Effects of Microwave Treatment on Vigor and Physiological Characteristics of Aged Platycladus orientalis Seeds

To solve the problems of aging and low vigor of Platycladus orientalis seeds, this study used P. orientalis seeds subjected to artificial accelerated aging via high-temperature and high-humidity methods. Germination indices of P. orientalis seeds under different aging durati-ons were measured. Aged seeds (4 days) were then treated with microwave at three power levels (300 W, 500 W, 600 W; denoted as W3, W5, W6) and 4 exposure times (10 s, 20 s, 40 s, 60 s; denoted as T1, T2, T4, T6). The following parameters were evaluated: germination percentage, relative electrical conductivity, malondialdehyde (MDA) content, soluble sugar (SS) content, soluble protein (SP) content, superoxide dismutase (SOD) activity, peroxidase (POD) activity, and adenosine triphosphate (ATP) content. A comprehensive evaluation of different microwave treatments was conducted using the membership function method. The resultsshowed that after aging treatment, the germination percentage, germination potential, germination index, and vigor index of P. orientalis seeds significantly decreased. The germination percentage of seeds aged for 4 days declined from 86.67% to 69.67%. As microwave power and exposure duration increased, the germination percentage, antioxidant enzyme activities, reserve nutrient content, and ATP levels of aged P. orientalis seeds exhibited an initial increase followed by a subsequent decrease. Conversely, relative electrical conductivity and malondialdehyde (MDA) content demonstrated an initial decline followed by a rise. Among all treatments, the 300 W for 40 s (W3T4) protocol significantly enhanced germination percentage, antioxidant e-nzyme activities, reserve nutrients, and ATP content compared to the control, while simultaneously reducing relative electrical conductivity and MDA levels. Prolonged exposure to high-power (600W) microwave treatment (W6T6) exerted inhibitory effects on seed germination. Consequently, the appropriate microwave treatment promotes the germination of aged P. orientalis seeds, with the 300 W 40 s (W3T4) treatment demonstrating the most effective results.