194 



THE FLOWERING PROCESS 



The Requirement for Active Buds (32, 38) 



There has been much speculation about what happens within the 

 plant when it is converted to the induced state. A cocklebur plant 

 seems to be incapable of completing the act of induction unless active 

 bud tissue is present. If all of the buds are removed from a plant, 

 which is then given a series of long dark periods, the plant is incapable 

 of causing a vegetative receptor to become reproductive when it is 

 grafted to it. Even if the active buds are removed just prior to 

 induction, and dormant buds are left on the plant, they will usually 

 be vegetative when they finally become active (Fig. 10-5). In order 

 to be reproductive they must become active within 5 or 6 days after 



100 



± 80 - • 



60 - 



40 



UJ 



o 20 

 a: 



UJ 



Q. 4- 



Control 



Active buds not removed 



\ 



Cotyledonary bud \ i 



left on plants \ 



\ 

 . \ 



C 



\ 



\ • Axillary bud left on plants 



O ^ 



\ 



\ 



54321 I 234567 



DAYS BEFORE OR AFTER INDUCTION (time of active bud removal) 



Figure 10-5 



Effects on per cent flowering of removing active buds at various times 

 before or after an inductive dark period. One curve was obtained by 

 using plants with all buds removed at the times shown but the cotyle- 

 donary ones, which were then allowed to become active so that they could 

 be checked for flowering. The other curve shows results obtained by 

 removing all buds but a single relatively dormant axillary one. Note 

 that removal of buds which are already flowering (beginning about 3 days 

 after induction — Fig. 5-9) still causes the dormant ones to be vegetative 

 when they become active. Data from F. B. Salisbury, 1955, Plant 

 Physiol. 30, 327-334. 



