Response of photosynthetic capacity of tomato leaves to different LED light wavelength

Abstract Light-emitting diodes (LEDs) are widely used in horticultural facilities in recent years. However, the influence of light quality on photosynthesis still calls for further exploration. This study comprehensively analyzed the influence of different LED lighting (white: W, combination of red and blue 1:1: RB, blue: B, purple: P and red: R) on photosynthetic electron transport in tomato leaves. Plant height under B and P treatments was significantly higher than the other treatments and showed more compact development. Photosynthetic pigment content and net photosynthetic rate (Pn) of B and P treatments were significantly lower than the W treatment. The redox state of photosystem I was repressed by blue and purple light while the intrinsic PSII activity was not altered by the treatments. The ETR (II) and ETR (I) under B and P treatment were lower than the other treatments, while the cyclic electron flow (CEF), the quantum yield of regulated energy dissipation in PSII [Y(NPQ)] and the quantum yield of PSI non-photochemical energy dissipation due to the donor-side limitation [Y(ND)] were higher, indicating that B and P treatment induced non-photochemical quenching of PSII and excitation of PSI’s self-protection mechanisms in tomato plants. Blue and purple light exposure resulted in a higher proton gradient (ΔpH), leading to impaired thylakoid membrane integrity and inhibited the activity of ATP-synthase. In conclusion, the blue and purple light significantly reduced photosynthesis efficiency, enhancing CEF and inducing NPQ for photoprotection of PSII and PSI via lumen acidification.