Effects of contrasting aerial environments on yield potential in cowpea (Vigna unguiculata (L.) Walp)

K.A. Stewart, R.J. Summerfield, F.R. Minchin, B.J. Ndunguru


Factorial combination of two daylengths (11 h 40 min and 13 h 20 min), warm and cool day (33 and 27C) and warm and cool nights (24 and 19C) were imposed on nodule-dependent cowpea cv. K 2809 plants grown in pots in controlled environment growth cabinets. The treatments had marked effects on seed yield which ranged from a minimum of 420 g to a maximum of 72 g per plant. Differences in yield were due mainly to variations in the number of mature seed per plant which, in turn were governed largely by environmental effects on the number of pods that ripened. The pre mature abscission of peduncle reduced yield potential by about one-third; the loss of open flowers reduced it further to an average of 42 per cent; and the subsequent abscission of immature pods meant that the final realization of yield potential was only from 10.5 to 36.9 per cent of the theoretical potential if reproductive structures had not been lost during development.

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