Micropropagated Lilium speciosum Thunb. bulblets were cold-treated at 2C for various periods before being planted in soil. About 20% of uoncold-treated bulblets and 100% of bulblets cold-treated for 6 weeks sprouted within 10 weeks after planting. Intermediate lengths of cold treatment resulted in intermediate percentages of emergence. The remaining 80% of the noncold-treated bulblets sprouted synchronously from 25 to 33 weeks after planting. In these bulblets, the number of scales increased before sprouting. A sample of bulblets that had received a short cold treatment (2 or 3 weeks) also showed biphasic emergence, with the second period between 25 and 33 weeks. When the cold treatment was interrupted by 3 weeks at 17C, the percentage of emergence during the first period was reduced and the timing of the second period advanced.
Ornamental geophytes comprise a large and diverse group of plants characterized by underground storage organs that serve the obvious function of reserve storage and subsequent supply during early stages of shoot growth. Relative to many agronomic and horticultural crops, the fundamental physiological bases of carbon metabolism, partitioning, and utilization in geophytes are unclear. One reason is diversity in organ morphology (bulb, corm, tuber, root, rhizome, etc.), storage carbohydrate (starch, fructan, glucomannan, etc.), and growth habit (e.g., synanthous vs. hysteranthous flowering). Knowledge of factors that control accumulation and mobilization of carbohydrate reserves may lead to manipulations that considerably improve the quality and culture of these crops. We are utilizing a variety of techniques and experimental systems to study selected internal and external controls or influences on geophyte carbohydrate metabolism and partitioning. Specific examples to be discussed include bulb storage temperature effects on starch and fructan metabolism in Tulipa, effects of carbon source and dormancy breaking treatments on starch and glucomannan metabolism in in vitro-grown Lilium bulblets, photoperiod control of fructan accumulation in Dahlia seedlings, and biochemical and molecular features of soluble and wall-bound invertases in developing Lilium longiflorum flower buds.