As a common physiological disorder caused by high temperatures and/or intense light, apple fruit sunburn results in a great loss every year. With popularization of dwarf rootstocks adaptable to native conditions in China, coupled with the prevailing tendency of global warming, it could be expected that the injury caused by high temperatures and/or intense light will be aggravated in the near future, and thus it is necessary to intensify the studies on the prevention of this disorder in advance.A series of physiological process must undergo inside a fruit before it shows sunburned symptoms. Therefore, understanding of this process is beneficial to controlling it. However, littlie has been known so far about the mechanism concerning these respects. Using resistant-biological principles and methods, the present experiment was undertaken to reveal the responsive patterns of Fuji apples to the stresses caused by high temperature and/or intense light, as well as the efficacy of antioxidants on adjustment of fruit antioxidative capability.1. Under natural conditions, a great difference in antioxidative properties existed among fruit on different canopy exposures, as influenced by distinctive reception of solar radiation and other ecological parameters. Fruit on west, southwest and south exposures received more light in the afternoon than the other exposures, so that daily maximum fruit surface temperatures were higher. However, the light intensity received by fruit inside the canopy was so weak that fruit temperature was merely close to air temperature. For this reason, fruit on west, southwest and south exposures were generally stressed more than those on other exposures, showing higher contents of O2- and MDA with an increase of antioxidant contents and antioxidative enzymatic activities in common cases.2. Within a certain range, the activity of antioxidative enzymes increased with the severity of fruit sunburn but decreased sharply beyond the limit. Similarly, MDA and O2- contents rose with the severity of fruit sunburn but no increase was found when fruit symptoms reached a certain degree. As far as two types of antioxidants were concerned, Vitamin C content decreased while Car... |