Foliar concentration

Owing to ion exchange, bipyridyls are immediately inactivated on contact with most soils. Thus, ten times the practical foliar concentration can be applied on the soil without damaging plants growing in it. 

Though several studies on mineral elements in tropical forests (Golley et al., 1975 Ashton, 1982 Pampasit et al., 1998) have been conducted, there are very few studies (Jayasekera, 1993) concerning heavy metals. This paper describes the foliar concentrations of 11 heavy metals in 20 tree species from a mixed dipterocarp forest in Sarawak, Malaysia. The concentrations given can be considered natural as this ecosystem is largely undisturbed by anthropogenic activities. 

Lawler IR, Foley WJ, Eschler BM (2000) Foliar concentration of a single toxin creates habitat patchiness for a marsupial folivore. Ecology 81 1327-1338... 

A 25-g sample of <150- o.m control soil was placed into each of six jars for fortification. Three samples were fortified at each of two concentrations of oxamyl. Soil samples were fortified on the same days and at the same levels as the foliar... 

The theoretical initial concentration on leaves is 10 ug/cm2, based on an application rate of 1 kg/ha, no loss of spray to the ground or into the air, and a leaf area index (LAI) of only 1, which means that the total foliar surface in a treated area is equal to the ground surface. 

Vascular plants including trees. Effects are related to HM toxicity, such as the reduced growth of roots and shoots, elevated concentrations of starch and total sugar and decreased nutrient contents in foliar tissues and depressed biochemical activity ... 

Plant Species Ozone Concentration, ppm Exposure Time, h Plant Growth Response, % reduction from control Foliar Injury Response, % increase over control Reference... 

Ozone and sulfur dioxide mixtures are of special interest, because of their widespread occurrence and the greater than additive effect on Bel W, tobacco. Concentrations of either or both that may cause foliar injury are found around major metropolitan areas throughout the world and are widespread throughout rural eastern United States. Macdowall and Cole reported that the two-gas combination lowered the threshold for injury of tobacco (cultivar White Gold) by sulfur dioxide, but not the threshold for ozone injury. Macdowall et defined the threshold in terms of dose when th reported the threshold at 20 pphm-h (0.20 ppm-h). This has not appeared true in several other reports, nor within the results reported by Macdowall and Cole. Symptoms reported, when sulfur dioxide was below the threshold for the specific plant, were similar to those reported for ozone. 

Plant Species Concentration Ratio. SOitO). ppm Exposure Duration, h Foliar Injury, % Response to Mixture Reference... 

TABLE 11-21 Effects of Time and Concentration on Foliar Response of Selected Plants to PAN... 

The bioassay technique was developed to reduce the uncertainties associated with the use of native vegetation or cultivated crops. Plants can be started under controlled conditions and exposed under standardized conditions. Species and cultivars can be selected for oxidant sensitivity and symptom characteristics. The two studies just noted were the most closely controlled. Similar work has not been repeated. However, many investigators have grown plants under known cultural conditions and then transplanted them to field sites where they received special care. These plants can then be read for foliar symptoms throughout a given period, and the symptoms related to oxidant concentrations. The lack of apparent correlation in the two early studies could be due to the lack of specificity for the monitored oxidants, the presence of different concentrations of interacting oxidants at different times, or variations in cultural conditions between exposure times. 

Jacobson, J. S.. and W. A. Feder. A Regional Network for Environmental Monitoring Atmospheric Oxidant Concentrations and Foliar Injury to Tobacco Indicator Plants in the Eastern United States. Massachusetts Agricultural Experiment Statioo Bulletin No. 604. Amherst University of Massachusetts, College of Food and Natural Resources, 1974. 31 pp. 

Plant Although no products were identified, the half-life of chlorpyrifos in Bermuda grasses was 2.9 d (Leuck et al., 1975). The concentration and the formulation of application of chlorpyrifos will determine the rate of evaporation from leaf surfaces. Reported foliar half-lives on tomato, orange, and cotton leaves were 15-139, 1.4-96, and 5.5-57 h, respectively (Veierov et al., 1988). 

Veierov, D., Fenigstein, A., Melamed-Madjar, V., and Klein, M. Effects of concentration and application method on decay and residual activity of foliar chlorpyrifos, J. Econ. Entomol., 81(2) 621-627, 1988. 

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