Abstract
The leaves of rice seedlings (Akitakomachi) show severe visible injury after a few days chilling (10°C) only when the roots were not chilled and kept at 25°C (L/H), whereas no such injury is observed when the whole seedlings were chilled at 10°C (L/L). This High-Root-Temperature-induced (HRT) chilling injury is observed only in the presence of nitrate in the nutrient solution, and is preceded by the blockage of photosynthetic election transport between PSII and PSI, and cyclic electron transport of PSI. In order to help figure out the relationship between nitrate and the malfunction of photosynthesis, we compared the time-dependent changes in the major inorganic ions, using nitrate-starved seedlings that are transferred to new nutrient solution at the beginning of the treatments. We found the severer injury in the nitrate-starved seedlings, and the rapid nitrate accumulation in the roots and leaves of the L/H seedlings; several hold higher in the leaves than those at 25°C in the treatments shorter than 12h. Nitrite was detected only in the L/H leaves during two days of treatments. We will also show some new findings on photosynthetic characteristics.
