Change in levels of starch and sugars in epidermis of Commelina benghalensis during fusicoccin stimulated stomatal opening

Abstract

The concentrations of malate, starch and sugars were determined in presonicated epidermal strips of Commelina benghalensis. During opening, the starch content of epidermis decreased while the level of sugars or malate increased. Fusicoccin (FC) stimulated stomatal opening and elevated the levels of malate and sugars. However, the contribution from sugars was nearly 50% of the osmotic effect of malate and it increased to more than 60% in the presence of FC. We conclude that FC stimulates stomatal opening by enhancing not only potassium influx into guard cells but also hydrolysis of starch into sugars (and malate). Significant correlations were noticed between the width of stomatal aperture and epidermal starch (negative), malate and sugars (both positive). The negative relationship between starch and malate or sugars within epidermis indicated that starch hydrolysis lead to formation of sugars as well as malate. Starch-sugar interconversion can therefore play a significant role in modulating the solute potential of guard cells. © 1983 Oxford University Press.