Abstract:

Objective: This study investigated the effects of different concentrations of betaine (BT), salicylic acid (SA), methyl jasmonate (MeJA) and calcium chloride (CaCl₂) on stress resistance of Erythrophleum fordii seedlings under drought stress, in order to find a feasible method to alleviate the drought damage of E. fordii seedlings, and provide technical reference for the cultivation and promotion of E. fordii. Method: The annual E. fordii seedlings were used as materials. Different concentrations of BT, SA, MeJA and CaCl₂ solutions were sprayed on the leaves, and then the root system with the culture medium was dipped in a concentration of 30% PEG-4000 solution for simulating a drought stress. Two groups of controls (CK) were set up. CK₁ was sprayed with distilled water on the leaves and the root was maintained in a normal soil environment. CK₂ was sprayed with distilled water on the leaves and the root system was placed in a concentration of 30% PEG-4000 solution. Cell membrane permeability, malondialdehyde (MDA), proline (PRO), soluble protein, soluble sugar, chlorophyll content (SPAD value), and superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) antioxidant enzyme activity of E. fordii seedlings leaves were measured on the 10th day after drought stress treatment. Result: Compared with CK₁, drought stress significantly inhibited the antioxidant enzyme activities of leaves of CK₂, and aggravated the damage of cell membrane by drought conditions, resulting in damage to cell membrane structure and destruction of cell membrane function, which led to significant increases in relative conductivity and MDA content of leaves of seedlings. Drought stress was also able to cause the destruction of chloroplast structure, and hence impeded normal photosynthesis. Compared with CK₂, foliar application of signal substances significantly increased the content of PRO, soluble protein and soluble sugar in the leaves, and reduced the water loss caused by drought in leaves of seedlings. In addition, the foliar application of signal substances improved POD, SOD and CAT antioxidant enzymes, andactively and effectively removed excess reactive oxygen species in cells, avoided membrane lipid peroxidation, significantly reduced leaf MDA content and relative conductivity, normalized cell membrane system metabolism, and alleviated the damage caused by drought stress on leaves of seedlings. The foliar application of signal substances increased the SPAD value of leaves and reduced the inhibition of photosynthesis by drought. With the increase of the treatment concentration, except for the CaCl₂ solution, the other three kinds of exogenous signal substances hada tendency to attenuate the drought damage to the seedlings. Conclusion: Foliar application of 500 mg·L^-1 BT, 100 mg·L^-1 SA, 1 mmol·L^-1MeJA, and 5 mmol·L^-1 CaCl₂ solution can significantly alleviate drought stress and improve the drought resistance of E. fordii seedlings.

Key words: Erythrophleum fordii, drought stress, regulating chemicals, physiology and biochemistry