ACCUMULATION AND DISTRIBUTION OF ~(14)C-PHOTOSYNTHATE DURING BULB DEVELOPEMNT OF Lilium ORIENTAL HYBRID Distribution of 14C-photosynthate and Changes of Endogenous Phytohormonein the Bulb Development of Tulip ( Tulipa gesneriana L. ) Distribution of 14C-photosynthate and Changes of Endogenous Phytohormonein the Bulb Development of Tulip ( Tulipa gesneriana L. )