乙酰水杨酸和乙烯处理对猕猴桃果实后熟软化的影响

以猕猴桃(Actinidia deliciosa(A.Chev.)C.F.Liang et A.R.Ferguson cv.Bruno)果实为试材,研究乙酰水杨酸(ASA)与乙烯处理对果实内源水杨酸(SA)含量变化以及后熟软化相关因子的影响,探讨SA在果实成熟衰老进程的作用.研究结果表明:果实后熟软化进程中,内源SA水平呈下降变化,组织中SA水平与果实硬度变化呈极显著正相关关系(r=0.969 4**),ASA处理可显著地维持组织中较高的SA水平,抑制脂氧合酶(LOX)和丙二烯氧合酶(AOS)活性增加,减低O-.2生成速率,维持细胞膜稳定性,进而抑制了乙烯生物合成或推迟乙烯跃变的到来,延缓了果实后熟软化进程,这些效应主要表现在乙烯跃变之前或乙烯跃变前期;相反,外源乙烯处理则显著降低果实组织中内源SA水平,促进LOX和AOS活性的增加,促使O-.2积累,增加了细胞膜透性,促使乙烯跃变的提前到来,加速了果实的后熟软化.推测组织中的内源SA水平与细胞膜脂过氧化作用密切相关,外源ASA可能作为一种O-.2等自由基的清除剂或是细胞膜稳定剂在组织成熟衰老过程中起作用.

Effects of Acetylsalicylic Acid(ASA) and Ethylene Treatments on Ripening and Softening of Postharvest Kiwifruit

Kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson cv. Bruno) was used to investigate the effects of acetylsalicylic acid (ASA, 1.0 mmol/L, pH 3.5) and ethylene (100 mL/L) treatments on changes at endogenous salicylic acid (SA) levels and other senescence-related factors during fruit ripening and softening at 20 ℃. The level of endogenous SA in ripening fruits declined and a close relationship was observed between the change at endogenous SA level and the rate of fruit ripening and softening. ASA treatment elevated SA level in the fruit, slowed down the increases in lipoxygenase (LOX) and allene oxide synthase (AOS) activities, decreased the O22-. production in the preclimacteric phase and the early phase of ethylene climacteric rise, maintained the stability of cell membrane, inhibited ethylene biosynthesis, postponed the onset of the ethylene climacteric, and delayed the process of fruit ripening and softening. On the contrary, application of ethylene to ripening kiwifruit resulted at a lower SA level, an accelerated increases in the activities of LOX and AOS and the rate of O22-. production, an elevated relative electric conductivity and an advanced onset of ethylene climacteric, and a quicker fruit ripening and softening. It is suggested that the effects of ASA on ripening kiwifruit can be attributed to its ability to scavenge O22-. and/or to maintain stability of cell membrane.