Agriculture Reference
In-Depth Information
Chapter 13
Arsenic Stress in Plants: An Inside Story
Iti Sharma
Abstract
Arsenic (As) toxicity is a global concern due to increasing contamina-
tion of metalloid in water, soil and crops especially in South East Asia. Arsenic
poses a serious threat of food chain contamination by accumulating in various crops
through the phosphate transporters as a phosphate analogue. After accumulating
in plant tissues arsenic interferes with various metabolic processes and thereby
adversely affects the plant metabolism, and ultimately leads to reduced plant pro-
ductivity. Alteration of phosphate, nitrogen, sulfur metabolism and disorder in
major physiological reactions like respiration, photosynthesis and transpiration are
responsible for metabolic dysfunction of plants exposed to arsenic. This chapter
discusses recent advances in plant arsenic interaction at molecular, biochemical and
physiological levels. It is necessary to develop a detailed biochemical understand-
ing about interaction of arsenic with plants to limit detrimental effects of arsenic on
crops and also for better agronomic production.
Introduction
Arsenic (As) is an environmental and food chain contaminant. The toxicity of arse-
nic was known as early as in 300 B.C. It has been used at least from the 12th century
A.D in metallic form. It bears a sinister connotation linked to suicides, witchcraft
and murder and it was a source of despair and inspiration to alchemists wishing
to transform metals into gold (Azcue and Nriagu
1994
). Arsenic is a metalloid of
group VA in the periodic system. It is a natural constituent of the lithosphere and oc-
curs in some 200 minerals, frequently as mixed sulphides. Metal oars such as lead,
gold, zinc and copper, volcanic eruptions and sea spray liberate arsenic naturally,
and it can be methylated, demethylated and volatilized by soil bacteria (Matscullat
2000
). Anthropogenic sources of arsenic pollution are spreading of herbicides or
pesticides, coal combustion and timber preservatives. High-temperature urban
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