Calcium signalling mediated the regulation of growth and polysaccharide accumulation by light quality in Dendrobium officinale protocorms

This study selected Dendrobium officinale protocorms as the experimental material and used different light-quality treatments and calcium signalling inhibitors to explore the mechanism of the biological response of calcium to light quality. The results indicate that a 1:3 red:blue (R:B) light ratio promotes the accumulation of biomass and polysaccharides in the protocorm. Nevertheless, this effect can be entirely counteracted by calmodulin (CaM) inhibitors and calcium ion-chelating agents. The possible mechanisms of this effect are as follows: (1) The Ca2+-CaM signal-regulated photosynthetic apparatus is improved by the R:B 1:3 light, increasing the CaM content and Ca2+-ATPase activity. Thus, R:B 1:3 light increases the development of the photosynthetic apparatus in the D. officinale protocorm, enhances its photosynthetic productivity, and promotes the activities of sucrose phosphatase; accordingly, biomass and sucrose accumulation increase. (2) R:B 1:3 light enhances Ca2+-CaM signalling and regulates glycometabolic processes to promote the activities of sucrose synthase, thus increasing fructose and glucose levels and providing sufficient synthetic precursors to promote polysaccharide production.