ABSTRACT
Soybean is cultivated in a remarkably diverse range of climates, and the timing of developmental events, particularly the initiation of floral primordia and their subsequent expansion into open flowers, differs markedly throughout this wide range of environments, depending on the genotype grown and the date on which it is planted. Rates of phenological development most often have been thought of as being dictated by relative responsiveness to prevailing photoperiod. An ability to explain, quantify and predict photo-thermal effects on flowering, and to screen large populations of diverse genotypes reliably in the field, might be expected to ensure a more rapid development of soybean genotypes well adapted to the regions and seasons for which they are intended. The prediction of phenological development of photoperiodically-sensitive types, based on climatic variables prevailing in the field, still presents difficulties, although some models based on field experiments have been attempted.
