| Abstract: | In tomato seedlings the effects of high temperature in delayingthe enlargement of the shoot apex and of increasing the numberof leaves produced before flowering, were counteracted by removalof the first two leaves during the early vegetative phase. Inplants grown at 25° C. defoliation was followed by rapidenlargement of the apex and earlier flower initiation, the numberof leaves produced before flowering being reduced to that inplants grown at 15° C. Defoliation of plants grown at 15°C. resulted in only a slight increase in the rate of apicalenlargement, and the time to flowering and number of leaveswere unaffected. Growth analysis showed that at the time ofremoval, the first two leaves were not self-supporting and at25° C. were utilizing a much higher proportion of assimilatetranslocated from the cotyledons than at 15° C. These resultsare considered to support the view that at higher temperatures,the first two leaves compete strongly with the shoot apex forsupplies of assimilate. |
