猕猴桃栽培中易遭受水涝胁迫,造成根际低氧,致使土壤中氧化还原电位和pH 值过低,Mn4+被还原成Mn2+,Mn2+大量积累,进而导致Mn2+毒害。为此,本文采用水培通氮气及不同浓度的锰二因素随机区组的方法,从低氧胁迫和锰对秦美及中华猕猴桃幼苗叶、根抗氧化系统的协同影响方面,研究猕猴桃幼苗体内保护酶对活性氧的清除影响机理。结果表明,低氧条件下,10 和200 μmol/L 锰处理时,随着锰浓度的提高,2 个猕猴桃品种叶、根内超氧化物歧化酶(SOD)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)、抗坏血酸(AsA)活性增加,在清除活性氧方面发挥了重要作用。低氧条件下,10 和200μmol/L 锰处理时过氧化氢酶(CAT)活性明显降低。低氧条件下600 μmol/L 锰处理时,2 个猕猴桃品种叶、根内SOD、POD、CAT、APX、GR 和AsA 活性显著降低,过氧化氢(H2O2)和丙二醛(MDA)含量迅速增加,猕猴桃膜脂过氧化进一步加剧。这表明,高浓度的锰处理不但不能增强猕猴桃对低氧胁迫的抗性,反而会加重低氧对猕猴桃植株的伤害。两种猕猴桃各生理指标变化都表现为一定的相似性,但秦美猕猴桃低氧下对锰的抗性明显高于中华猕猴桃。
Low oxygen concentration is a normal natural environmental stress during kiwifruit cultivating. Under root zone of hypoxia stress, pH and reduction potential would become much lower around the plants' roots. Under this condition, Mn4 + would be deoxygenized to Mn2+, which is the form of manganese absorbed by plants in the soil. If hypoxia soil keeps the low reducing and pH conditions for a long time, Mn2+ will be accumulated to a high concentration, and Mn2+ toxicity to plants may occur. So in this paper, changes of antioxidant enzyme activities of different resistant kiwifruit seedlings (Actinidia. deliciosa var. Qinmei & Actinidia. chinensis var.Qinmei rufopulpa) are evaluated under hypoxia stress with different levels of Mn2+ . Activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxide (APX), glutathione reductase (GR), catalase (CAT), the contents of H2O2, ascorbic (AsA) and malondialdehyde (MDA) are studied to understand how active oxygen damages the membrane lipid under hypoxia stress. Two species' seedlings were planted in hydroponics. Nutrient solutions including different levels of Mn2+ (10, 200, 400 and 600 μmol/L) were aerated with nitrogen in order to induce root zone of hypoxia stress. Eight days later, when symptoms were obvious, antioxidant enzyme activities, contents of H2O2 and malondialdehyde (MDA) were investigated. It is concluded that the right amount of Mn2+ could reduce damages of active oxygen from hypoxia stress, however, a high level of Mn2+ is only to aggravate the damage. The two different resistant kiwifruit species have similar physiological mechanisms, but the A. deliciosa var. seedling is superior to that of A. chinensis var. rufopulpa in terms of anti-active oxygen abilities.
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