Chlorophyll a Fluorescence in 20 Plant Species of Dendrobium

Dendrobium is one of the largest genera in the Orchidaceae family. The photosynthetic characteristics in some Dendrobium species have been made separately, but few studies have focused on the difference in chlorophyll a fluorescence across Dendrobium species, especially in the same environment. The actual photochemical efficiency (ΔF/Fm'), non-photochemical quenching (NPQ), electron transport rate (ETR), energy partitioning and the rapid light response curves were measured in 20 Dendrobium species radiated by different light intensity. D.officinale, D.aurantiacum, D.dixanthum, D.fimbriatum, D.loddigesii, D.brymerianum, D.nobile, D.capillipes, D.crepidatum, D.findlayanum, D.harveyanum, D.thyrsiflorum, D.chrysotoxum, D.trantuanii, D.farmer and D.pulchellum had higher ΔF/Fm' in low light condition. Under low light condition, NPQ in all 20 Dendrobium species were relative low, but when PAR arrive at 200 μmol/(m2·s), NPQ in the 20 species rise sharply, and then gradually tend to be stable.D. loddigesii and D.chrysotoxum possess high value of ETR, while D.officinale display low value of ETR. Light energy was mainly used for photosynthesis in low light environment. With the increase in light intensity, light energy allocated to heat dissipation increased gradually. Based on the results obtained here, different shading levels should be selected according to different light response ability of Dendrobium species in the artificial cultivation.