EXCESS SULFUR PARTIALLY ALLEVIATES COPPER DEFICIENCY EFFECTS IN MUSTARD

Mustard (Brassica campestris L. var. sarson) cv. T42 was grown in refined sand at two copper levels, deficient (10(-8) M) and normal (10(-6) M), each at two molybdenum levels, normal (5 x 10(-7) M) and excess (10(-4) M), and two levels of sulphur, normal (2 x 10(-3) M) and excess (4 x 10(-3) M) with nitrate and ammonium nitrate as nitrogen sources. In mustard, excess sulphur interacted with copper deficiency when the supply of excess sulphur at adequate molybdenum levels partially alleviated the effects of copper deficiency namely, visible copper deficiency symptoms, decrease of dry weight, seed yield and the activity of cytochrome oxidase. The alleviation of copper deficiency effects by excess sulphur was also discernible at excess molybdenum levels. Excess S interacted with excess Mo in decreasing significantly the tissue Mo contents for both nitrogen sources. Excess S also significantly depressed the NR activity in the NO3 treatment at both levels of Mo supply, indicating the presence of an interaction between excess S and N source. Several other interactions were also revealed.