Effect of Light/Dark Cycle on Photosynthetic Pathway Switching and CO2 Absorption in Two Dendrobium Species

Abstract

Many Dendrobium species are both ornamental and medicinal plants in China. Several wild species have been exploited to near extinction, and facility cultivation has become an important way to meet the great market demand. Most Dendrobium species have evolved into crassulacean acid metabolism (CAM) pathways in adapting to harsh epiphytic environment, leading to low daily net CO 2 absorption. Photosynthetic pathways of many facultative CAM plants are regulated by various environmental factors. Light/dark cycle plays an important role in regulating the photosynthetic pathway of several CAM species. The aims of this study were to investigate whether the photosynthetic pathway of Dendrobium species could be regulated between C3 and CAM by changing light/dark cycles and the daily net CO 2 absorption could be enhanced by shortening light/dark cycle. In this study, net CO 2 exchange rates of D. officinale and D. primulinum were monitored continuously during two different light/dark cycles conversion compared to Kalanchoe daigremontiana as an obligate CAM plant. The net CO 2 exchange pattern and stomatal behavior of D. officinale and D. primulinum were switched from CAM to C3-like by changing the light/dark cycle from 12/12 h to 4/4 h. However, this switching was not completely reversible. Compared to the original 12/12 h light/dark cycle, the dark, light, and daily net CO 2 exchange amount of D. officinale were significantly increased after the light/dark cycle was changed from 4/4 h to 12/12 h, but those in D. primulinum was opposite and those in K. daigremontiana was not affected. Daily net CO 2 exchange amount of D. officinale increased by 47% after the light/dark cycle was changed from 12/12 h to 4/4 h, due to the sharp increase of light net CO 2 exchange amount. However, the large decrease of dark net CO 2 exchange amount could not be offset by increased light net CO 2 exchange amount, leading to reduced daily net CO 2 exchange amount of D. primulinum . In conclusion, the 4/4 h light/dark cycle can induce the photosynthetic pathway of D. officinale and D. primulinum to C3-like, and improve the daily CO 2 absorption of D. officinale .

Label-Free Quantitative Proteomics Unravel the Impacts of Salt Stress on Dendrobium huoshanense

“…To combat daytime water loss, some C 3 plants evolved the CAM pathway. Dendrobium is a perennial semi-shade herb, and some varieties are facultative CAM plants ( Cheng et al, 2019 ; Li et al, 2019 ). In nocturnal cells, phosphoenolpyruvate (PEP) works as a CO 2 acceptor, which is catalyzed by PEP carboxylase to generate oxaloacetate.…”

Variability of Volatile Compounds in the Medicinal Plant Dendrobium officinale from Different Regions

“…In this study, the categories and contents of volatile compounds in D. officinale from different regions were different, with the samples from Zhejiang Province (ZB1 and ZB2) containing the most, and those from Fujian Province (FB1 and FB2) the least (Table 1). Cheng [16] found that short light/dark cycle can increase the biomass and polysaccharide yield of D. officinale. Different growth condition and symbiotic bacteria in the roots of D. officinale may also lead to differences in volatile components [17], so the categories and contents of volatile compounds in D. officinale from different regions may be caused by the different temperature, humidity, soil conditions or sunshine duration in the different regions.…”

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

“…Nutrient solution was sprayed to the roots one time per hour and 10 seconds for each time. The formula of nutrient solution for aeroponic cultivation was followed by Cheng et al [12] EC and pH of the nutrient solution were controlled at 0.6-0.7 ms/cm and 6.0-6.5, respectively.…”

“…The higher light net CO 2 exchange amounts during short light/dark cycles might be related to stomatal movement, leaf thickness, and leaf anatomical structure. This was due to the fact that the short light/dark cycles could induce the higher stomatal conductances of D. officinale in light period [12] . Structure features of leaf might affect CO 2 concentration in chloroplast stroma [24] , thus affecting the photosynthetic capacity of D. officinale.…”

“…D. officinale as a facultative CAM plant usually has a photosynthetic pathway of coexistence of C3 and CAM under natural conditions [1,11] . Its photosynthetic pathway can be induced into an obligate C3 pathway in 4 h/4 h short light/dark cycle, and its daily net CO 2 exchange amount increases compared with in 12 h/12 h light/dark cycle [11,12] . However, it deserves further study whether short light/dark cycles can significantly promote the growth and development of D. officinale in a long-term cultivation.…”