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

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.

Circadian disturbance induces erectile dysfunction by impairing endothelial function

In order to explore the impact of circadian disturbance on erectile function,we randomly divided 24 adult male rats into groups of control(light on at 8:00 a.m.and off at 8:00 p.m.),dark/dark(DD;constant dark),light/light(LL;constant light),and shift dark/light(DL;light off at 8:00 a.m.and on at 8:0o p.m.).Four weeks later,erectile function was measured and corpora cavernosa were harvested for analysis.The maximum intracavernous pressure(mlcP)and mCP/mean arterial pressure(MAP)ratio in the DD,LL,and DL groups were significantly lower than that in the control group.The LL and DL groups showed significantly attenuated endothelial nitric oxide synthase(eNOS),while DD,LL,and DL showed reduced neuronal nitric oxide synthase(nNOS)at both mRNA and protein levels.The production of nitric oxide(NO)and cyclic guanosinemonophosphate(cGMP)was inhibited by altered light/dark cycles to varying degrees.Circadian disturbance impaired endothelial function and contributed to erectile dysfunction.For the core circadian elements,mRNA expression of circadian locomotor output cycles kaput(Clock)and brain/muscle aryl-hydrocarbon receptor nuclear translocator-like protein 1(Bmal1)was elevated in the DL group,but their protein expression was not significantly changed.DD,LL,and DL increased period 1(Per1)and Per3 levels,while LL and DL increased PER1 levels.No significant difference was found for Per2levels,and PER2 and PER3 concentrations were not significantly changed.Moreover,LL and DL significantly increased cryptochrome-1(CRY1)and CRY2 at both mRNA and protein levels.The altered light/dark rat model showed that circadian disturbance contributed to erectile dysfunction probably by impairing endothelial function.Meanwhile,the core circadian elements were detected in the corpora cavernosa,but these were disrupted.However,which circadian element regulates erectile function and how it works need further analysis.