Effects of Light Quality on the Growth, Development and Metabolism of Rice Seedlings (Oryza sativa L.)

The V3 seedlings of two rice cultivars, IR1552 (purple leaf) and Taichung sen 10 (TS10, green leaf) were hydroponically cultured under 12 h photoperiod at 30/25 degrees C (day/night), 70% relative humidity and 160 mu mol m(-2)s(-1) photon flux density under red light-emitting diodes (LEDs) (R), green LEDs (G), blue LEDs (B) and red + blue LEDs (RB) inside growth chambers for 14 days (starting 2 days after sowing). The results showed that shoot elongation was induced under the exposure of R and G. The maximum health index [(stem diameter/plant height) x biomass)] occurred under B because blue light inhibited shoot elongation. The root length under RB was the shortest. Different wavelengths mediated the chlorophyll (Chl) a/b ratio of the leaves. The content of anthocyanin (Ant) in seedling leaves was observed to be highest in RB but less in R and B, the latter pair being even lower than in G. B light LEDs enhanced effective quantum yield of PSII photochemistry (Phi(PSII)) and photochemical quenching (q(P)), but reduced non-photochemical quenching (NPQ) of seedling leaves. B LEDs also showed higher total protein content in the tested leaves compared to B plus R. In summary, precise management of irradiance and wavelength may hold promise in maximizing the economic efficiency of plant growth, development and metabolic potential of rice seedlings grown in controlled environments.