RE-MOBILIZATION AND REDISTRIBUTION OF RESERVES IN THE TULIP BULB IN RELATION TO NEW GROWTH UNTIL ANTHESIS.

The organic carbon content and the amount and identity of [SUP14]C-labelled compounds derived from the [SUP14]C-leaf assimilates fixed in the previous season were examined in various organs of tulip bulbs at replanting, on transfer to the glasshouse and at anthesis. Differences in the partition of reserves to various organs were related to the timing of their development and growth, their sink strengths and to their position relative to source organs (initially the bulb scales, later also the leaves). Leaves and roots were the major sinks which received 75% of the [SUP14]C-reserves exported from the scales in the first three months at low temperature (the first period). After 21 days at 18°C up to anthesis (the second period), the new leaves were a further source of carbon for the continued growth of the flower, stem and daughter bulbs. Daughter bulbs appeared to be the only organs still receiving carbon from the scales during the second period, and this was stored mainly as starch. A high rate of respiratory loss of carbon by the whole tulip plant, and particularly by the scales, was indicated in the second period. [ABSTRACT FROM AUTHOR]