Effects of complete leaf shading during the late reproductive period on carbon and nitrogen distribution and seed production by nodule-dependent cowpea (Vigna unguiculata) plants

Maria C.P. Neves, Rodney J. Summerfield, Frank R. Minchin


Nodule-dependent plants of cowpea cv. 'TVu 1503' were grown to harvest ripeness in a plastic house and were allowed either to mature normally or were subjected to complete foliar shading by covering all leaves individually with aluminium foil for the final 31 days of the life cycle. Leaf shading markedly reduced total plant dry weight because it decreased the dry weights of both vegetative and reproductive components. In the unshaded controls, current photosynthesis and assimilation of symbiotically-fixed N during the later stages of the reproductive period, when most fruits were filling, were the main sources of C and N to the developing seeds. Although greater proportions of previously-assimilated C and N were mobilized from shaded leaves to reproductive structures than from leaves left exposed, the respective amounts were still insufficient to meet the requirements of developing fruits. The implications of these data in terms of C metabolism and N nutrition of the nodulated grain legume are discussed.


Vigna unguiculata; Carbon; Nitrogen; Seeds

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