【作者】 朱世江；

【导师】 季作梁；

【作者基本信息】 华南农业大学 ， 果树学， 2001， 博士

【摘要】 芒果原产热带亚热带,成熟时正值高温季节,常温下容易腐烂,不耐贮藏; 低温贮藏易发生冷害。热处理可以提高芒果抗冷性,而且,热处理作为一种物理的果实保鲜方法,与化学保鲜剂相比具有无农药残留、不污染环境等优点。但是,热处理的保鲜机理还有许多不清楚的地方。本研究以芒果为试材,从形态解剖,生理变化,蛋白质合成及含量组分变化动态等方面较系统地考察热处理提高采后抗冷性的的机理,结果如下: 热处理使芒果获得较强抗冷性所需要的时间因处理方式和温度不同而有很大差异,55℃或56℃热水处理只需3min,38℃热空气处理需要12h以上; 38℃热空气处理持续时间在12～72h范围内均可使芒果获得较强抗冷性; 芒果经38℃热空气处理1～3d后在常温(20℃)下存放2～4d,抗冷性依然保持。经热处理的芒果在冷害温度2℃下贮藏11d后能够正常后熟,而对照在2℃贮藏11d后发生严重冷害,不能正常后熟。38℃热空气处理3d可以使芒果在2℃贮藏期间与对照发生同等冷害的时间推迟15d。热处理还可减少芒果腐烂,增强其的商品性。55℃热水处理3～5min可以作为减轻芒果冷害和腐烂的有效措施在生产上推广应用。透射电镜观察表明,热处理能使芒果细胞结构及内膜系统在2℃冷藏15d后仍表现正常,而对照的细胞则发生严重质壁分离,内膜系统受到严重破坏,特别是叶绿体畸形,内部出现空腔,甚至叶绿体的外膜消解,基粒片层排列散乱。热处理使2℃冷藏10～12d后的芒果果皮的膜透性低于对照,而热处理期间的膜透性变化因处理方式和温度不同而异:38℃热空气处理(3h～72h)期间膜透性升高,而55℃热水处理(3～15min)期间膜透性下降。在热处理期间芒果细胞内发生了一系列有利于保护细胞膜的生理变化。本研究通过对38℃热空气处理期间以及2℃低温贮藏期间芒果的生理变化的考察表更多还原

【Abstract】 The mechanism of induction of chilling tolerance of mango by heat treatment was systematically investigated based on the observation on the changes in anatomy, physiology and the synthesis, contents and composition of proteins. The time duration of heat treatment required for inducing chilling tolerance in mango fruits varied with the temperature and the manners of treatment. While 3 min was enough for hot-water treatment (HWT) at 55～56℃, at least 12h was needed for hot air treatment (HAT) at 38℃, to induce chilling tolerance in mango, with any length between 12～72h of HAT being of almost the same effect, as far as the chilling tolerance is concerned. Heat treatment could make a difference of 15d from the control under cold storage at 2℃. 2～4d at 20℃ following 1～3d at 38℃ reduced little of the acquired chilling tolerance. Heated mango ripened normally after storage at 2℃ for 11d, but the control suffered from serious chilling injury and couldn’t ripen normally. Heat treatment inhibited rotting and remarkably enhanced external quality of mango fruits. 3～5min of hot water soaking at 55℃ is recommended for extension to farmers as an alternative to reduce chilling injury and rotting. Observation through Trans-electronic Microscope showed that after cold storage for 15d the membrane system of the cell of mango was seriously damaged, especially the chloroplasts, while heat pretreatment prevented such damages from happening. This was coincided with the levels of ion leakage, which was lower in heat-treated mango than in control after 12d at 2℃. However, during heat treatment, different trends in ion leakage were revealed for the two different types of heat treatments. While 38℃ hot air treatment increased the ion leakage level, 55℃ hot water treatment reduced it. In order to understand the physiological mechanism of heat treatment in inducing chilling tolerance, the physiological effects of HAT on mango were studied. The results showed that heat treatment induced a series of physiological changes in the cells of mango fruits, which helped to induce chilling tolerance. The induction of the chilling tolerance in mango was correlated with high levels of SOD, POD and PAL activities and high rates of IAA and ABA during cold storage at 2℃. The investigation on the physiological pattern of mango during heat treatment and cold storage showed that the physiological changes during heat treatment were the bases and the causes of the physiological differences between heat treatment and control during cold storage at 2℃. The peel and the flesh of mango, although closely linked physically, displayed different trends physiologically. Physiological observation of both peel and flesh is necessary for the precise understanding of the inducing mechanism of chilling tolerance. Among all the changes caused by heat treatment, the heat-shock proteins (HSPs) were most closely and most directly connected with the induction of chilling tolerance. Within 24h of HAT, the rate of protein synthesis in mango peel was much higher than that at normal temperature, which indicated that the high-speed synthesis of HSPs could last at least 24h. During HAT, the content of proteins increased continuously, while that at room temperature or low temperature showed no obvious change. Among the proteins accumulated during HAT, heat-stable proteins took a larger part. This indicated that HSPs newly synthesized were mainly made up of heat-stable proteins. And it was probably these heat-stable proteins that were correlated with the induction of chilling tolerance. The results of the electrophoresis analysis further supported the close link between the HSPs and the chilling tolerance.in mango fruits. The most direct proof acquired for the link was found in fruits partially exposed to HWT, with the exposed part ripened normally and the other part showed black symptoms of chilling injury. The two-dimensional electrophoresis diagrams of proteins extracted from the two different parts were on the whole similar to each other. However, in the diagram from the exposed part there were 6 new proteins of molecular weights (MW) of 13.7, 15.7, 28.5, 38.1, 59.1 kD, respectively (including two proteins of the same MW and of different iso-electric point), which didn’t exist in the non-heated part. Another proof for the link between new HSPs and chilling tolerance came from a set of mango fruits with degrees of chilling injuries ranging from very serious to very slight as a result of varying duration of exposure of fruits to HAT. The HAT duration of 3h, 6h and 24h induced 2, 5 and 7 new HSPs, respectively, though these proteins were mostly different in MW from those induced by HWT. The extent of chilling tolerance increased with the number of new HSPs. The persistence of the HSPs in mango fruits also accounted for the chilling tolerance. 2～4d at 20℃ following 1～3d at 38℃ affected little of the acquired chilling tolerance of mango fruits. This coincided with the fact that the HSPs decayed very little during the short period at 20℃. Moreover, most of the HSPs induced by HAT continued to exist after cold storage at 2℃ for 11d. The big difference between HAT and HWT in the length of time needed for inducing chilling tolerance and in the compositions of newly produced HSPs indicated that the mechanisms of new HSPs induction and chilling tolerance formation were possiblly different for the two kinds of heat treatments.更多还原