Changes in the photosynthesis properties and photoprotection capacity in rice ( Oryza sativa ) grown under red, blue, or white light

Non-photochemical quenching (NPQ) of the excited state of chlorophyll a is a major photoprotective mechanism plants utilize to survive under high light. Here, we report the impact of long-term light quality treatment on photosynthetic properties, especially NPQ in rice. We used three LED-based light regimes, i.e., red (648–672 nm), blue (438–460 nm), and “warm” white light (529–624 nm), with the incident photon flux density of 300 µmol photons m −2 s −1 , the difference in the absorbed photon flux densities by leaves grown under different light quality being less than 7%. Our results show that blue light, as compared to white light, induced a significant decrease in F v / F m , a decreased rate of reduction of P 700 + after P 700 was completely oxidized; furthermore, blue light also induced higher NPQ with an increased initial speed of NPQ induction, which corresponds to the qE component of NPQ, and a lower maximum quantum yield of PSII, i.e., Y(II). In contrast, rice grown under long-term red light showed decreased Y(II) and increased NPQ, but with no change in F v / F m . Furthermore, we found that rice grown under either blue or red light showed decreased transcript abundance of both catalase and ascorbate peroxidase, together with an increased H 2 O 2 content, as compared to rice grown under white light. All these data suggest that even under a moderate incident light level, rice grown under blue or red light led to compromised antioxidant system, which contributed to decreased quantum yield of photosystem II and increased NPQ.