Effects of Exogenous NO on the Physiological Characteristics and Anatomical Structure of Fatsia japonica Leaves under Salt Stress

To study the effects of exogenous nitric oxide(NO) on physiological characteristics and the anatomical structure of Fatsia japonica leaves under salt stress(NaCl). The half-year-old Fatsia japonica was treated with 1.2% NaCl solution by pot experiment, and exogenous NO donor(15 mL, 0.1 mmol/L Nitroprusside Sodium) was sprayed on the leaf surface for a total of 30 processing days. Photosynthetic parameters and physiological indexes were measured at 0 d, 15 d(mild) and 30 d(moderate) after salt treatment, and observed the anatomical structure of leaves. The results were as follows: Fatsia japonica was able to adapt to mild salt stress by increasing the activity of antioxidant enzymes, accumulating Pro, adding thickness to the cuticle and main veins. However, moderate salt stress significantly reduced the photosynthesis, RWC, photosynthetic pigment, and SS content in the leaves of Fatsia japonica, leading to a significant accumulation of MDA(malondialdehyde) and disorganized mesophyll tissue, with a marked thinning of leaf thickness. The application of exogenous NO(nitric oxide) effectively mitigated the reduction in photosynthesis under salt stress, significantly increased leaf RWC, and the content of photosynthetic pigments, SS, and SP, enhanced CAT and APX activities, and markedly reduced MDA levels. In addition, exogenous NO also reduced the thickness of the upper epidermis and cuticle layer, promoted mesophyll growth, increased the ratio of palisade to spongy tissue, and enhanced the salt tolerance of Fatsia japonica. In summary, Fatsia japonica has a certain degree of salt tolerance, and the application of exogenous NO can effectively alleviate the damage caused by moderate salt stress to Fatsia japonica leaves and enhance its resistance to salt stress.