外源一氧化氮(NO)对低温胁迫下南瓜幼苗氧化损伤的保护效应

探讨外源 NO 供体硝普钠(SNP)对冷害胁迫下南瓜生长和氧化损伤的内在机制。以南瓜银辉2号和青栗为材料,通过室内人工模拟低温逆境的方法,研究 SNP(100 μmol/L)对冷害胁迫下南瓜幼苗生长、叶绿体色素含量、有机渗透调节物质含量及活性氧代谢的影响。结果表明,冷害导致南瓜幼苗活性氧积累增加,膜质过氧化加剧,光合色素含量下降,渗透调节能力降低,从而显著抑制南瓜幼苗的生长;正常生长条件下, SNP显著提高了超氧化物歧化酶(SOD)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性,显著增加幼苗地上和地下部干重及谷胱甘肽(GSH)、过氧化氢(H₂O₂)、类胡萝卜素和氨基酸总量;8 ℃/5 ℃(昼/夜)的低温胁迫下,叶面喷施外源100 μmol/L NO供体硝普钠(SNP),促进了植株生长和干物质积累,显著提高了叶片SOD、POD、APX 和GR的活性以及Pro和可溶性糖含量,减少了H₂O₂和膜脂过氧化产物丙二醛(MDA)的积累;外源NO明显提高了南瓜叶片叶绿素、类胡萝卜素含量、抗坏血酸(ASA)、GSH和可溶性蛋白及氨基酸总量。低温胁迫下,外源NO通过促进抗氧化酶活性、抗氧化剂及有机渗透调节物质含量的提高,降低H₂O₂和MDA的积累,保护了细胞膜结构的稳定性,维持了冷害下南瓜幼苗碳氮代谢的正常进行,增强了南瓜的抗冷性。试验条件下,NO对银辉2号的促进作用大于青栗。

Protective effect of exogenous nitric oxide against oxidative damage in pumpkin seedlings under chilling stress

The effects of exogenous nitric oxide on growth and oxidative damage in pumpkin seedlings under low temperature stress were studied. Seedlings of two pumpkin cultivars, ‘Yinhui 2’ and ’Qingli’, were sprayed with the nitric oxide donor, sodium nitroprusside (SNP: 100 μmol/L) and their growth, chloroplast pigment content, organic osmoregulation substances content, and active oxygen metabolism under chilling stress were analyzed. Chilling stress significantly inhibited the growth of pumpkin seedlings as a result of increased active oxygen accumulation and lipid peroxidation, decreased photosynthetic pigment content, and reduced osmotic adjustment ability. Under normal growth conditions, the SNP treatment significantly increased the activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR), and also significantly increased shoot dry weight, root dry weight, and the H₂O₂, free amino acid, glutathione, and carotene contents. Under chilling conditions (8 ℃ days/5 ℃ nights), seedlings sprayed with 100 μmol/L SNP showed significantly increased plant growth and dry matter accumulation and significantly increased SOD, POD, APX and GR activities in leaves, and reduced accumulation of H₂O₂ and malondialdehyde (MDA). Exogenous SNP application increased the glutathione, chlorophyll, carotenoid, ascorbate, soluble protein, and total amino acid contents. Under chilling stress, exogenous SNP application reduced the accumulation of H₂O₂ and MDA, and protected membrane stability by increasing antioxidant enzyme activities and the contents of organic osmoregulation and antioxidant substances. These physiological changes protected the stability of cell membrane structure, and maintained carbon and nitrogen metabolism in the seedlings under chilling conditions, thereby increasing the cold resistance of pumpkin. Under these conditions, Yinhui 2 was more responsive than Qingli to exogenous SNP.