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This study was carried out in order to investigate the damage mechanism caused by excessive boron (B) in Cicer arietinum L. Excessive B higher than 1 μM caused visible injuries such as chlorosis and necrosis. It also induced B accumulation and unbalance of die uptake of inorganic elements. Photosynthetic rate and growth rate also were decreased by 70% and 80%, respectively. Decreased growth rate appeared more severe in roots than shoots. Aminolevulinic acid (ALA) which is an initial precursor of chlorophyll was almost doubled. Futhermore, ascorbate peroxidase (APx) and glutathione reductase (GR), the two major antioxidative enzymes in plants, showed increased activities by 77% and 40%, respectively, suggesting that reactive oxygen species damaged the plants. Conclusively the excessive B caused physiological disorder in chlorophyll metabolism and induced secondary toxic substances, which led to chlorosis, necrosis, and suppression of growth in Cicer arietinum L.
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