Study of physiological and biochemical responses of basil (Ocimum basilicum) to silicon spraying under salinity stress

Salinity stress is one of the environmental stresses and restricts growth and production, the intensification of which in recent years has led to a significant reduction in yield in plants. About 20% of the total irrigated land in Iran (about 33 million hectares) is saline land. In Iran, about 7 million hectares of agricultural land have different degrees of salinity, which is likely to increase due to unfavorable factors such as poor drainage, evapotranspiration and improper use of groundwater resources. The first effects of salinity in plants are osmotic stress. Silicon is the second most abundant mineral compound on Earth, and its positive effects on plant tolerance to environmental stresses have been identified. Silica uptake by plants under salinity stress increases H + -ATPase and H + -Ppase activity in plasma membranes and tonoplasts, resulting in decreased sodium uptake and increased potassium uptake and altered ion division in roots and leaves of Plants. Therefore, current research was conducted to investigate the effects of silicon spraying on physiological traits of basil as an important medicinal and food plant under salinity stress.

This experiment was performed as a factorial in a completely randomized design with 4 replications in potted conditions in Behbahan city of Khuzestan province in 2021 . The first factor was salinity stress (zero and 150 mmol) and the second factor was silicon spraying (zero and 2 g / l), which was considered in accordance with the manufacturer's recommendation. In this experiment, traits such as quantum yield, chlorophyll index measured by SPAD meter, chlorophyll a, chlorophyll b, carotenoids, total chlorophyll, soluble sugar and soluble protein in basil were measured.

Evaluation of the data showed that salinity stress reduced quantum yield, number of chlorophyll meters (SPAD), chlorophyll b, carotenoids, total chlorophyll, soluble sugar and soluble protein. The results of the present study also showed that silicon spraying, especially under salinity stress condition, increased quantum yield, number of chlorophyll meters (SPAD), chlorophyll a, soluble sugar and soluble protein. At the 150 mM salinity stress, the effect of silicon spraying on improving the effects of salinity stress on some traits such as quantumy yield and soluble sugar was more, so that these traits increased by 0.95 and 36.49%, respectively. The interaction of salinity and silicon spraying showed that non-stress irrigation of salinity and silicon spraying increased soluble sugar and soluble basil protein.

The results of this experiment showed the beneficial effects of silicon spraying under salinity stress. The beneficial effects of silicon appear to be more pronounced when the plant is exposed to salinity stress, although this benefit exists under favorable conditions.