Response of photosynthetic pigments, gas exchange and chlorophyll fluorescence parameters to light quality in Phoebe bournei seedlings

Abstract

To reveal responses of photosynthetic physiological characteristics in Phoebe bournei seedlings to different light qualities and provide a basis for light environment regulation in seedling cultivation and under-canopy regeneration, we analyzed the photosynthetic physiological characteristics of P. bournei seedlings under five types of light qualities (white, red, blue, green, red: blue = 1:1) with the same photosynthetic photon flux density of 100 ± 5 μmol·m⁻²·s⁻¹. The results showed that blue light significantly promoted chlorophyll content, Rubisco, RCA and photosynthetic rate (Pn), but water use efficiency (WUE) was reduced by blue light. The red light treatment exhibited the highest initial fluorescence (Fo), but wasn't conducive to the accumulation of photosynthetic pigments and had the lowest maximum photochemical efficiency (Fv/Fm) and potential photochemical efficiency (Fv/Fo). The seedlings treated by green light showed the lowest Pn, Tr, WUE, rubisco, with the highest Fv/Fm and Fv/Fo. Red-blue light significantly increased WUE, photosynthetic electron transfer rate (ETR), actual photosynthetic efficiency Y(II), and quantum yield of regulated energy dissipation Y(NPQ) in PSII of P. bournei seedlings, with the second highest Pn across treatments. In conclusion, the effects of single light quality on photosynthetic characteristics of P. bournei seedlings exhibited both advantages and disadvantages. The combination of red and blue light, which integrated the advantages of single light quality, enhanced the photosynthetic performance and photoprotective ability of P. bournei seedlings. It promoted the energy conversion and utilization efficiency of PSII, resulting in the best carbon assimilation efficiency. Therefore, red-blue light promoted the growth and development of Phoebe bournei seedlings.