EFFECT OF GIBBERELLIC ACID ON SUGAR TRANSPORT INTO PETALS OF "MADELON" ROSE FLOWERS DURING BUD OPENING
Individual petals from several stages of flower bud opening were placed on well plates containing different solutions. Weight and surface area were measured after a seven days experimental period on the wells. The petals were divided into three groups according to their requirements to obtain a size comparable to their size in the final stage of intact flowers. The number of petals which only need water to expand increased during flower bud opening. At the same time the number of petals, which depend on water + carbohydrates + gibberellic acid (GA3)decreased when flower opening progressed. During flower opening the petals first lost their dependence on GA3, then temporarily required water + carbohydrates, and eventually lost their need for carbohydrates.
GA3 served as an activator of the active component of the uptake of carbohydrates by petals. The passive (diffusion) component of carbohydrate uptake was weak in these petals.