根际低氧胁迫对网纹甜瓜生长、根呼吸代谢及抗氧化酶活性的影响

Impacts of root-zone hypoxia stress on muskmelon growth,its root respiratory metabolism,and antioxidative enzyme activities

采用气雾法栽培系统,研究了根际低氧(10%O2和5%O2)胁迫对网纹甜瓜果实发育期间植株生长、根呼吸代谢及抗氧化酶活性的影响.结果表明:与对照相比,低氧胁迫下,网纹甜瓜株高、根长降低,植株鲜、干物质量显著下降;根呼吸速率极显著低于对照(21%O2),且5%O2处理下降幅度大于10%O2处理;乳酸脱氢酶(LDH)、乙醇脱氢酶(ADH)和丙酮酸脱羧酶(PDC)活性较对照显著升高,而苹果酸脱氢酶(MDH)活性显著降低;根系中超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性和丙二醛(MDA)含量显著高于对照,其中10%O2处理抗氧化酶活性升高幅度显著大于5%O2处理,而MDA含量5%O2处理高于10%O2处理.说明网纹甜瓜果实发育期间根际氧浓度降到10%及其以下时,根系有氧呼吸明显受阻,无氧呼吸代谢被促进,同时根系抗氧化酶发生应激反应,但随低氧胁迫时间的延长,根细胞质膜过氧化程度加剧,根系受到伤害,植株生长受到抑制,最终导致果实产量和品质下降.

By using aeroponics culture system,this paper studied the impacts of root-zone hypoxia（10% O2 and 5% O2）stress on the plant growth,root respiratory metabolism,and antioxidative enzyme activities of muskmelon at its fruit development stage. Root-zone hypoxia stress inhibited the plant growth of muskmelon,resulting in the decrease of plant height,root length,and fresh and dry biomass. Comparing with the control （21% O2）,hypoxia stress reduced the root respiration rate and malate dehydrogenase （MDH） activity significantly,and the impact of 5% O2 stress was more serious than that of 10% O2 stress. Under hypoxic conditions,the lactate dehydrogenase （LDH）,alcohol dehydrogenase （ADH）,pyruvate decarboxylase （PDC）,superoxide dismutase （SOD）,peroxidase （POD）,and catalase （CAT） activities and the malondialdehyde （MDA） content were significantly higher than the control. The increment of antioxidative enzyme activities under 10% O2 stress was significantly higher than that under 5% O2 stress,while the MDA content was higher under 5% O2 stress than under 10% O2 stress,suggesting that when the root-zone oxygen concentration was below 10%,the aerobic respiration of muskmelon at its fruit development stage was obviously inhibited while the anaerobic respiration was accelerated,and the root antioxidative enzymes induced defense reaction. With the increasing duration of hypoxic stress,the lipid peroxidation would be aggravated,resulting in the damages on muskmelon roots,inhibition of plant growth,and decrease of fruit yield and quality.