Abstract:

In order to investigate the physiological regulation mechanism of exogenous H₂O₂ on the cotton seedlings under NaCl stress,the cotton variety Xinluzao 48 was used as the test material in an outdoor potting method.Two-factor random combinations of salt stress (NaCl,concentration gradients of 0,100,200 mmol/L) and H₂O₂ (concentration gradients of 0,0.005,0.010,0.020,0.050 mmol/L) were set,to study the change rule of fresh weight,dry weight,chlorophyll content,chlorophyll fluorescence parameters,photosynthetic gas parameters,antioxidant enzyme activities and osmotic regulation system of cotton seedlings.The results showed that exogenous H₂O₂ effectively alleviated the inhibitory effect of salt stress on the growth of cotton seedlings,increased chlorophyll content,photosynthetic gas parameters and chlorophyll fluorescence parameters of cotton seedlings,maintained the normal operation of photosynthesis of cotton seedlings and ensured the accumulation of dry matter.Meanwhile,exogenous H₂O₂ could increase the activity of antioxidant enzymes (POD,APX,CAT),accelerated the removal of ROS from cotton seedlings.Exogenous H₂O₂ reduced the electrolyte leakage rate,MDA content,the content of osmoregulation substances such as pro,free amino acid and SS,and improved the salt resistance of cotton seedlings.Among all treatment,0.020 mmol/L exogenous H₂O₂ had the best effect in alleviating the salt stress suffered by cotton seedlings.In summary,exogenous H₂O₂ improves the adaptation of cotton seedlings to salt stress by improving photosynthetic performance,keeping stable photosynthesis in cotton seedlings,and maintaining the dynamic balance between ROS production and elimination in cotton seedlings.

Key words: Cotton seedlings, Salt stress, Exogenous H₂O₂, Photosynthetic performance, Antioxidant enzyme system