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Effects of waterolgging on the growth and development of sorghum
而百粒重之減少為其次。淹水處理導致植株 CGR、NAR 和
The experiments were conducted to explore the responses of sorghum plants (Sorghum bicolor L.) to waterlogging. Hybrid sorghum cultivar Taichung 5 was used as plant materials. The four items have been conducted including seedling emergence res- ponses, sensitive stage determination, leaf growth and grain filling responses. And the results will be discussed in aspects of source-sink relationship and translocation of assimilates. Seedling emergence was significantly inhibited by waterlogging performed at 3-hour after sowing, and it was inhibited severely at 24-hour after sowing. Emergence percentage, seedling percentage, emergence coefficent, seedling height and seedling dry weight were all decreased significantly. It was probably due to the vigorously enzymatic activity in seed within 24-hour after sowing and the increa- sed water uptake, cell membrane breakage, electro- lyte leakage and internal solute lose of seeds as seeds subjected to waterlogging. The ATP generation in seeds was declined under anoxia, resulted in a decrease of physiological activities, and the seed- ling emergence was severely reduced ultimately. Dry matter accumulation and grain yield were significantly decreased when the sorghum plant were subjected to waterlogging for 5-day. The most sen- sitive stage to waterlogging was booting stage, grain yield was significantly decreased about 50%, mainly due to the decrease of grain number of pani- cle per whorl, and such decrease occurred at the lower grain position was more obvious, the reduction of 100-grain weight was lesser. The reduction of yield was closely related to lower source potential and sink potential, which was mainly derivated from the reduction of crop growth rate (CGR), net assi- milation rate (NAR), and panicle filling rate (PFR), but the leaf area duration (LAD) and panicle effec- tive filling duration (PEFD) were not affected by waterlogging. The leaf growth was also inhibited as sorghum plants subjected to 5-day waterlogging, leaf CO2 exchange rate, Rubisco activity, and chlorophyll content were all declined, resulting in the decrease of the CO2 fixation ability. The reduction of accu- mulation of sucrose and glucose in leaf were also observed. In addition, the leaf water potential was reduced and the osmotic adjustment was observed significantly by waterlogging. However, the enzy- matic activies of sucrose metabolism and starch synthesis in leaf were not significantly inhibited by waterlogging. Although the reduction of grain yield occurred uneer the waterlogging, the severe decrease of grain number resulted in no changes in single grain weight of panicle per whorl. Consequently, the enzymatic activies of sucrose metabolism and starch synthesis in single grain were not directly affected by water- logging, and sucrose, glucose, and starch contents in grain were also unaffected by waterlogging. After a 5-day waterlogging at booting stage, the ATP content and energy charge of the flag leaf were lowered significantly. The results indicated that energy deficiency could not be enough to maintain physiological activity of the flag leaf. Also the decreasing tendency of energy charge of the upper culm after drainage might suggested that ability of photosynthate translocation were inhibited. In addi- tion, the pathway of photosynthate translocation from flag leaf to panicle might be blocked.
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