Effect of Molybdenum and Inorganic Nitrogen on Molybdenum Redistribution in Black Gram ( Vigna mungo L. Hepper) with Particular Reference to Seed Fill

Author： Jongruaysup S. dell B. Bell R.W. O'hara G.W. Bradley J.S.

Publisher： Oxford University Press

ISSN： 0305-7364

Source： Annals of Botany, Vol.79, Iss.1, 1997-01, pp. : 67-74

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Abstract

Seeds used to plant a crop may contain sufficient molybdenum (Mo) to prevent subsequent Mo deficiency in the crop even when they are sown on Mo deficient soils. However, little is known about either the sources of the Mo acquired by the seed, or the timing of its redistribution during seed development. A glasshouse experiment was set up to examine the effect of Mo supply and nitrogen source on the redistribution of Mo within black gram, from full flowering to seed maturity. Treatments comprised two sources of N (symbiotic N 2 fixation, NH 4 NO 3 ), two levels of Mo supply [nil (-Mo), 0.64 mg Mo kg -1 soil (+Mo)] and four harvests (full flowering, early pod setting, late pod filling and seed maturity). The redistribution of Mo in black gram was examined by determining changes over time in the content of Mo in plant parts at each growth stage.Molybdenum supply and the plant growth stage strongly affected the redistribution of Mo to the seed. In -Mo plants reliant on symbiotic N 2 fixation, Mo redistributed from roots, stems and leaves was the only source of Mo for reproductive development since, from full flowering until maturity, there was no net increase in whole plant Mo. For pod and early seed development, the roots were the major source of Mo in -Mo plants. After late pod filling, nodules replaced roots as the major source of Mo for seed fill in -Mo plants. By contrast, for +Mo plants reliant on symbiotic N 2 fixation, Mo taken up from the soil after full flowering could have supplied nearly 50% of the seed Mo. The major sources of Mo for seed filling in +Mo plants were middle stem leaves during early podding, and middle stems and pod walls from late podding.Supplying NH 4 NO 3 to plants from sowing had little effect on Mo distribution or redistribution in +Mo black gram plants. However, in -Mo plants it accelerated the loss of Mo from middle stems and their leaves compared to nodulated plants.