Water-use efficiency and nitrogen uptake in rice seedlings grown under different light quality

Rice (Oryza sativa L.) cultivars ‘Taichung shen 10’ (‘TCS10’) and ‘IR1552’ were hydroponically grown under different light conditions to investigate the effect of light quality on their biomass, transpiration, water-use efficiency (WUE), carbon isotope discrimination (Δ), seed nitrogen (N) contribution and nitrogen uptake ability from the hydroponic nutrient solutions. Light emitting diode (LED) lighting systems were used to control light quality. Different light treatments were applied to the rice seedlings including red (R), green (G), and blue light (B), with red + blue light (RB) as control. The photon flux density was set at 105 μmol m-2 s-1. WUE and Δ were combined to evaluate whole-plant WUE. Improved whole-plant WUE was observed for both cultivars under R and RB light due to lower transpiration rates than under B light. Green light also improved Δ in both rice seedling cultivars. Seed N contribution of both cultivars was stable across all light treatments, while improved N uptake ability was observed under B and RB light. In addition, N uptake in ‘IR1552’ rice seedling cultivars did not respond as favourably to green light as ‘TCS10’ cultivars.