Objective Light is a pivotal factor influencing rice growth and development. This study investigated the effects of different LED light quality ratios on rice growth and yield, aiming to identify optimal light formulas that can shorten the growth cycle while synergistically enhancing yield.

Method Using japonica rice 'Nipponbare' (Nip) and indica rice 'Wufeng B' (WFB) as experimental materials, control groups (CK) grown under outdoor natural conditions were established, different combinations of red, white, blue, and far-red LED light quality ratio (LQR) were set up in a plant factory to analyze their effects on rice morphological parameters, development processes and yield formation.

Result Different LED light quality ratios significantly influenced rice growth and yield formation. LQR3 (50%R : 50%W : 100%B : 100%FR) and LQR6 (100%R : 100%W : 100%B : 100%FR) treatments markedly promoted growth during both the basic vegetative and photoperiod-sensitive phases. The high-red-light treatment LQR1 (100%R : 0%W : 100%B : 100%FR) increased plant height and leaf length but reduced lodging resistance. In contrast, the high-blue-light treatment LQR5 (0%R : 100%W : 100%B : 100%FR) significantly suppressed plant height and tillering. During the basic vegetative phase, no significant differences in SPAD values were observed between treatments and CK in Nip, except for LQR1 which showed significantly lower values than other treatments. For WFB, no significant difference was observed between LQR5 and CK, but LQR5 exhibited the highest SPAD value, significantly exceeding other treatments. During the photoperiod-sensitive and heading phases, all treatments had significantly lower SPAD values than CK, with LQR3 maintaining the highest levels, indicating enhanced photosynthesis and transition from vegetative to reproductive growth. By the heading phase, Nip showed no significant differences in SPAD values among CK, LQR3 and LQR5 treatments, but these values were significantly higher than other treatments. WFB under high-blue-light conditions (LQR5) produced the highest SPAD values. All plant factory treatments significantly shortened the growth cycle. Correlation analysis showed that the correlation coefficient between Nip light quality ratio and heading date was -0.49, while WFB was only -0.10. Compared to CK, Nip showed the shortest heading time under LQR3 and LQR6 treatments, with total growth period reduced by 34.08% and 34.68%, and yield increased by 37.98% and 36.98%, respectively. For WFB, LQR5 resulted in the shortest heading time with a 42.40% reduction in total growth period, followed by LQR3 and LQR6 (37.69% and 37.99% reduction). Yield under LQR3 and LQR6 increased by 81.25% and 144.32% compared to CK. Principal component analysis of yield traits showed that LQR3 achieved the highest comprehensive scores for both Nip (0.57) and WFB (0.64), followed by LQR6 (0.51 for Nip and 0.59 for WFB).

Conclusion Nip and WFB achieved the shortest heading time under LQR6 and LQR5 conditions, respectively. Both LQR3 and LQR6 significantly shortened the growth cycle and enhanced yield in Nip and WFB.