【作者】 李英丽；

【导师】 张建光；

【作者基本信息】 河北农业大学 ， 果树学， 2003， 硕士

【摘要】 苹果果实日灼是一种常见的主要由高温和强光引起的生理伤害，每年在世界各主要产区都有发生，使产量和质量受到不同程度的影响。随着适合我国自然条件的抗性苹果矮化砧的逐渐推广，加上我国环境条件的进一步改善和受全球气候逐渐变暖趋势的影响，未来果实的高温和强光伤害必然会成为影响我国苹果产量和品质的一个值得重视的问题，因此需要加强在这方面的研究， 果实外表发生日灼症状之前必然要经历一系列生理生化变化过程，了解这个过程对于深入探讨调控措施极为关键。然而，迄今对果实日灼生理过程方面的研究甚少。本试验应用现代生物学基本原理和方法，探索了高温和强光胁迫条件下苹果果实的反应规律及其抗性机理，主要研究结果如下： 1．自然条件下，树冠不同方位果实生理状态有很大差异。树冠西南面最易发生高温和强光胁迫。生长季晴天树冠西南面果实接受的日最大光照强度比其它四个方位（东北、东、北、西北）高300W/m²～630W/m²，果面日最高温度比其它四个方位高5℃～6.5℃。一般在亚致死高温强光胁迫条件下，处于树冠西南方外围充分暴露的果实，其表皮组织中超氧阴离子自由基和MDA含量以及SOD和POD活性都高于其它方位的果实。 2．果实表皮组织中超氧阴离子自由基，SOD、POD和MDA对高温和强光胁迫的反应比较敏感。在一般高温（亚致死高温）和强光胁迫下，自由基能够迅速产生，其含量在胁迫1h内达到高峰，从而刺激诱导了细胞内过氧化保护系统功能的发挥，致使SOD和POD活性明显增加，SOD、POD活性一般在胁迫3小时左右达到高峰，而MDA含量一般在胁迫5小时左右达到高峰。如果发生的是轻微胁迫，果实内保护酶系统可以消除少量活性自由基和过氧化物的影响，在此情况下，MDA含量变化并不明显；但如果胁迫程度较重，果实内抗氧化保护系统（包括抗氧化酶和抗氧化剂）不足以消除其危害，细胞就会受到一定程度的损伤，导致MDA含量显著增加。 3．果实日灼症状出现前后，表皮组织中SOD和POD活性变化趋势有所不同。果实日灼症状出现前，在一定高温和强光胁迫范围内，细胞内保护性酶SOD和POD随着胁迫的加重而上升，以消除环境胁迫带来的不利影响；但在果实日灼症状出现后，保护酶的作用行为便发生了变化。随着日灼程度的加重，SOD可能由于自身受到伤害而导致活性下降，但POD活性仍然在继续升高。 4．外源自由基产生剂能够影响果实内源超氧阴离子自由基的代谢。一般用不同种类的外源自由基产生剂处理果实后，均可增加内源O₂^-·的含量，提高SOD和POD的活性。就本试验而言，果实内OZ－·含量增加 14．52W61．70％，SOD的活性增加1刀7～1．66倍：P＊D活性增加0．6刚3．5倍。不同种类外源活性氧产生剂对内源活性氧含量影响的效能有所不同。碱性二亚硫酸钠可直接产生O。’·，所以刺檄诱导内源O。－·生成的效果更好一些。 5．一般生长季晴天，袋内果实表面最高温度总是高于不套袋的果实。以本试验所采用的四种袋型作比较，袋内果实日最高温度比对照提高2．5℃～6．0℃。所以，可以说套袋果实经常遭受袋内高温胁迫的影响。除袋后将果实暴露在光下，四种袋、型处理果实表皮组织OZ’·含量比对照提高 16．2lW60．29％；但 SOD和 POD活性以及MDA含量变化随着袋型的变化而有所差异。 6．果实日灼症状发生的主要生理机制是：在高温和强光共同胁迫下，果实内超氧阴离子白由基代谢紊乱，细胞内抗氧化系统不足以消除其危害，囚而致使细胞膜系统遭受伤害，膜透性增加，细胞质大量外溢，一些酚类物质氧化变褐，直至出现不同程度的日灼症状。更多还原

【Abstract】 Apple fruit sunburn, a common physiological disorder caused by higher temperature and intense sunlight, occurs everywhere in main apple-producing areas on the world every year, resulting in a severe loss of both fruit yield and quality. As new dwarfing rootstocks suitable to the Chinese climate and soil conditions are popularized, together with improvement of our environment and the influence of global warming-up caused by "greenhouse effect", this disorder will become a severe problem which undoubtedly affect the apple industry in China. Therefore, a study is needed urgently in this field.The prerequisite for fruit sunburn occurrence is that, fruit surface have to reach the "threshold temperature" which depend largely upon air temperature and solar radiation at the moment. However, the study on physiological aspect of fruit sunburn is very limited so far. The present test is undertaken to study the response and mechanism of apple fruit to higher-temperature and intense-light stress by means of application of basic principles and methods in modern biology. The main results are as follows:1. Under natural conditions, there is a considerable difference in physiological status of fruit on different exposures on a canopy. The higher-temperature and intense-light stress frequently happens on the southwest exposure. In a clear and sunny day, the light intensity received by the fruit on southwest canopy is 30,000~60,OOOLux more than those from northeast, east, north and northwest exposures, and maximum fruit surface temperature is 5"C~6.5*C higher. Under sub-lethal temperature stress, the contents of O2- and MDA as well as the activities of SOD and POD in the fruit on southwest canopy are significantly higher than those from other exposures.2. The changes of O2- SOD, POD and MDA in fruit peel are sensitive to higher-temperature and intense-light stress. Under sub-lethal temperature stress, O2-can be generated quickly and the peak occurs within Ih immediately after the stress. Moreover, it can increase the activities of SOD and MDA, which may attain themaximum values at about 3rd- and 5th h, respectively. If light stress happens, the protective enzymes could eliminate less amount of O2 ’, and in this case no apparent changes will be found in the content of MDA. If severe stress happens, however, the protective enzymes will be deteriorated, resulting in a marked rise of MDA content.3. A difference of enzymatic action with SOD and POD is documented in different stages of fruit sunburn. Before sunburn symptoms appear, the activities of SOD and POD increase within a certain range of stress, but after sunburn symptoms are visual, the SOD activity decreases with the advance of fruit sunburn. In contrast, the activity of POD continues to increase during this period.4. Exogenous free-radical agents could change the metabolism of endogenous O2- And different types of exogenous free-radical agents can consistently increase endogenous O2- content and raise the activities of SOD and POD. As far as the present test is concerned, the O2- content in fruit peel increases by 14.52%61.70%, the SOD activity by 1.07-1.66 times and POD activity by 0.6-3.5 times. A differential effect of exogenous free-radical agents on endogenous O2- production may exist with Na2S2O4, showing a more powerful agent.5. In a clear day, the surface temperature of bagged fruit is always higher than the exposed fruit, with the treatments with four types of bags exhibiting 2.5癈~6.0癈 higher than that from the control. After bags are removed, the O2- contents in fruit peel increase by 16.21%~60.29%. However, the activities of SOD and POD as well as MDA content vary with various kinds of bags.6. The mechanism of fruit sunburn occurrence could be described as the following: under higher-temperature and intense-light stress, a disturbance of free radicals in fruit peel takes place and the protective enzymes are insufficient to eliminate the injury cause by free radicals. As a consequence, the membrane is damag更多还原