Adventitious bud production on explants of Begonia × hiemalis depends on the developmental state of the donor plant

In vitro responses can be influenced by the developmental status of the donor plant tissue. The effects of the donor plant photoperiod and the developmental stage of the plant on organogenesis of petiole explants of Begonia × hiemalis cv. Schwabenland Pink are reported. Long day plants had progressively more branches, total stem length, leaf area, and branch and shoot mass. In short days, flowering was earlier and a greater proportion of dry weight accumulation was allocated to reproductive structures. Similar explant responses were obtained from all developmental stages until flowering was well advanced in short days and then the regenerative capacity diminished. Primary measurements of donor leaves (length, area and weight) at the time of explant removal were not well correlated with adventitious bud production. Loss of regeneration was not determined by tissue or plant age but was associated with the progressive development of flowers. Thus the donor plant photoperiod only indirectly affected bud production. Organogenesis decreased with duration of short days but increased in long days and thus both the duration of the multiplication phase and the intensity of the in vitro response was enhanced by maintaining donor plants in long days.