mesophyll anatomy enhancing CO2 diffusion is a key trait for improving rice photosynthesis

• Published in: Journal of experimental botany 2013-02, Vol.64 (4), p.1061-1072
• Main Authors: Adachi, Shunsuke, Nakae, Toru, Uchida, Masaki, Soda, Kazuya, Takai, Toshiyuki, Oi, Takao, Yamamoto, Toshio, Ookawa, Taiichiro, Miyake, Hiroshi, Yano, Masahiro, Hirasawa, Tadashi
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; carbon dioxide; Carbon Dioxide - metabolism; Chlorophyll - metabolism; crop yield; Diffusion; electron transfer; Electron Transport; Enzyme Activation; Fundamental and applied biological sciences. Psychology; genetically modified organisms; inbred lines; Inbreeding; leaves; mesophyll; Mesophyll Cells - metabolism; Mesophyll Cells - ultrastructure; Microscopy, Electron, Transmission; Nitrogen - metabolism; nitrogen content; Oryza - anatomy & histology; Oryza - enzymology; Oryza - physiology; Photosynthesis; plant growth; Plant Leaves - enzymology; Plant Leaves - physiology; Plant Leaves - ultrastructure; Plant physiology and development; ribulose-bisphosphate carboxylase; Ribulose-Bisphosphate Carboxylase - metabolism; rice
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/ers382

Increases in rates of individual leaf photosynthesis (Pn) are critical for future increases in yields of rice plants. Although many efforts have been made to improve rice Pn with transgenic technology, the desired increases in Pn have not yet been achieved. Two rice lines with extremely high values of Pn were identified among the backcrossed inbred lines derived from the indica variety Takanari, one of the most productive varieties in Japan, and the elite japonica variety Koshihikari (Koshihikari/Takanari//Takanari). The Pn values of the two lines at an ambient CO2 concentration of 370μmol mol–1 as well as at a saturating concentration of CO2 were 20–50% higher than those of the parental varieties. Compared with Takanari, these lines had neither a higher content nor a higher activity of ribulose 1,5-bisphosphate carboxylase/oxygenase when the leaf nitrogen contents were similar, but they did have high mesophyll conductance with respect to CO2 flux due to their higher density and more highly developed lobes of mesophyll cells. These lines also had higher electron transport rates. The plant growth rates of these lines were higher than that of Takanari. The findings show that it is possible to increase Pn significantly, both at the current atmospheric concentration of CO2 and at the increased concentration of CO2 expected in the future, using appropriate combinations of genetic resources that are available at present.