Abstract:

Salt stress is one of the major abiotic stresses restricting chili pepper （Capsicum annuum L.） production. This study elucidated the regulatory role and physiological mechanism of iron chlorine e6（ICE6），a novel plant growth regulator，in enhancing salt tolerance of chili pepper. A salt stress experiment with 200 mmol?L^-1 NaCl was conducted to systematically analyze the effects of exogenously sprayed ICE6 on seed germination，seedling growth，key physiological and biochemical indexes，and the expression of salt-tolerant genes. The results showed that compared with the NaCl treatment，the ICE6+NaCl treatment significantly（p<0.05）increased the seed germination rate by 31.66 percentage points and the germination index by 76.79%，while significantly reduced the relative salt damage rate，effectively mitigating the inhibitory effect of salt stress on seed germination of chili pepper. At the seedling stage，ICE6 application significantly alleviated salt stress symptoms. Compared with the NaCl treatment，the relative electrical conductivity of the ICE6+NaCl treatment significantly decreased by 18.61，25.07，26.72，12.02 and 7.73 percentage points at 12，24，36，48，60 h，and significantly elevated the activities of peroxidase（POD）and superoxide dismutase（SOD）at 6-24 h. After 24 h of ICE6+NaCl treatment，the expression levels of salt-tolerant genes CaNAC55 and CaEIL8 were significantly up-regulated. These findings lay a theoretical basis for the application of ICE6-based bioregulators in pepper cultivation，and provide a feasible strategy for improving salt tolerance in crops.

Key words: iron chlorine e6, Capsicum annuum L., salt stress, physiological characteristic, gene expression