Response of non-structural carbohydrate content of belowground parts in Equisetum arvense according to the irradiance change during a growing season.

Effects of shading on the growth of Equisetum arvense during the growing season were studied in terms of the dynamics of non-structural carbohydrates (starch, sucrose, glucose). Tubers of 0.04 g dry mass were planted in pots. Plants were cultivated under different radiation conditions (100%, 3%, 100%-->3%, and 100%-->3%-->100%). The carbohydrate concentration in belowground parts responded sharply to the irradiance conditions. Under 3% relative photon flux density (PFD), they could not grow beyond the initial mass and decayed. Dry mass per length of rhizomes was highly correlated with the starch concentration, which was correlated with the mass of current tubers. The rhizomes of low starch concentration did not form current tubers. The carbohydrate concentration of rhizomes increased when the plants were transferred from 3% relative PFD to 100% irradiance conditions. After ca. 2 months of improved PFD, they had the same content of non-structural carbohydrates as the 100% PFD plants.