COMPETITION BETWEEN SPROUT AND DAUGHTER BULBS FOR CARBOHYDRATES IN TULIP AS AFFECTED BY MOTHER BULB SIZE AND CYTOKININS

Abstract

Planting of large mother bulbs resulted in large tulip flowers, planting of small mother bulbs in small tulip flowers. However, a heavier bulb gave a relatively lighter tulip flower, indicating different mechanisms for the redistribution of fresh weight and dry weight. The possibilities to grow good quality tulips from small sized bulbs were investigated in terms of source sink relationships, for a “splitting” cultivar, cv. Apeldoorn, as well as for a “non-splitting” cultivar, cv. Parade. Over the period between planting and flowering, the recovery percentage of dry matter in generative bulbs depended on the size of the mother bulb, changing from about 70 to 60% for bulb size 14 to 8 respectively. The distribution of dry matter at the moment of flowering also depended on the size of the mother bulb. In small sized (8) bulbs about 85% of dry matter was transported to the tulip flower, in big sized bulbs this percentage was about 40%, resulting in different amounts of dry matter left in the scales. The percentage dry matter transported to the daughter bulbs never exceeded 12% at the moment of flowering. Tulip flowers grown from big sized bulbs also contained a higher percentage dry weight than tulips grown from a small sized mother bulb. Removing scales from a big sized tulip bulb before cold treatment or immediately before planting, resulted in a system comparable to small sized mother bulbs: slightly more dry matter was lost in the period from planting to flowering, a higher percentage of dry matter was transported to the tulip flower, and the tulip flower itself contained a lower percentage of dry weight. Injection of tulip bulbs with benzyladenine (BA) immediately before planting resulted in a higher FW of the tulip flowers. As the DW of the tulips did not increase, this result is due to a higher water uptake. Therefore, the redistribution of DW from source to sink was unaffected by application of BA.