in their sensitivity to heat stress during both the vegetative and the reproductive phases (Nigam et al., 1994). Peanut (Arachis hypogaea L.) crops grown in the semi-arid tropics are commonly exposed to damaging hot temperatures of above 40؇C.
Heat-tolerant cultivars have been identified in WestThe objectives of this research were to identify the time(s) during Africa on the basis of their superior partitioning of dry reproductive development when hot days reduce yield, and to examine matter to pods (Greenberg et al., 1992).
relations between flower production and sensitivity to heat stress. AtAlthough the reproductive phase is relatively more start of flower bud initiation (21 d after planting, DAP) plants of sensitive than the vegetative phase to heat stress in many the cvs ICGV 86015 and ICGV 87282 were grown either at 28/22؇C crop species (Hall, 1992), no information is available on (optimum temperature, OT) or at 38/22؇C (high temperature, HT) the effect of the timing of heat stress during reproductive or were reciprocally transferred at 3-d intervals between the OT to HT regimes and vice versa, until 46 DAP. Transferred plants remained development on peanut pod yield. Pod number is the in the new temperature regime for 6 d before being returned to their end product of the number of floral buds that produce original regime. All plants were harvested at 67 DAP. In cv. ICGV flowers, the proportion of those flowers that are fertil-86015, transfers between 6 d before and 15 d after flowering (DAF) ized and produce pegs, and the proportion of those pegs significantly (P Ͻ 0.001) affected total number of pegs (i.e., pegs and which develop into pods. Heat stress at any or all of pods) and reproductive (peg and pod) dry weight, with the greatest these stages may reduce pod yield. For example, in effect occurring at 9 DAF. In cv. ICGV 87282, number of pegs and reproductive dry weights were also significantly reduced by transfers common bean (Phaseolus vulgaris L.) and cowpea at 9 and 12 DAF. Heat stress had no effect on flower production or [Vigna unguiculata L. (Walp.)] plants are particularly the proportion of pegs forming pods, but did significantly reduce the sensitive to high night temperature during macro-and proportion of flowers producing pegs. Data presented suggest that it micro-sporogenesis, 6 to 8 and 6 to 12 d before anthesis, is heat stress during floral bud development that determines peg respectively (Ahmed et al., 1992; Gross and Kigel, 1994), number.and heat stress at these stages of development causes male sterility. Plants are also sensitive to heat stress at Plant Environment Lab., Univ. of Reading, Dep. of Agriculture, Cutand the photoperiod was controlled by a manually operated bush Lane, Shinfield, Reading RG2 9AD, UK.