Abstract
The influence of sucrose as an important factor in the vase-life of cut flowers has been dually noted. Sucrose is actively transported across the cell membrane via a symport system and the membrane-imbedded ATPase enzyme generates the required energy and proton gradient for the process. The activity of this enzyme decreases during the senescence of Petunia petals, concomitant with a decrease in sucrose-uptake in the post-climacteric phase. However, ATP does not appear to be limiting, indicating that a change in proton gradients may be responsible for this phenomenon. In order to study the uptake of sucrose in Petunia corollas various inhibitors of ATPase enzyme activity (DES and sodium orthovanadate) were introduced. The effect of potassium ferricyanide on the disruption of the membranal electro-chemical gradient was also determined. In addition it was found that the plasma membrane redox system seems to be influential in creating the H+-gradient necessary for sucrose-uptake. These effects were also studied in relation to prior treatment of flowers with the hormone, ethylene, for 24 hours. The results obtained have shown the i) importance of a stable inter- and intracellular pH environment; ii) the imbedded ATPase enzyme’s dependence on the membrane stability; iii) the maintenance of the electro-chemical gradient across membranes; the active energy generated by the ATPase enzyme; and lastly, iv) the effect of ethylene directly on membrane integrity and indirectly on sucrose-uptake.
Prof. C.S. Whitehead