EFFECTS OF GROWING ENVIRONMENTS, PLANTING DATE, AND STEM TREATMENTS ON SANDERSONIA TUBER WEIGHT AND SECONDARY TUBER DEVELOPMENT

Sandersonia (Sandersonia aurantiaca Hook) tuber growth and secondary t uber development were assessed in two growing environments (a greenhou se and outdoors), at three planting dates (1 October, 1 December, and 1 February) and with six stem pruning treatments. Tubers of c. 1 g wer e used. The pruning treatments consisted of cutting the stem just abov e the second flower when 50% of the stems had the second flower open, or 2, 4, 6, and 8 weeks later. In another experiment the effect of ste m tipping, stem pruning, flower removal, and an auxin transport inhibi tor (2,3,5-triiodobenzoic acid (TIBA)) applied 3 weeks after the secon d flower opened were assessed. Tuber growth and secondary tuber develo pment were affected by the date of planting, with both tuber weight an d incidence of secondary tubers declining significantly in the later p lanting dates. Environmental factors including temperature, radiation, and day length may have influenced the rate and type of tuber growth. Stem pruning, removal of the growing tip plus flowers, or applying TI BA reduced secondary tuber numbers and had little effect on tuber size . This study suggests that it is possible to reduce the presence of un desirable secondary tubers by manipulating the growing environment or by developing appropriate cultural practices.