Agroecology for Sustainable Food Security - tnsroindia.org.in

Indian Journal Of Natural Sciences ISSN: 0976 – 0997
Vol1 / Issue 2 / October 2010 © IJONS
Effects of Particulate Matter
Particulate matter such as cement dust, magnesium-lime dust and carbon soot deposited on vegetation can inhibit
the normal respiration and photosynthesis mechanisms within the leaf. Cement dust may cause chlorosis and death
of leaf tissue by the combination of a thick crust and alkaline toxicity produced in wet weather. The dust coating
(Figure 5) also may affect the normal action of pesticides and other agricultural chemicals applied as sprays to
foliage. In addition, accumulation of alkaline dusts in the soil can increase soil pH to levels adverse to plant growth.
Figure 5 Cement-dust coating on apple leaves and fruit. The dust had no injurious effect on the foliage, but
inhibited the action of a pre-harvest crop spray.
Effects of Hydrogen Fluoride
Hydrogen Fluoride behaves somewhat similar to sulphur dioxide except that with a few species of agricultural crop
plants it is effective in causing lesions and interfering with photosynthesis in connections two or three order less than
in the case of sulphur dioxide. With the most species it is up to 10 times as effective as sulphur dioxide. However,
recovery of plants from the fluoride effects is much slower than from sulphur dioxide. This difference in rate of
recovery is probably explained by the fact that sulphate, whereas, fluorides can be removed only by the slower
process of volatization or by some obscure chemical reaction. Forage may be rendered unsafe for animal feeding if
more than 50 ppm of fluorine is absorbed.
Effects of Hydrogen Chloride
Hydrogen Chloride is considerably less toxic to vegetation than sulphur dioxide. It causes first a chlorotic margin in
the leaf, which may become necrotic. At higher concentrations, lesions are produced. The threshold concentration is
about 10 ppm a few hours exposure.
Effects of Chlorine
Sirajuddin et al
Chlorine is more toxic to vegetation than sulphur dioxide by a factor of two or three. Lesions are generally marginal
and interveinal. Damage to vegetation caused by chlorine is rare, and most the reported cases are due to accidents or
excessive use of gas for sterilizing [2].
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