The Effects of Temperature and Daylength on the Rate of Development of Pigeonpea

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Abstract
Eleven cultivars of pigeonpea, representing five different maturity groups, were grown under controlled conditions to determine how the rate of development from sowing to flower bud initiation (FBI) and sowing to flowering was affected by temperature and daylength, the two environmental variables thought to have most influence on reproductive development. Both temperature and daylength had substantial effects over the range 16–32 °C and 10–14 h respectively. Comparisons within the 12 h daylength treatment showed no consistent pattern with mean temperature. A discrete-rate analysis was used to determine the effect on development of each of the temperatures making up the various treatment combinations of day and night temperature. The rate of development from sowing to FBI varied among cultivars. The responses to temperature were all strongly curvilinear with optima between 20 and 24 °C. The rate of development from sowing to flowering showed a similar pattern. The effect of daylength on the rate of development was the greatest between sowing and FBI, with the greatest sensitivity between 12 and 14 h. For the range of conditions considered, temperature had at least as great an influence as daylength on the rates of development from sowing to FBI and from sowing to flowering. Some of the responses to time of planting that have previously been attributed to daylength effects may, in fact, have been due to temperature. The responses to temperature of reproductive and vegetative development are very different.