Carbon and Nitrogen Transport during Grain Filling in Rice Under High-temperature Conditions |
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| Authors: | S Ito T Hara Y Kawanami T Watanabe K Thiraporn N Ohtake K Sueyoshi T Mitsui T Fukuyama Y Takahashi T Sato A Sato & T Ohyama |
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| Institution: | Graduate School of Science and Technology, Niigata University, Niigata, Japan;
Faculty of Agriculture, Niigata University, Niigata, Japan;
Faculty of Bioresource Sciences, Akita Prefectural University, Akita, Akita, Japan |
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| Abstract: | Rice ( Oryza sativa cv. Koshihikari) seedlings were grown in a sandy dune soil in pots with a basal dressing of N (0.5 g N), P and K. Two N treatments were applied, a +N treatment in which a top dressing of 15N-labeled 0.5 g N was supplied on July 20 and a −N treatment in which no additional fertilizer was supplied. During the grain-filling stage from August 6 to 13, plants were subjected to one of three temperature treatments; controlled low temperature, LT (day/night 28/23 °C), controlled high temperature, HT (35/30 °C) and uncontrolled glasshouse temperature, UT (day/night averages, 38/26 °C). All plants were then exposed to 13CO2 for 1 h on August 11 in a growth chamber at 25 °C. On August 13, all plants were harvested and the 13C and 15N abundances and starch and sugar concentrations in the ears, shoots and roots were determined. The 13C content of the ear was lower in UT than in LT irrespective of the +N or −N treatment. The translocation of 15N to the ears was also slightly depressed in UT compared with LT. Under high-temperature conditions (HT and UT), the starch content per plant was reduced for −N, but for +N, it was not significantly different among the temperature treatments. A high accumulation of sucrose was observed in all plant parts under UT conditions. It is suggested that extreme high day temperatures during the grain-filling period may reduce starch synthesis in the grains and, especially so under N-deficient conditions. High temperatures also induce an accumulation of sucrose and a decrease in carbon and nitrogen transport from the shoots to the ears via the phloem. |
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| Keywords: | carbon high temperature nitrogen rice transport |
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