Phytochrome A deficiency improves nutrient ion uptake and productivity in rice ( <i>Oryza sativa</i> L.)

Photoreceptors perceive light to assist plants to adapt to diurnal changes under varying environmental conditions. Among them, phytochromes act as photoreceptors for red or far-red light, regulating numerous developmental processes in plants; however, their roles in nutrient ion uptake remain largely unexplored. In this study, we investigated the effect of phytochrome A (phyA) deficiency on nutrient ion uptake and photosynthetic activity in wild-type (WT) plants and phyA-deficient mutants (phyA mutants) grown hydroponically, and productivity of mature plants in paddy fields in rice (Oryza sativa L.). We found that the uptake of various nutrient ions and photosynthetic CO₂ assimilation increased in phyA mutants grown hydroponically with abundant nutrients. Moreover, grain and shoot dry weights were improved in phyA mutants grown in a paddy field under doubled fertilizer amounts in comparison with the recommended doses for WT plants. Quantification of mineral nutrients in grains revealed no difference in mineral nutrient content between WT plants and phyA mutants, despite phyA mutants showing increased grain weight per plant. Taken together, these results indicate that phyA mutants possess favourable agronomic traits that enhance productivity through improved nutrient utilization.