Influence of low air humidity and low root temperature on water uptake, growth and aquaporin expression in rice plants.
The effects of low air humidity and low root temperature (LRT) on water uptake, growth and aquaporin gene expression were investigated in rice plants. The daily transpiration of the plants grown at low humidity was 1.5- to 2-fold higher than that at high humidity. LRT at 13°C reduced transpiration, and the extent was larger at lower humidity. LRT also reduced total dry matter production and leaf area expansion, and the extent was again larger at lower humidity. These observations suggest that the suppression of plant growth by LRT is associated with water stress due to decreased water uptake ability of the root. On the other hand, the net assimilation rate was not affected by low humidity and LRT, and water use efficiency was larger for LRT. We found that low humidity induced coordinated up-regulation of many PIP and TIP aquaporin genes in both the leaves and the roots. Expression levels of two root-specific aquaporin genes, OsPIP2;4 and OsPIP2;5, were increased significantly after 6 and 13 d of LRT exposure. Taken together, we discuss the possibility that aquaporins are part of an integrated response of this crop to low air humidity and LRT.
National Institute for Agro-environmental Sciences, Agro-Meteorology Division, Tsukuba, 305-8604 Japan.
Tsuneo
T
Kuwagata
Junko
J
Ishikawa-Sakurai
Hidehiro
H
Hayashi
Kiyoshi
K
Nagasuga
Keiko
K
Fukushi
Arifa
A
Ahamed
Katsuko
K
Takasugi
Maki
M
Katsuhara
Mari
M
Murai-Hatano
D020346:Aquaporins / Q000235:genetics* / Q000378:metabolism; D003080:Cold Temperature; D018506:Gene Expression Regulation, Plant; D006813:Humidity; D008565:Membrane Proteins / Q000235:genetics; D012275:Oryza / Q000254:growth & development / Q000502:physiology*; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology*; D036226:Seedlings / Q000235:genetics / Q000254:growth & development; D014867:Water / Q000378:metabolism
D020346:Aquaporins; D008565:Membrane Proteins; C491679:PIP2a protein, Oryza sativa; D010940:Plant Proteins; D014867:Water