| This research was conducted in both filed and laboratory with two hybrids edan 12 (with short hick ears) and edan 19(with long-thin ears) in 1999 and 2000 in order to study the physiological activities and seed-set capacity of summer-maize (zea mays L.) silks. Physiological characters of silks including the activity of superoxide dismutase (SOD),peroxidase (POD), succinic dehydrogenase and catalase (CAT), malondialdehyde (MDA) content, pH value, and water potential were measured during the growth, development and senescence of silks. Correlation of physiological characters and seed-set capacity of silks, viability of pollen grains and its relations to seed-set capacity, and the synchronization of pollen shedding with silking were also analyzed. The results showed that the seed-set capacity of silks remained higher during the first I Odays after silking and decreased rapidly after that time, silks lost their seed-set capacity about the 18th day after silking. Seed weight was also decreased as the pollination delayed. The activity of SOD and succnic dehydrogenase increased as the growth, development of silks and a peak appeared at the 10th day after silking, and decreased rapidly when the senescence of the silks started. The activity of enzymes especially the SOD was highly correlated with the seed-set capacity of silks. The MDA content increased during the early growth of the silks and decreased rapidly from 4th to 10th day after silking when the seed- set capacity of silks was much higher, the content of MDA was again increased slowly after that time during the senescence of silks. Correlation coefficient between MDA content and SOD activity was highly positive before the 4 days after silking, and significantly negative during the senescence of silks. No variation of POD activity was found before the 6th day after silking and increased rapidly after that time. The activity of CAT decreased after the appearance of silks on the cob and remained a relatively low level after the 5th day of silking. Correlation coefficient of seed-set capacity with the activity of POD was negative significantly, and was positive with the activity of CAT. The pH value of silks remained a relatively higher level before the 6th day and decreased dramatically from the 6th to 10th day after silking. An increment of pH value was observed when silks statied senescence, which might be caused by the decomposition of organic substances within the silks. The result indicated that higher pH levels of silks would be favorable to the fertilization and seed-set capacity and lower p1-I levels of silks would decrease the seed-set capacity. Water potential of silks increased slowly and decreased rapidly after reached to the peak at the 6th day after silking. Seed-set capacity was higher when water potential of silks remained from -0. lto - 0.3 MPa. Seed-set capacity of silks remained higher when pollinated with pollen grains shedding from the first 4 days and decreased rapidly with pollen grains shedding after that time. Seed weight was also higher when pollinated with pollen grains shedding from earlier days. Physiological activities of pollen grains, which represented by the activity of TTC, percentage of pollen grains germinated and the length of pollen tubes after 3 hours of culturing, was higher when shedding from earlier days, while Maturity of pollen grains was increased as the shedding time was delayed. Two peaks of TTC activity were observed during the daytime (11:00 and 17:00) and it was greater in the morning. Two types of synchronization bet... |
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