Interactive effect of boron and zinc on growth and metabolism of mustard

Mustard (Brassica campestris L.) cv. T9 was grown in refined sand at three levels of boron (B), deficient (0.0033 ppm), normal (0.33 ppm), and excess (3.3 ppm), each at three levels of zinc (Zn), low (0.00065 ppm) adequate (0.065 ppm), and high (6.5 ppm). The B deficiency effects were accentuated by low zinc viz., the decreased biomass, B and Zn concentrations in leaves and seeds and the activity of carbonic anhydrase and accumulation of reducing sugars and stimulated activities of peroxidase, ribonuclease, and acid phosphatase in B deficient leaves were aggravated further. Synergism was also observed between the two nutrients when both B and Zn were in excess together as excess B accelerated the effects of high Zn by lowering further the reduced biomass, economic yield, and carbonic anhydrase activity and raised further the increased concentration of B and Zn in leaves and seeds, reducing sugars and activity of peroxidase obtained in excess Zn. In mustard, additive effects of high Zn and low B was reflected when high Zn increased the reduced biomass, seed yield, leaf B, and decreased the stimulated activities of peroxidase, ribonuclease, acid phosphatase, and high concentration of non‐reducing sugars to some extent in low B.