The impact of potassium phosphite on growth parameters and antioxidant activities of sour orange (Citrus aurantium L.) in response to salinity

Salinity stress is among the abiotic stresses that restrict citrus growth. In this regard, the appropriate suitable solutions to improve growth characteristics and antioxidant responses under salt stress conditions can be useful. The present pot research was conducted as a factorial experiment in a completely randomized design with three replications in the greenhouse of the University of Hormozgan during 1401. The used sour orange plants were six-month-old seedlings (height about 60 cm) that were healthy and disease-free. Experimental treatments included water salinity (1.5, 3, 4.5, and 6 dS/m) and potassium phosphite (KPhi((0, 1.5, and 3 g/l). The results revealed that the salinity of 6 dS/m compared to the salinity of 1.5 dS/m led to a decrease in leaf number, stem length and root volume (44.09, 11.4 and 37.5%, respectively) and increased ion leakage and malondialdehyde (9.23 and 41.7%, respectively). Application of potassium phosphite (KPhi( (1.5 g/l) compared to the salinity of 6 dS/m increased leaf number, stem length, root volume and root length (43.5%, 34.4%, 67.2% and 27.3%, respectively). In addition, increased protein content and activity of catalase, superoxide dismutase, phenylalanine ammonialyase, guaiacol peroxidase and ascorbic peroxidase increased (33.9, 94.4, 6.24, 22.8, 73.7 and 94.4%, respectively). Potassium phosphite (KPhi( decreased ion leakage and malondialdehyde (28.6% and 24.13%, respectively). Finally, this study showed that potassium phosphite (KPhi( (1.5 g/l) stimulates the antioxidant system, neutralizes oxygen free radicals, improves growth characteristics and moderates the harmful effects of salinity stress in sour orange seedlings.