Abstract
Aluminium toxicity in acid soils having pH below 5.5, affects the production of staple food crops, vegetables and cash crops worldwide. About 50% of the world’s potentially arable lands are acidic. It is trivalent cationic form i.e. Al3+ that limits the plant’s growth. Absorbed Aluminium inhibits root elongation and adversely affects plant growth. Recently researches have been conducted to understand the mechanism of Aluminium toxicity and resistance which is important for stable food production in future. Aluminium resistance depends on the ability of the plant to tolerate Aluminium in symplast or to exclude it to soil. Physiological and molecular basis of Aluminium toxicity and resistance mechanism are important to understand for developing genetically engineered plants for Al toxicity resistance. This paper provides an overview of the state of art in this field.
Highlights
It is estimated that around 30% of the world’s total land area consists of acid soils, and about 50% of the world’s arable lands are acidic [1,2]
Malate exudation mechanism by wheat has been investigated most thoroughly [9] while citrate seems to be the most common organic acid anion exudated by Altolerant maize and snapbean [11]
Al toxicity is an important growth limiting factor for plants in acid soils which is comprised in a large area of fertile land, in pH-5 or below
Summary
It is estimated that around 30% of the world’s total land area consists of acid soils, and about 50% of the world’s arable lands are acidic [1,2]. Up to 60% of the acid soils in the world occur in developing countries like in South America, Central Africa and Southeast Asia due to which, food production is critical. Al toxicity in acid soils affects the production of staple food crops, grain crops, by decreasing their yield and vigor. Many of the soils used for agriculture, those in developing countries where forests have been cleared, are considered sufficiently acidic that they restrict the growth of many susceptible plant species. Crop plants have evolved resistance mechanisms that enable them to tolerate toxic levels of Aluminium in acid soils [7,9,10,11,12,13]. An early study in snap bean (Phaseolus vulgaris) [17], followed by a more extensive characterization of the same phenomena in wheat (Triticumaestivum) [18,19], showed that Al-tolerant genotypes exhibit a strong, Al-activated exudation of Al-chelating organic acids (citrate in snap bean and malate in wheat), which is absent or much smaller in the Al-sensitive genotypes
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