Effects plant growth

Environmental impact studies on NE have been performed. Although undiluted NE inhibits seed growth, no effect on plant growth was observed when exposed to 6, 000 ppm-min of NE and only minor effects were observed at the 60, 000 ppm-min exposure level (41). Exposure of microbial populations to 25% NE in air for seven hours showed normal growth. NE is not an o2one-depleting gas (20). 

Naphthalene Acetic Acid and Naphthalene Acetamide. Naphthalene acetic acid [26445-01-2] (38) is historicaHy one of the first plant growth regulators. Reports concerning its activity in crops and plants have been a subject in much of the eady Hterature (57). Consequently, it has been used as a starting matedal for other compounds, eg, vide infra Sevin. Naphthaleneacetamide [31093-43-3] (39) has been used as a standard matedal to evaluate abscission pnor to 1953 and its effect on apple drop was reported in 1953 (58). The substance is used as an internal standard in the abscission bioassay (59). 

W. Rademacher, "Biochemical Effects of Plant Growth Retardants," in Plant Biochemical Regulators, Marcel Dekker Inc, New York, 1991. 

CitroneUal can also be converted to the ds- [92471-23-3] (88) and / 3 -/)-menthane-3,8-diol [91739-72-9] (89) by reaction with dilute acids (176,177). The glycol mixture can be readily purified by distillation and the two isomers easily separated. The glycols are usehil as insect repellents (qv) and are especially effective against mosquitos (178). Derivatives of the glycols have been prepared and are usehil as insecticides and plant growth regulators (179). 

The nonvisual or subtle effects of air pollutants involve reduced plant growth and alteration of physiological and biochemical processes, as well as changes in the reproductive cycle. Reduction in crop yield can occur without the presence of visible symptoms. This type of injury is often related to low-level, long-term chronic exposure to air pollution. Studies have shown that field plantings exposed to filtered and unfiltered ambient air have produced different yields when no visible symptoms were present (5). Reduction in total biomass can lead to economic loss for forage crops or hay. 

As far as the effects of contamination are concerned, the main problems associated with harm to plant growth... 

Table 8. Effect of supergd on soil properties and plants growth [10, 131]... 

Biological effects and stimulation of plant growth induced by hydrogel additives are observed at doses which are often much lower than those obtained from purely physical evaluation. For example, it has been recently shown [13] that, according to various criteria of plant development, the SAH additives even at dosages of 50 to 140 kg ha-1 provide a productivity in sandy soils at the level obtainable by treatment with 20% (of the order of hundreds of tons per 1 ha) alluvial deposits. There seems to exist a mechanism allowing the plants to efficiently utilize small water reserves contained in the SAH particles. 

The early literature on naturally occurring plant growth inhibitors and the influence one plant might exert on another by chemical means (allelopathy) is considered comprehensively in various reviews (12, 15, 36, 37, 48, 49, 61, 67, 94, 121, 162). Reviews of studies concerned with the influence of plant exudates on root-infecting fungi (130) and the effects of phytotoxins which arise as decomposition products (113) have appeared recently. Because of the excellent coverage of the topics by others, no attempt is made here to review the early literature exhaustively. Instead, consideration is restricted essentially to specific compounds and to some of the more recent literature. 

Volatile Inhibitors. Of the volatile components that influence plant growth and development, ethylene has received the most attention. Literature concerned with the variety of effects produced by ethylene, factors which influence its production, and the mechanisms through which responses are expressed has been reviewed by Evenari (57). Other gaseous excretions with inhibitory effects considered by Evenari include hydrogen cyanide, ammonia, essential oils, and mustard oils (probably allyl isothiocyanate and /3-phenethyI isothiocyanate). 

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