采后猕猴桃叶绿素降解机制及1-MCP处理对其代谢的影响

以陕西"秦美"猕猴桃为试材,在(0.0±0.5)℃贮藏条件下,研究猕猴桃叶绿素的降解机制及1-甲基环丙烯(1-methylcyclopropene,1-MCP)处理对猕猴桃叶绿素及其衍生物和相关酶活的影响。结果表明:在猕猴桃果实贮藏过程中,脱植基叶绿素a、脱镁叶绿素a和脱镁叶绿酸a是叶绿素a的主要降解产物,其含量呈先上升后下降的趋势。脱植基叶绿素a和脱镁叶绿酸a的变化趋势分别与叶绿素酶和脱镁螯合酶活性变化趋势一致,由此推断其降解过程遵循叶绿素脱镁叶绿酸a加氧酶降解途径。1.0 μL/L 1-MCP处理可提高猕猴桃果实过氧化物酶活性,抑制叶绿素酶和脱镁螯合酶的活性,减缓叶绿素的降解,抑制脱植基叶绿素a、脱镁叶绿素a、脱镁叶绿酸a的生成,从而延缓果实绿色的降解以及果实的成熟与衰老。研究结果可为1-MCP延缓猕猴桃果实的褪色提供理论依据。

Mechanism of Chlorophyll Degradation and Effect of 1-MCP Treatment on Chlorophyll Metabolism in Postharvest Kiwifruit

Kiwifruits (Actinidia deliciosa cv. Qinmei) were treated at harvest with 1-methylcyclopropene (1-MCP) and then stored at (0.0 ± 0.5) ℃. The mechanism of chlorophyll degradation and the effect of 1-MCP treatment on the contents of chlorophyll and its derivatives and the activities of related enzymes were studied. The results showed that chlorophyllide a, pheophorbide a and pheophytin a were the major degradation products of chlorophyll a during storage. The contents of these three derivatives increased initially and then decreased during storage. The changes in the contents of chlorophyllide a and pheophorbide a were in accordance with the changes in the activities of chlorophylase and Mg-dechelatase, respectively. Therefore, chlorophyll degradation followed the degradation pathway of pheophorbide a oxygenase. The treatment with 1.0 μL/L 1-MCP increased the activity of peroxidase and delayed the maturity and senescence of kiwifruits. 1-MCP inhibited the activities of chlorophylase and Mg-dechelatase, and slowed down the degradation of chlorophyll. 1-MCP restrained the production of chlorophyllide a, pheophytin a and pheophorbide a, and thus delayed the maturity and senescence of kiwifruits. These results provide a theoretical basis for the application of 1-MCP to delay chlorophyll degradation in kiwifruit.