2000 Volume 69 Issue 3 Pages 353-361
Bulbs of Tulipa gesneriana L. 'Gander' were 1) stored at 20°C dry for 4-26 weeks and then chilled at 2°C for 8 weeks, or 2) stored at 20°C for 8 weeks and then chilled at -2°, 2°, 5° or 9°C for 6-36 weeks. The bulbs were forced and grown hydroponically at 20°C under 12-hr photoperiod. Relative growth rate from planting to anthesis was calculated for newly developing organs (shoots, floral organs, and daughter bulbs). The duration of storage at 20°C affected only the dry weights of new organs at planting much, and scarcely affected the number of days from planting to anthesis and the relative growth rates. The bulbs chilled for 6 weeks at -2° or 2°C flowered earlier and had higher relative growth rates of new organs than the bulbs chilled at 5° or 9°C. However, when the duration of chilling at 5° or 9°C was extended, the growth of new organs more advanced at planting and the flowering was earlier. Longer chilling resulted in 1) a decrease in dry weights of shoots and floral organs at anthesis in the bulbs chilled at -2° and 2°C, 2) failure to flower in the bulbs chilled at 5° and 9°C, and 3) an increase in dry weight at anthesis of daughter bulbs which is competitive with shoots at any temperatures. The enlargement of daughter bulbs at planting in the bulbs chilled at 2°, 5° and 9°C or their increased relative growth rate in the bulbs chilled at -2°C resulted in an increase in dry weight of daughter bulbs at anthesis. In these experiments, most of growth indexes i.e. number of days from planting to anthesis, dry weights of new organs at planting and anthesis, and relative growth rates of new organs, correlated nonlinearly with the duration of bulb storage at 20°C and chilling at different temperatures.
