Effects of Surfactants on Propanil Penetration through Adaxial Epidermis of <i>Commelina communis</i>

Abstract

The penetration of propanil through the adaxial epidermis of Commelina communis L. with/without surfactants was examined in a solution/membrane/water system. The penetration was linear with time. A nonionic surfactant enhanced the penetration more than anionic and cationic surfactants at 100 ppm. The promotive effect was greater when a nonionic surfactant was added at 100 ppm than at 1000 ppm. The initial penetration rates were 6. 7-442 pmol/mm2/hr depending on the adaxial epidermis used. The log equation of the penetration (a) after treatment and the initial penetration (ao) were in good correlation: log a= 1.176+0.5282 log a0, r2=0.978.The promotive effect (n= a/ao) was log n=1.176-0.4718 log a0. These results indicate that surfactants enhanced the penetration of propanil through the adaxial epidermis in the solution/membrane/water system and that the enhancement was weak when pore penetration was a main route, and strong when membrane penetration was a predominant route. INTRODUCTIONThe activity of a foliar-applied herbicide depends on the concentration of the active ingredient at a reaction site. The cuticle layer (wax+cutin) of plants seems to be a major barrier to the penetration of foliageapplied chemicals. 1,2) Most of herbicides require surfactants to maximize their efficacy for weed control, and the effects of surfactants on the penetration of chemicals have been studied by using plant cuticle (stomatal and astomatal), 3,4) leaf disks5) and whole plant leaves. 6-9) The epidermal cell layer plays an important role in the penetration of chemicals into the mesophyll tissue as well as the cuticle layer. Silcox & Holloway have pointed out that epidermal stripping offered an attractive alternative for f oliar uptake studies in situ, but only suggested that the layer could be easily and consistently removed from the leaf surface. 10) The difference in permeability between adaxial and abaxial leaf surfaces has been reported by several authors. In dicotyledonous plants, chemicals are absorbed in greater amounts through the abaxial leaf surface than the adaxial leaf surface, and this behavior is apparently attributable to the increased number of stomata and thinner cuticles present on the abaxial surf ace. 11-13) Similar data have been obtained in stomatal and astomatal cuticle penetration studies. 4, 14-16) Commelina communis L. is widely used for stomatal studies, whose adaxial epidermis consists of cuticle and a layer of epidermal cells with stomata and is easily stripped from the leaf surf ace. 17,18) The objectives of this work were to measure the penetration rate of propanil through the adaxial epidermis of Comrnelina in a solution/membrane/water system, to assess the effect of surfactants on penetration and to find a correlation between the initial penetration rate and the promotive effect. MATERIALS AND METHODS 1. A daxial Epidermis PreparationCommelina communis L. plants were collected from a field and kept overnight in a vessel at room temperature in the dark. Detached leaves were washed with tap water...

Effects of Polyoxyethylene Nonyiphenyl Ether and Silicon Surfactants on Penetration of Propanil through Adaxial Epidermis of <i>Commelina communis</i>

“…Surfactant NP(8) showed the highest promotive effect approximately 16 times, followed by NP (10), NP (12) and NP (6), and an addition of NP (14) resulted in the lowest effect. There was a parabolic relationship between the EO molarity and the promotive effect, and this order was also consistent with the results of the pot test using barnyard grass, in which an addition of NP (8) to propanil resulted in the most herbicidal activity, and NP (14) the least. l5) Coefficient a ranking of the surfactants was in order of NP (8), NP (10), NP (12), NP (6) and N P (14).…”

“…There was a parabolic relationship between the EO molarity and the promotive effect, and this order was also consistent with the results of the pot test using barnyard grass, in which an addition of NP (8) to propanil resulted in the most herbicidal activity, and NP (14) the least. l5) Coefficient a ranking of the surfactants was in order of NP (8), NP (10), NP (12), NP (6) and N P (14). This order was consistent with that in the result of analysis by substitution.…”