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

Abstract

Dendrobium officinale has high medicinal value but grows slowly in natural environment due to its special CAM photosynthetic pathway. In this study, D. officinale were grown aeroponically 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 CO 2 fixation pathways, and accumulations of biomass and soluble polysaccharides in D. officinale leaves were studied. The results showed that the photosynthetic apparatus states of D. officinale 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 CO 2 exchange percentages of D. officinale were negative in short light/dark cycles of 4 h/4 h and 2 h/2 h, and the daily net CO 2 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 D. officinale were obtained in the shorter light/dark cycle of 2 h/2 h. Therefore, the photosynthetic pathway of D. officinale 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.

Effects of Extended Light/Dark Cycles on Solanaceae Plants

“…Among various environmental factors, light has been found to be one of the most important variables affecting phytochemical concentrations in plants [ 29 , 30 ]. While it is widely understood that light intensity [ 31 , 32 ], photoperiod [ 32 , 33 , 34 , 35 , 36 , 37 ], and spectral composition of light [ 32 , 38 , 39 , 40 ] have significant effects on the nutritional value of plants, this research and few previous studies [ 9 , 12 , 13 , 14 , 15 , 16 , 17 , 41 ] have shown that unconventional light distribution in time as an independent variable may also significantly affect plant nutritional value. Accumulation of substances with antioxidant properties improves plant nutritional value and makes the product beneficial to health and more competitive.…”

“…So far, related studies have mainly focused on light intensity, photoperiod, daily light integral (DLI), and light quality. There are few reports [ 9 , 12 , 13 , 14 , 15 , 16 , 17 ] on the effects of intermittent light, i.e., abnormal light/dark cycles on plant growth and phytochemical content of lettuce, sweet potato, microgreens, Coffea arabica and Dendrobium officinale . They demonstrated that different abnormal light/dark cycles are beneficial for crop production and have the potential to reduce energy consumption by optimizing yield or other targeted traits.…”

“…The stimulating effect of unconventional irradiation modes on growth is partially attributed to their positive regulation of photosynthetic efficiency [ 14 ]. Besides, intermittent lighting was shown to be capable of enhancing the nutritional value of crops by inducing the accumulation of secondary metabolites [ 9 , 15 , 16 ].…”

Rerouting Artificial Light for Efficient Crops Production: A Review of Lighting Strategy in PFALs

“…Sweet potato plantlets cultivated in intermittent blue and blue-red light tend to have a higher net photosynthetic rate and leaf area compared with intermittent red light, resulting in significantly higher dry matter [47]. On the other hand, intermittent lighting was capable of enhancing the economic value of crops by inducing the accumulation of secondary metabolites, such as anthocyanin in pak choi and tatsoi [51], or soluble polysaccharides biosynthesis in Dendrobium officinale [52].…”

“…Notably, intermittent lighting was an effective strategy for regulating the photosynthetic pathway of CAM plants [54]. A short light/dark cycle of 2 h/2 h was reported to switch the photosynthetic pathway of Dendrobium officinale from CAM to C3, resulting in increased net CO 2 exchange amounts and higher biomass [52]. However, this process is incompletely reversible, as D. offcinale maintained an increased net CO 2 exchange amount when transferred back to 12 h/12 h [54].…”