褪黑素减轻猕猴桃果实冷害与碳水化合物代谢的关系

Melatonin Alleviates Chilling Injury in Kiwifruit and Its Relationship with Carbohydrate Metabolism

摘要:

为探究褪黑素（Melatonin，MT）处理减轻猕猴桃果实冷害与碳水化合物代谢的关系，该研究以“徐香”猕猴桃为试材，经0.05 mmol/L MT溶液浸泡处理后，置于0~1 ℃冷藏90 d，并定期测定冷害指数、硬度、丙二醛含量和碳水化合物代谢相关指标。结果显示：MT处理延缓了果实冷害指数的增加，硬度的下降和丙二醛的生成，减轻了冷害的发生；抑制了总淀粉酶活性，贮藏期间，MT处理果实的酶活性较对照平均低41.27%，进而延缓了淀粉向可溶性糖的转化，使果实保持了较高的淀粉含量（1.07%），且MT处理果实的淀粉含量与冷害指数呈极显著负相关关系（r=-0.820，p<0.01）；下调了蔗糖磷酸合成酶、蔗糖合酶、酸性转化酶和中性转化酶活性，贮藏结束时，MT处理果实的酶活性分别较对照低9.52%、9.12%、8.55%和9.74%，从而消弱了果实的蔗糖合成-裂解循环，减缓了果实中蔗糖的积累，这在一定程度上诱导了果实中淀粉降解的延迟。综合分析认为，淀粉可能是猕猴桃果实冷害发生的一个重要生物标志物，MT处理对淀粉含量的影响可能是其对总淀粉酶活性和蔗糖合成-裂解循环共调控的结果。

Abstract:

In order to investigate the relationship between the reduction of chilling injury in kiwifruit by the melatonin (MT) treatment and the carbohydrate metabolism of the fruit, ‘Xuxiang’ kiwifruit was used as the experimental material. The kiwifruits were soaked in the 0.05 mmol/L MT solution and stored at 0~1 ℃ for 90 d. The chilling injury index, firmness, malondialdehyde content and carbohydrate metabolism-related indicators were measured regularly. The results showed that the MT treatment delayed the increase of fruit chilling injury index, the decrease of firmness and the production of malondialdehyde, thus alleviated chilling injury in the kiwifruits. The total amylase activity was found to be inhibited, and during the whole storage, the total amylase activity of the MT-treated fruit was reduced by 41.27% on average compared with that of the control, thereby causing a delayed conversion of starch to soluble sugars, and consequently a higher retained starch content (1.07%) in the kiwifruits. Moreover, the starch content in the MT-treated fruit was significantly negatively correlated with the fruit’s chilling injury index (r=-0.820, p<0.01). The MT treatment decreased the activities of sucrose phosphate synthase, sucrose synthase, acid invertase and neutral invertase, and at the end of the storage, the activities of the four enzymes in the MT-treated fruit were 9.52%, 9.12%, 8.55% and 9.74% lower than those of the control, respectively. Thus, the synthesis-degradation cycle of sucrose was weakened and sucrose accumulation in the fruit slowed down, which induced, to some extent, the delay of starch degradation in the kiwifruit. The comprehensive analysis suggested that starch may be an important biomarker for the occurrence of chilling injury in kiwifruit, and in the effect of MT on kiwifruit may be a result of the co-regulation of total amylase activity and sucrose synthesis-degradation cycle.