The mesophyll anatomy enhancing CO2 diffusion is a key trait for improving rice photosynthesis.
Increases in rates of individual leaf photosynthesis (P(n)) are critical for future increases in yields of rice plants. Although many efforts have been made to improve rice P(n) with transgenic technology, the desired increases in P(n) have not yet been achieved. Two rice lines with extremely high values of P(n) 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 P(n) values of the two lines at an ambient CO(2) concentration of 370μmol mol(-1) as well as at a saturating concentration of CO(2) 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 CO(2) 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 P(n) significantly, both at the current atmospheric concentration of CO(2) and at the increased concentration of CO(2) expected in the future, using appropriate combinations of genetic resources that are available at present.
Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan.
Shunsuke
S
Adachi
Toru
T
Nakae
Masaki
M
Uchida
Kazuya
K
Soda
Toshiyuki
T
Takai
Takao
T
Oi
Toshio
T
Yamamoto
Taiichiro
T
Ookawa
Hiroshi
H
Miyake
Masahiro
M
Yano
Tadashi
T
Hirasawa
D002245:Carbon Dioxide / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D004058:Diffusion; D004579:Electron Transport; D004789:Enzyme Activation; D007178:Inbreeding; D058503:Mesophyll Cells / Q000378:metabolism / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission; D009584:Nitrogen / Q000378:metabolism; D012275:Oryza / Q000033:anatomy & histology / Q000201:enzymology / Q000502:physiology*; D010788:Photosynthesis; D018515:Plant Leaves / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism
D002734:Chlorophyll; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D009584:Nitrogen