Molybdenum stress-induced changes in growth and yield of chickpea

Chickpea (Cicer arietinum L.) cv. K 75 was grown in refined sand at variable molybdenum (Mo), i.e., 0.00001, 0.0001, 0.001, 0.02, 0.2, and 2 mg L-1 supplied as sodium molybdate. The symptoms of excess (2 mg L-1) Mo appeared earlier (d 35) than its deficiency at 0.00001 mg Mo L-1 (d 42). In addition to growth depression, the deficiency symptoms initiated as deep chlorosis of old leaflets (middle portion), spreading to young growth, chlorosis intensified, changed to bleaching, affected leaves dried and withered. In Mo deficient (<0.02 mg Mo L-1) chickpea the flowers produced were less in number, smaller, many failed to open/mature leading to lower seed yield. Excess Mo (2 mg L-1) not only reduced the growth, but also developed chlorosis (iron deficiency type) of young leaves, intensifying with increase in age. Leaves, flowers, and pods were reduced in number and size. Mo stress (< >0.02 mg Mo L-1) decreased the biomass, seed yield (number and weight) and deteriorated the quality of produce. The concentration of Mo in various parts of chickpea increased with an increase in Mo supply. The seed yield was highest at 0.2 mg Mo L-1 whereas the vegetative growth was maximum at 0.02 mg L-1 indicating a higher Mo requirement for economic yield by chickpea. The values of deficiency, threshold of deficiency and threshold of toxicity of Mo were respectively 0.38, 1.2, and 15 mug g(-1) in leaves of chickpea.