Adaptation responses in C-4 photosynthesis of maize under salinity

作者：Omoto Eiji; Taniguchi Mitsutaka; Miyake Hiroshi^*

来源：Journal of Plant Physiology, 2012, 169(5): 469-477.

DOI：10.1016/j.jplph.2011.11.009

• C-4 photosynthesis
• Enzyme activity
• Maize
• NADP-ME type
• Salinity

The effect of salinity on C-4 photosynthesis was examined in leaves of maize, a NADP-malic enzyme (NADP-ME) type C-4 species. Potted plants with the fourth leaf blade fully developed were treated with 3% NaCl solution for 5 d. Under salt treatment, the activities of pyruvate orthophosphate dikinase (PPDK), phosphoenolpyruvate carboxylase (PEPCase). NADP-dependent malate dehydrogenase (NADP-MDH) and NAD-dependent malate dehydrogenase (NAD-MDH), which are derived mainly from mesophyll cells, increased, whereas those of NADP-ME and ribulose-1,5-bisphosphate carboxylase, which are derived mainly from bundle sheath cells (BSCs), decreased. Immunocytochemical studies by electron microscopy revealed that PPDK protein increased, while the content of ribulose-1,5-bisphosphate carboxylase/oxygenase protein decreased under salinity. In salt-treated plants, the photosynthetic metabolites malate, pyruvate and starch decreased by 40,89 and 81%, respectively. Gas-exchange analysis revealed that the net photosynthetic rate, the transpiration rate, stomatal conductance (g(s)) and the intercellular CO2 concentration decreased strongly in salt-treated plants. The carbon isotope ratio (delta C-13) in these plants was significantly lower than that in control. These findings suggest that the decrease in photosynthetic metabolites under salinity was induced by a reduction in gas-exchange. Moreover, in addition to the decrease in gs, the decrease in enzyme activities in BSCs was responsible for the decline of C-4 photosynthesis. The increase of PPDK, PEPCase, NADP-MDH, and NAD-MDH activities and the decrease of NADP-ME activity are interpreted as adaptation responses to salinity.

• 出版日期2012-3-15