Study On Characteristics Of Physiological Deterioration Of Stored Wheat

Wheat is an living organism with biological characteristics. During wheat storage it will appear in the decrease of the enzyme activity, respiration, germination rate and other physiological deterioration phenomenon, all of this lead to the continued decrease of seed quality and processing quality. In this paper, we chose four varieties of wheat which are widely cultivated in the central of china, and carry on the following research work:(1) By the method of activity tissue staining, we studied the organization location of stored wheat when deteriorated, and evaluated the initial site of wheat physiological deterioration.(2) Using the trace CO2 tester to determine the respiration of wheat in the normal storage condition, then analyzed the respiration characteristics of wheat during physiological deterioration.(3) By the biochemical analysis and microstructure observation, we determined the main physiological enzyme activity and the RNase during wheat storage, and observed the structure of starch granules, the main nutritional components of wheat. The results were as following:(1) Study on the tissue location on wheat physiological deterioration.Observation the stained sections of the wheat embryo at 30℃,40℃ and 50℃ after storing 42 days. Only the cap of root of wheat was not stained red at 30℃, at the same storage time, there were no biological activity in the cap of root and radical at 40℃, the whole embryo of wheat lost all activity at 50℃ after storing 42 days. The results showed that, the physiological deterioration of storage wheat began with the root cap site, and then along the hypocotyls to germ direction, losing activity gradually.(2) Study on the respiration of wheat during physiological deterioration.Study on the respiration of wheat at different storage temperatures, the results showed that, the respiration of wheat at the beginning stage after water regulation increased gradually, the accumulation of CO2 concentration increased gradually. With the extension of storage time, the respiration decreased gradually at every storage temperature, the rate of CO2 concentration slowed down gradually, remained stable at last. At 50℃, the rate of respiration and CO2 accumulation were higher than 30℃ and 40℃ in a relatively short period of time, but the respiration of wheat nearly stopped after storing 6 weeks at 50℃, high temperature above 40℃ can speed up the process of stored wheat physiological deterioration.(3) Study on the physiological enzymatic activity during wheat physiological deterioration.The activity of dehydrogenase and amylase increased gradually at the beginning stage of storage, then decreased gradually at 30℃,40℃ and 50℃. The activity of CAT decreased gradually, finally maintained at a lower level. With the same moisture, at 50℃, the rate of enzyme activity changes was the fastest, the slowest at 30℃. It means that the storage temperature effected the change of physiological enzyme activity of wheat greatly.(4) Changes of RNase activity and structure of starch granules during wheat physiological deterioration.At different storage temperatures, the activity of RNase increased gradually at the beginning stage of wheat storage. After storing 3 moths, 2 months and 3 weeks at 30℃,40℃ and 50℃, the activity of RNase decreased gradually, finally maintained at a lower level. The activity of RNase changed fastest at the 50℃ condition among 3 storage temperatures. With the extension of storage time, the weight of large starch granules decreased gradually, kept in steady state at last stage of wheat storage. Weight of small starch granules decreased slightly at the high temperature environment of 50℃, weight changed little at 30℃,40℃. The ratio of spherical large starch granules in the general decreased, the ratio of ellipsoid large starch granules in the general increased gradually during wheat storage. The small starch granules were spherical at the beginning stage of wheat storage, then, the ratio of irregular shape small starch granules in the general increased.This paper further explores the influence factors on physiological deterioration of wheat storage, in order to determine the characteristics of storage wheat physiological deterioration, providing the reference to further clarify the mechanism of physiological deterioration safe storage and breeding of wheat.