The influence of prolonged dark periods on the concentration of pinitol in white clover (Trifolium repensL. ev. Regal Ladino) and soybean [Glycine max(L.) Merr.] tissue was investigated. Clover and soybean plants were harvested periodically throughout continuous dark periods of 40 and 44 h, respectively, followed by 24 h of continuous light. The foliage and root tissue of clover and foliage tissue of soybeans were analyzed for the concentration of glucose, fructose, sucrose and pinitol. Pinitol concentration (mg/g dry weight tissue) was unchanged by the prolonged dark period followed by 24 h of continuous light compared to tissue of plants harvested at 0‐h and plants receiving normal photoperiods. Concentrations of the carbohydrates, in the tissue were depleted by the prolonged dark period. However after 6 h of light, the concentration of these sugars increased to concentrations equal to 0‐h harvested plant tissue and tissue of plants receiving normal photoperiods. These results indicate that pinitol probably does not function as a source of reserve energy comparable to sucrose, glucose, and fruct