Paramagnetic behaviour of the differentiating reproductive apex of wheat.

Abstract

A study of the physiological significance of EPR signal was undertaken in the developing apical organs as well as in the top most leaf of a determinate type of plant,Triticum aestivum Cv. S 227 at various stages of vegetative and reproductive differentiation. Pour types of signals are reported: (a) a weak asymmetrical signal having 700 Gauss of width and g=2, the origin of which, is not clear; (b) a broad six peak signal also having g=2 which, as available evidence suggests, may be due to Mn++; (c) in association with Mn++ signal there are also other signals caused either by paramagnetic metals or by organic free radicals (FR); (d) at the centre of Mn++ signal there appears a free radical signal with g=2.0023. It is observed that the amplitude of Mn++ and free radical signal increases sharply in the shoot apex during its transformation from vegetative to reproductive state. The leaf also consistently records higher Mn++ and FR contents at all stages of reproductive differentiation. Synchronously with the above mentioned enhanced paramagnetic behaviour of the apex and of the leaf there is an upsurge in metabolic activity of the plant. The possible role of free radicals and Mn++ in energy transfer is discussed in relation to ascorbic acid turnover.