The relation between the date of heading of Nigerian sorghums and the duration of the growing season.
Abstract
Indigenous sorghum varieties in N. Nigeria yielded best in their own localities. All local varieties of a locality tended to flower at the same time each year, and this time was associated with the average date on which the rains ended in that locality. When a variety was grown elsewhere, it still flowered at a time corresponding to the average end of the wet season in its own locality; since the rains ended progressively earlier from S. to N., flowering was then out of phase with the end of the rains and the yield was therefore lower. The adaptation of flowering to the average end of the rains was probably a photoperiodic effect which normally operated several weeks before the end of the rains. It was not a response to critical daylength but could be an effect of the number of successively shorter days which the plants experienced.-R.B.