Effects of salicylic acid application on germination, growth and development of rough lemon (Citrus jambhiri Lush.) under salt stress

Rough lemon (Citrus jambhiri Lush.) – RL, is used as a rootstock for citrus plants in saline conditions. NaCl causes an osmotic stress on plants mainly preventing the water uptake by the roots and thus reducing the plant growth. The objective of this study was to determine the effects of salicylic acid (SA) on germination of seeds and the growth and development of seedlings of RL rootstock under salt stress. For seed germination, a study was conducted in a completely randomized design in a 4 × 4 factorial scheme (SA at 0.00, 0.25, 0.50, or 1.00 mM and NaCl at 0, 50, 100, or 200 mM) with 4 repetitions, totaling 64 plots, of 25 seeds per plot. RL seeds were incubated in SA solutions for 24 h. Then, they were treated with NaCl-containing water in Petri dishes and incubated in the growth chamber at 25°C. For greenhouse experiment, a study was conducted in a randomized complete block in a 4 × 4 factorial scheme (SA at 0.0, 0.5, 1.0, or 2.0 mM and NaCl at 0, 50, 100, or 150 mM) with 3 repetitions, totaling 48 plots, of 2 plants per plot. Some morphological and physiological characteristics were determined. While germination time was extended, germination ratio and radicle extension were decreased in seeds under salt stress compared to control. Moreover, in these conditions the leaf membrane permeability and leaf falling were increased. In turn, plant height, diameter, root and shoot dry weight, leaf relative water content, and leaf chlorophyll were decreased in seedlings. Salt stress had negatively affected seed germination from 97.5% in control to 23.5% in 200 mM NaCl. However, SA treatments significantly decreased plant height to 67.8 cm in 2.0 mM compared to 80.1 cm in control in RL rootstock.