T. Eichert, J. Burkhardt, H.E. Goldbach
In this study the influence of air humidity, light, concentration and position on the leaf blade on the uptake of the anionic fluorescent dye uranine (sodium fluoresceinate) was investigated, using isolated epidermal strips (ES) of Allium porrum and of the ornamental plant Sedum telephium. The dye was applied in aqueous solution as single droplets at a defined relative humidity (rh). The proportion that penetrated the ES was immobilised on the inner side by ion exchange membranes (IEM). Uptake patterns were examined microscopically and uptake rates were quantified fluorimetrically. The distribution of the dye on the IEM indicated that uptake was restricted to stomatal areas. Uptake of the dye increased with increasing rh and was particularly high when rh was above the deliquescence point of uranine. Pre-illumination of S. telephium leaf sections increased uptake rates by a factor of 1.5 to 36 compared with leaves kept in darkness prior to the experiments. Increasing the concentration of uranine at a constant droplet volume increased overall penetration rates but decreased uptake relative to the applied dose. This decrease was most distinctive at high rh (93%). This is attributed to the extremely slow evaporation of the droplets at high solute concentrations and high rh. With both plant species variability was considerably high, even if ES were obtained from proximate regions of the same leaf. It is concluded that stomata can be an important pathway for the uptake of foliar applied substances.
Eichert, T., Burkhardt, J. and Goldbach, H.E. (2002). SOME FACTORS CONTROLLING STOMATAL UPTAKE. Acta Hortic. 594, 85-90
DOI: 10.17660/ActaHortic.2002.594.6
Allium porrum, Sedum telephium, concentration, cuticle, deliquescence point, epicuticular wax, humidity, light, stomatal aperture

Acta Horticulturae