Influence Of Freezing Injury On Germination And Physiological-biochemical Changes In Different Grain Types Of Maize Seed

Seed of maize is the most basic means of production of agriculture, its security of producing affects its quality, thus affects agricultural production and food security, relating to the vital interests of farmers and practical benefits. Low-temperature damage in northern China is a vital environmental factor to impact security of seed production, from which seed is very easy to get hurt during harvest and storage, which happens very often in seed production bases of Hexi Corridor, Gansu province, and causes a certain amount of economic losses. The freshly harvested maize kernels of different grain type of Funongl, Zhengdan958, Liaodan565 were used in this research to measure their germination rate, germinability, seed vitality index, electrical conductivity, soluble sugar content and superoxide dismutase, peroxidase, amylase activity. The relationships of the indicators with variation of freezing resistance of different shapes of maize kernels were analyzed systematically. The results showed as following.1. The germination rate of maize kernels of different shapes decreased as the temperature decreasing, the germination rate of durum maize was higher at freezing injury than other shape of maize. The germination rate decreased with time longer at low-temperature. The freezing injury of maize of different types was positively related to water content, freezing injury temperature and time, which significantly affected germination rate, germination energy and germination index. The seed vigor of maize of these three different types changed significantly at-10℃. The germination rate of maize kernels decreased because of low-temperature damage when the temperature was under-10℃and water content above 15%-20%, and it the low temperature did not affected the germination rate of maize kernels when the temperature was above-10℃and water content below 15%-20% with germination rate and germination energy unaffected, SV and quality of seed unchanged. When the temperature was below-25℃, the germination rate, germination energy and germination index dropped to minimum.2. Freezing injury caused to membrane pore larger, a lot of leakage of intracellular ions, the conductivity increasing. The electrical conductivity was positively correlated to temperature and freezing time, significantly affected conductivity. With temperature lower and the freezing time longer, the conductivity was larger and the cell membrane system was damaged more seriously. The cell membrane of Funongl was damaged at lightest level, which indicated that durum type has a certain resistance to low temperature, relative stability of cell membrane structure, the best antifreezing capability. The anti-freezing capability of Liaodan565 was not very nice.3. Freezing injury caused imbalance and severe damage of the protective enzyme system of seed of different grain type. SOD and POD activity in maize seeds gradually increased, and the variation was not exactly the same. The changes of enzyme activity of low temperature resistant grain type were much more significant than that of low temperature non-resistant grain type. Enzyme activity was positively corelated to the temperature and freezing time. Single and multiple interactions affected enzyme activity significantly, which was possibly caused by the differences of resistance of maize of different grain type. POD activity and SOD activity of Durum-type seeds increased more significantly than those of the other two grain types, indicating that it has a strong resistance to low temperature.4. Treated with low temperature, the sugar content of maize seed of three grain types increased at different degrees and the trend of changes was similar. The accumulation of soluble sugar increased the cell osmotic pressure and water retention, so that materials within cells was hard to be frozen at low temperatures, intracellular metabolic activity kept normal, role resistant to low temperature was played. Seed soluble sugar content of maize of different grain type was positively related to temperature, freezing time and water, and correlation was significant. The higher soluble sugar content of maize seeds, the stronger resistance to low temperature and freezing capacity. Frost resistance strength was FunongNol>Zhengdan958>Liaodan565.5. Under low-temperature damage, the amylase activity of maize seeds was increased, and the starch accumulation was decreased. The factors of low-temperature and low-temperature duration had a significantly effect on amylase activity.