Effects of foliar application of salicylic acid on pigments, photosynthesis, ion leakage, compatible osmolytes and antioxidant enzymes of rapeseed (Brassica napus L.) under chilling stress

Chilling stress inhibits yield of rapeseed. Salicylic acid (SA) can improve plants’ resistance to chilling through modification of many physiological mechanisms. In the present study, foliar of SA was investigated on some physiological characteristics of rapeseed under chilling stress in farm. Treatments included sowing date (conventional date, late September, and late 15-day delay, which represents chilling stress) and SA spraying including no spraying, 0, 100, 200, 300, and 400 µM. Findings revealed that conventional sowing date + 100 µM SA resulted in the maximum chlorophyll, anthocyanins, and proline contents while late sowing date+ 100 µM SA resulted in the maximum flavonoids and soluble sugar. The highest catalase activities were recorded for the plants treated with 100 and 400 µM SA, but delayed sowing + 200 µM SA led to the highest activity of superoxide dismutase. Non-application of SA + conventional date showed the highest ion leakage. Applying low concentration of SA to the rapeseed plants sown in the favorable (conventional) sowing date seems to improve their chlorophyll and anthocyanins contents, and increasing the SA in delayed sowing seems to reduce the adverse effects of chilling stress. In the case of flavonoids and soluble sugars, applying 100 µM SA in the delayed sowing group compensated for the negative effects of low temperature compared with the control, improving the plant’s resistance to this stress. In sum, the most favorable performance in most characteristics of the rapeseed was obtained with conventional sowing date along with applying 100 µM SA.