Comparison of reconstruction of photosynthesized 14C compounds incorporated into shoot between rice and soybean

Abstract

This study deals with the processes whereby the 14C-compounds, which have been constructed in shoot by 14CO2 fixation during the vegetative growth stage, maximum shoot growth (MSG) stage, and mid-ripening stage, were respired by shoot or other organs and reconstructed in other organs and into other compounds during the growth of rice and soybean. Results are as follows. 1. 14C once incorporated into leaves, stems, and roots at the vegetative growth stage was largely respired by the MSG stage in soybean, and during ripening in rice. In soybean a large amount of l4C which had been incorporated into plant at the MSG stage and mid-ripening stage was also respired by harvest, unlike in rice. Thus, soybean immediately respired l4C compounds once they were incorporated into plant during growth, whereas rice respired a relatively small amount of l4C before the ripening stage and stored l4C compounds in shoot, then respired them after the MSG stage. 2. l4C once incorporated into carbohydrates of leaves at each stage was reconstructed in larger amounts in soybean than in rice. 3. l4C once incorporated into protein in leaves and carbohydrate in shoot at vegetative growth stage was largely reconstructed by the MSG stage in soybean, and during ripening in rice. 4. Nitrogen which had been accumulated in shoot until the MSG stage was actively retranslocated to harvesting organs in soybean but not in rice. Based on these results, it is concluded that soybean could actively remetab-olize carbon and nitrogen compounds once these were incorporated into leaves and stems, whereas the remetabolization of carbon and nitrogen compounds was relatively limited in rice. © 1991 Taylor & Francis Group, LLC.