Effects of duration of bulb chilling on dry matter distribution in hydroponically forced tulips

Bulbs of tulip (Tulipa gesneriana L. 'Gander'), in which the formation of f loral organs had been completed, were chilled at 2 degrees C for 3-30 weeks and then forced hydroponically at 20 degrees C under a 12 h photoperiod wi th the light at 100 mu mol m(-2) s(-1). The fresh weight and the perianth l ength of the cut Bower highly correlated with the dry weights of shoots and floral organs at anthesis, respectively. The dry weights at planting (DWp) of shoots, floral organs and daughter bulbs increased with increasing the duration of bulb chilling at 2 degrees C (t(c)). After a 30-week t(c), enla rgement of daughter bulbs had already started and their DW, was high. The d ays from planting to anthesis (t(pa)) decreased hyperbolically with increas ing t(c). The dry weight at anthesis (DWa) of shoots increased with increas ing t(c) up to 12 weeks and then decreased. DWa of floral organs decreased and that of daughter bulbs increased with increasing t(c). After a 30-week t(c), the DWa values of shoots and floral organs were markedly small and th at of daughter bulbs was very large. The dry weights of shoots, floral orga ns and daughter bulbs increased exponentially after planting, and the relat ive growth rate during the period from planting to anthesis (R-pa) in each plant part was calculated. The changes of DWa of each plant part after vari ous t(c) could be explained by their changes in the growth parameters, i.e. , DWp, t(pa), and R-pa which were shown as functions of t(c). (C) 2000 Else vier Science B.V. All rights reserved.