Effects of short light/dark cycles on photosynthetic pathway switching and growth of medicinal Dendrobium officinale in aeroponic cultivation

Abstract

<i>Dendrobium officinale</i> has high medicinal value but grows slowly in natural environment due to its special CAM photosynthetic pathway. In this study, <i>D. officinale were grown aeroponically</i> with light/dark cycles of 12 h/12 h, 4 h/4 h, and 2 h/2 h for 150 d. The photosynthetic electron transfer characteristics, photosynthetic CO₂ fixation pathways, and accumulations of biomass and soluble polysaccharides in <i>D. officinale</i> leaves were studied. The results showed that the photosynthetic apparatus states of <i>D. officinale</i> in aeroponic cultivation under short light/dark cycles of 4 h/4 h and 2 h/2 h were better than that under 12 h/12 h. The dark net CO₂ exchange percentages of <i>D. officinale</i> were negative in short light/dark cycles of 4 h/4 h and 2 h/2 h, and the daily net CO₂ exchange amount and dry/fresh weight increases were doubled compared with those in 12 h/12 h light/dark cycle. High soluble polysaccharides content and the soluble polysaccharides yield of <i>D. officinale</i> were obtained in the shorter light/dark cycle of 2 h/2 h. Therefore, the photosynthetic pathway of <i>D. officinale</i> could be switched from CAM to C3 by short light/dark cycles of 4 h/4 h and 2 h/2 h, and its higher biomass accumulation and soluble polysaccharides yield could be obtained by the shorter light/dark cycle of 2 h/2 h in aeroponic cultivation.