Penetration, foliar

Baker, E.A., Hayes, A.L., Butler, R.C. (1992) Physicochemical properties of agrochemicals their effects on foliar penetration. Pestic. Sci. 34, 167-182. 

Schonherr, J. and Riederer, M., Foliar penetration and accumulation of organic chemicals in plant cuticles, Rev. Environ. Contam. Toxicol., 108, 1-70, 1989. 

Schonherr J, Baur P and Buchholz A Modelling foliar penetration its role in optimising pesticide delivery, Pesticide Chemistry and Bioscience (The Food - Environment Challenge), Brooks GT and Roberts TR (Eds), Royal Society of Chemistry, Cambridge... 

Although non-ionic surfactants do not always maximally promote foliar penetration, their presence in formulations is often preferred because of their greater spectrum of compatibilities especially when concentrates are diluted with water of low quality, hard water and water of high salt content. 

The foliar penetration of water-soluble herbicides is relatively inefficient in comparison with that of lipophilic compounds, no doubt reflecting the incompatibility of the polar droplets and the nonpolar epicuticular waxes, and also the relative inefficiency of transcuticular polar transport. The choice of a suitable surfactant certainly reduces the degree of incompatibility and may also enhance passage through the membrane. 

Inhibitors must possess chemical and physical properties that will ensure absorption by root tips or penetration by foliar surfaces, and translocation to the active site. Once there they must assume the precise spatial configuration required to complement the molecular architecture of the active center if they are to block the key reaction. A comprehension of comparative biochemistry and information on how plants differ in the architecture of the reactive sites should assist in developing truly selective herbicides. 

DeLucia EH, Day TA, Vogelmann TC (1992) Ultraviolet-B and visible light penetration into needles of two species of subalpine conifers during foliar development. Plant Cell Environ 15 921-929... 

Other important members of the azolyl-0,N-acetal family that have been marketed thus far are bitertanol (Baycor, Sibutol) and the imidazole derivative climbazole (Baypival). Bitertanol is not systemic, but penetrates plant tissue and thus possesses curative and eradicative properties combined with protective activity. It is used for control of foliar diseases of various crops such as tree fruit, peanuts and bananas. 

The foliar absorption coefficient k ranges from 0.3 to 1.3 for most plants. Light penetrates the vertically oriented blades of grasses rather easily in such cases, k can be near 0.4. What cumulative leaf area per ground area reduces the incident PPF by 95% for grasses with such a foliar absorption coefficient By Equation 9.5, the accumulated leaf area per unit ground area in this case is... 

Figure 9-7. Variation in leaf angle and hence foliar absorption coefficient with distance above the ground for (a) various idealized plants and (b) sugar beet measured at various canopy positions (Hodariova, 1979). Hie greater erectness of the uppermost leaves leads to a lower k for them and hence to better penetration of PPF down to the lower leaves.

Another new method of spray application which may improve foliar deposition is called air-assist spraying (10). This application system involves spraying air along with the pesticide to enhance penetration of crop canopies. With more spray impacting the plant, not only is environmental impact reduced but the performance of insecticides, fungicides, foliar fertilizers, and growth regulators is vastly improved. 

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

The low partition coefficient of 1 indicates that it has no potential to accumulate in biological tissues and, therefore, also not in the food chain. The rapid uptake and translaminar transport of 1 is excellent, as observed in cabbage leaves [23] and in rice and cucumber [24]. Additionally, 1 has a considerable acropetal mobility in xylem of plants. In contrast, its penetration and translocation in cotton leaves was less pronounced, as shown by phosphor-imager autoradiography [25]. This xylem mobility makes 1 especially useful for seed treatment and soil application, but it is equally active for foliar application. Owing to its lack of any acidic hydrogen, the pK of 1 is >14 and, therefore, its transport within the... 

Several combination products of 9 have been developed for foliar treatment, e.g., the suspo-emulsion marketed as Monarca (SE 112.5, 9+beta-cyfluthrin) and Proteus (9+deltamethrin). The latter is based on the new O-TEQ formulation, which increased the penetration of the active ingredients remarkably. 

The fungus attacks the plant through the root system, where it penetrates 1-2 mm from the root tip and grows toward the vascular system (3). Hyphae in the xylem vessels produce spores that are transported upward in the xylem fluids and eventually infect the foliar plant parts (4). To prevent this systemic infection, the plant must seal the infected vessels and kill the fungus. 

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