Changes in starch and glucose levels in the epidermis of Commelina communis in relation to stomatal movements

Starch levels in Commelina communis epidermis, were shown to be higher in the dark than in the light, from plants kept under an imposed photoperiodic regime. These changes were also inversely correlated with diffusive conductance (1/diffusive resistance, 1 /R) of the leaves used. Even after advancing the photoperiod by 7 h the changes in starch levels continued for at least 1 d and were still inversely correlated with 1/R. Corresponding changes in glucose levels were measured in the same tissue and were found to correlate with 1/R at the end of the dark period and mid photoperiod, but not at the beginning of the dark period. These changes are discussed in relation to possible mechanisms of stomatal opening and closing.