Effect of leaf aging on the photosynthetic capacity of F1 hybrid rice, Shanyou 63
1997
Hirao, K. (Kyushu Univ., Fukuoka (Japan). Faculty of Agriculture) | Kubota, F. | Saitou, K. | Obu, A. | Agata, W.
Top-expanded leaves are used to know the highest capacity of leaf photosynthesis in rice plant, and the plant photosynthetic capacity has been evaluated by the top-expanded leaf photosynthesis in many reports. However, the top leaf position is soon replaced by a new-expanding leaf, and most of the leaves of a plant are composed of aged ones. Hence, the photosynthetic rate and other physiological roles of aged-lower leaves become important points for more precise evaluation of plant photosynthetic capacity. In this study, as an experimental material, F1 hybrid rice cultivar, Shanyou 63 (SH), was used and grown in solution culture together with Japanese rice cultivar, Nipponbare (NI). Leaf aging was accelerated by growing these cultivars in solution of low nitrogen concentration for two weeks. The effects of the aging treatment on the photosynthesis of top-expanded and aged-lower leaves were compared between SH and NI. The results obtained are as follows: (1) SPC (soluble protein content) in leaves of SH was lower than that of NI. In particular, SPC in aged-lower leaf of SH greatly decreed by the low N treatment, and this fact may suggest that soluble protein in aged-lower leaves was more quickly decomposed in SH. (2) In leaves of the plants grown in the low N solution, no difference was detected in CER (CO2 exchange rate) between these two cultivars. The photosynthetic efficiency in SPC (CER per unit SPC) was higher in SH than in Ni. (3) It may be suggested that soluble protein decomposed in aged-lower leaves of SH is readily exported to a new-expanding leaf, by which the top-expanded leaves of SH are allowed to maintain relatively high photosynthetic level
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