Nitrogen partitioning in the photosynthetic apparatus of Plantago asiatica leaves grown under different temperature and light conditions: similarities and differences between temperature and light acclimation.

Effects of growth temperature and irradiance on nitrogen partitioning among photosynthetic components were studied. Plantago asiatica was grown under different temperature and light conditions. Growth conditions were regulated such that the Chl a/b ratio in leaves grown at a low temperature with a low irradiance was similar to that in leaves grown at a high temperature with a high irradiance, suggesting that the balance between acquisition and utilization of light energy in the photosynthetic apparatus was similar between the two growth conditions. When plotted against the leaf nitrogen content, the RuBP (ribulose-1,5-bisphosphate) carboxylase content did not significantly differ depending on growth conditions. Both high irradiance and low temperature decreased nitrogen partitioning to Chl-protein complexes. Low temperature increased nitrogen allocation to stroma FBPase (fructose-1,6-phosphatase) irrespective of growth irradiance. Gas exchange measurement indicated that the ratio of the electron transport (J(max)) to the maximum carboxylation rate (V(cmax)) was not affected by growth irradiance but by growth temperature. It is concluded that nitrogen partitioning between acquisition and utilization of light energy responds to both growth temperature and irradiance, while nitrogen partitioning between carboxylation and regeneration of RuBP responds only to growth temperature.