where dc is the diffusivity of H2O in air (2.43x10-5m2 s-1), SD is the stomatal density (m-2), a is the mean stomatal pore area (m2), v is the molar volume of air (0.024 m3 mol-1), l is the depth of the stomatal pore (m, approximated as the width of a single
guard cell) and I is the mathematical constant.
The lengths and widths of stomatal pores and
guard cells were measured using ocular micrometer.
of stomata will reduce then the
guard cell size will increase at same surface.
After microscopically examining 70 different specimens of Agave and Yucca, it is apparent that the stoma and
guard cell patterning of these two desert succulent genera are distinct.
The accumulation and release of potassium by stomata
guard cells lead to changes in their turgid, resulting in stomata opening and closing (Fletcher et al., 2007).
ABA is synthesized following turgor deficiency and stimulates NO synthesis in stomata
guard cells. It was also reported that wilting increases the NO emission from pea plants (Leshem & Haramaty, 1996) but some researchers obtained contradictory results in Arabidopsis thaliana (Magalhaes et al., 2000).
Xylem sap pH increase: A drought signal received at the apoplastic face of the
guard cell that involves the suppression of saturable abscisic acid uptake by the epidermal symplast.
An ESA 5020
guard cell was set to +1.1 V and installed between the pump and the autosampler (I55200; Perkin-Elmer).
Miller-Rushing and colleagues found that stomatal density declined while
guard cell length increased in oaks and hornbeams, although these changes were not dependent on the magnitude of changes in CO2 concentrations.
Each stoma is surrounded by two specialized
guard cells that open and close the central gas exchange pore (fig.