Stomatal penetration

Aqueous solutions with a surface tension of around 70 mN m do not enter the stomatal pore, but penetration of the pore occurs when the surface tension is lowered by addition of surfactant [243]. The mechanism of penetration is by no means simple. The contact angle between the solution and the surface of the pore is important, but there is a suggestion that the morphology of the pore wall is equally important [244]. However, in the pear Pyrus communis L. cr. Bartlett, stomatal penetration of aqueous solution into leaves was promoted by surfactants according to their surface activity [245]. Dioctyl sodium sulphosuccinate was the most effective surfactant used and Tween 20 least effective. However, only 0.5 to 4.5 % of the stomata were penetrated suggesting that stomatal penetration is, indeed, a relatively unimportant pathway of entry to the leaf. 

Uses Advanced wetter/spreader/penetrant spray adjuvant that will significantly lower surf. tens, compared to other spray adjuvants enhances pesticide/herbicide performance through stomatal penetration safe in agric., industrial, and aquatic applies. 

Stevens PJG, Gaskin RE, Hong SO and Zabkiewicz JA Contributions of stomatal infiltration and cuticular penetration to enhancements of foliar uptake by surfactants. Pesticide... 

Wallihan et al. [246] have produced results with spray solutions on citrus trees which suggest that spray solutions were at least partly entering the leaves by way of the stomata solutions with surface tensions below 30 mN m " have since been shown to be able to penetrate into the sub-stomatal regions of leaves [244], the cuticle in this cavity being generally thinner than the external cuticle and thus more readily penetrated by chemicals. 

The existence of relatively polar routes across the cuticle remains controversial, though there may be localized regions of greater permeability. If this is the case, these may facilitate preferential penetration of properly formulated polar herbicides, especially under high-humidity conditions. The use of certain organosilicone surfactants appears to result in the reduction of surface tension to a level which permits mass flow through the stomatal aperture. 

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