Endogenous Diurnal Rhythm in the Osmotic Surplus of the Guard Cells

The osmotic surplus of the guard cells — i.e ., the difference between the guard cells’and epidermal cells’omotic value at incipient plasmolysis ( Vicia Faba ) —exhibits an endogenous diurnal‐periodic variation that is synchronous with the endogenous diurnal periodicity in the movements of the guard cells. The osmotic surplus of the guard cells is found to arise and drop by changes not only in these cells, but also in the epidermal cells.