditions.

Abiotic stress, Antioxidant enzymes, Citrus aurantium, Salinity stress, Sour orange.