Priming Of Seeds With NO Donor Sodium Nitroprusside (SNP) Alleviates The Inhibition On Wheat Seed Germination And The Growth Of Wheat Seedlings By Salt Stress

Salinity is one of the major abiotic stressors in the world, which affects the plant growth and crop production. The plants which grow in the saline soil are affected by salt stress in different degrees. Nitric oxide (NO) is a freely diffusible, gaseous compound and an important signal molecule in living organisms. In plants, NO influnences aspects of growth and development, and can affect plant response to stress. NO has two different effects on plants: protection and toxicity. Therefore, the relationship between the concentration of nitric oxide donor sodium nitroprusside (SNP) and the physiological responses of plants under salt stress needs to be further investigated.Priming of seeds with nitric oxide donor sodium nitroprusside (SNP) was used to study effect of exogenous NO on the germination of wheat seeds and the growth of wheat seedlings (Triticum aestivum L. cv. DK961) under salt stress. The results showed that employment of exogenous NO donor (0.02~0.1 mmol/L SNP) in the darkness for 24 h significantly alleviated the growth inhibition of wheat seedlings under salt stress, and 0.06 mmol/L SNP pre-treatment gave rise to the best alleviative effect. 100 mmol/L NaCl treatment significantly suppressed the germination rate,germination index, vigor index and imbibition rate of wheat seeds, while priming of seeds with exogenous NO donor 0.06 mmol/L SNP for 24 h markedly alleviated the decrease of the germination rate,germination index, vigor index and imbibition rate of wheat seeds under salt stress. Interestingly, priming of seeds with 0.06 mmol/L SNP for 24 h significantly alleviated the decrease of theβ-amylase activity but almost did not affect theα-amylase activity under salt stress. Presoaking seeds with SNP slightly increased theα-amylase isoenzymes (especially isoenzyme 3) and significantly increased theβ-amylase isoenzymes (especially isoenzyme d, e, f, g) of wheat seeds under salt stress. These results suggested that NO is involved in promoting wheat seed germination under salt stress mainly via alleviating the decrease of theβ-amylase activity under salt stress.100 mmol/L NaCl treatment markedly reduced the leaf chlorophyll content but increased electrolyte leakage and MDA content of the leaves. Interestingly, 0.06 mmol/L SNP pre-treatment significantly alleviated the oxidative damage in wheat seedlings under salt stress. Addition of 0.06 mmol/L SNP was able to increase the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) of wheat leaves under salt stress. These results suggested that pre-soaking seeds with NO donor (SNP) increased the salt-tolerance of wheat seedlings partly due to alleviating the oxidative damage induced by salt stress.Additionally, priming of seeds with exogenous NO donor 0.06 mmol/L SNP for 24 h markedly alleviated the osmotic stress caused by 100 mmol/L NaCl. Furthermore, SNP treatment decreased the Na~+ content, but increased the K~+ content and K~+ /Na~+ ratio of wheat seedlings under salt stress. Priming of seeds with 0.06 mmol/L SNP for 24 h almost did not affect V-H~+-ATPase activity but significantly increased V-H~+-PPase activity compared with NaCl treatment alone.