Changes in minimal diffusive resistances of leaf epidermes during ageing of primary leaves of phaseolus vulgaris L.

Minimal diffusive resistances of both leaf epidermes increased during normal and retarded ageing (moving secondary leaves aside, plant decapitation). The retarded ageing of primary leaves slowed down increase in epidermal resistance (r_ep), and was also reflected in the prolongation of their growth, increase of leaf area, size of epidermal and guard cells and stomatal pores. Decrease of stomata density was to some extent balanced by an increase in the pore size; the later rapid rise in diffusion resistance was induced by the loss of stomata ability to open fully.