| Gansu He xi corn seed production area is the country's largest production base, annual corn seed production area of more than 1.2 million hm2, accounting for the national corn with 60% of the volume, ensure the seed quality and safety of national food security has important strategic significance. High vigor seed has the advantage of high growth and productive potential. It is the basis of high yield. It is very important to improve the quality of seed. But the research on seed vigor of maize is still inadequate, especially according to the maximum dry matter, grain moisture, line of dairy development, maturity of judgment of seed vigor and resistance to cold and other indicators, seed production base in Gansu reported rare. He xi District Seed early frost appeared earlier and short frost free period, to determine the optimal harvest time, avoid the influence of early autumn frost and cold and other adverse climate, to ensure the He xi seed production base of corn seed quality has important significance. Main conclusions are as follows:1. There was a significant difference in seed moisture and 100-seed weight of Maize Hybrids in different harvest time. XY335, ZD958, JX1 grain moisture and different harvest period decreased linearly, 100-seed weight and different harvest time increased linearly, 100-seed weight and grain moisture is linear decline. Grain moisture of XY335 at 32 d after pollination reached 61.62%, 100-seed weight 11.23g; grain moisture of JX1 71.57%, 100-seed weight 10.45g; grain moisture of ZD958 69.28%, 100-seed weight 11.53 g. At 70 d after pollination, grain moisture of 3 Hybrid seeds are reduced to 35.37%(XY335), 40.68%(JX1), 38.06%(ZD958), 100-seed weight increased to 33.43 g, 36.16 g, 34.49 g, the dehydration rate of ZD958> JX1 > XY335, 100-seed weight of the rate of increase in the number of JX1> ZD958> XY335.2. Different harvest period has great influence on the seed vigor of Maize Hybrids. At 43 d after pollination, the standard germination reached more than 84.9%, and germination remained between 87.6%-92.4% in late grain filling. At 64 d after pollination, the germination reached the maximum of 92.4%, while the seed moisture was 41.83% and 100-seed weight was 32.95 g. Due to stress cold-test and cool-test by temperature, the seed vigor in the whole filling stage is generally lower than standard germination test, the germination increased slowly in the early filling stage and the degree of reducing advanced in the late filling stage, the cool-test germination influenced by temperature is greater, maximum in cold-test and cool-test germination at 58-61 d after pollination reached respectively 81.3% ? 76.7%.The aging of germination was similar to field emergence rate, reached a maximum at 58 d after pollination, respectively85.3%(field emergence rate)?82.6%(aging of germination), so the harvest date can be advanced to avoid early frost damage. At 43-67 d after pollination average field emergence rate of 81.4%, is 1.07 times the cold-test(76%) and 1.13 times cool-test(72.1%). Standard germination of 31.3% at 32 d after pollination was significantly more than 17.5% that of the field emergence rate, but before 43 d pollination growth rate is lower than field emergence rate. With the increase of days after pollination, late standard germination is always higher than the field emergence rate, approximately 1.09 times. Therefore, germination rate and vigor of the biggest harvest XY335 began to 50 days after pollination, ZD958 and JX1 pollination after 58 days, than the current production and harvest early 10 d. At this time about 40% of grain moisture, avoid the influence of early frost damage of corn seed quality.3. The effect of seed maturity on the activity of enzymes was different. With the increase of maturity, seed growth accelerated the demand for oxygen increasing, so that the oxygen partial pressure decreased, leading to seed internal SOD activity showed a reduction in volatility trend. At 43-49 d after pollination SOD activity reached the highest. POD activity increased with the increase of maturity. The difference was obvious in different harvest times, and at 67 d after pollination POD activity was the highest, then began to decrease. There was no significant difference in the activity of dehydrogenase in different harvest time, but the activity of dehydrogenase was relatively higher in the later stage of harvest, but there were differences among different varieties. A-amylase activity show a first increased and then reduced trend with the increase of maturity, but there was no obvious difference in the different maturity. The a-amylase activity reached the maximum at 49-52 d after pollination, and then gradually decreased. A-amylase activity differences in different maturity had no significant difference, which in 49-52 d after pollination a- amylase activity reached the maximum, then began to decrease. There are significant differences in different Species of a-amylase activity. Finally in the whole harvest period, the a-amylase activity of XY335 was highest, followed by JX1, ZD958 was the lowest.4. The reduction rate of electrical conductivity at 32-49 d was fast, and decreased by 0.92 us/(cm·g-1)/d per day, but in the late filling stage the decrease rate was only 0.08 us/(cm·g-1)/d, basically stable. MDA content in the whole of the harvesting period decreased, days after pollination and the content of MDA into the logarithmic decrement relationship. At late filling stage, the content of MDA continued to decrease, indicating that at this time there was the peroxidation of membrane lipid.5. The field emergence rate of Maize Hybrid seeds was significantly different at different harvest time, and the rate of field emergence was a part of the external performance of seed vigor. The field emergence rate of XY335 at 32 d after pollination reached 23.2%, while JX1 and ZD958 were close to 14.9% and 14.3% respectively. With the increase of maturity, the field emergence rate of XY335 at 43 d after pollination reached more than 80%, and the maximum was 93.3% in the 58 d. The field emergence rate of JX1 at 58 d after pollination reached the maximum 88.5%, the late decreasing rate is slow. The field emergence rate of ZD958 was the lowest, the average field emergence rate of at 46-70 d after pollination reached 75.3%, and the maximum germination rate is 83.7% when the harvest is pushed around 10 d, to meet the early frost damage probability, but for XY335 and JX1, probability of meeting early frost was small. |
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