ACTIVATION OF SUCROSE-METABOLIZING ENZYMES AND STIMULATION OF SUCROSEUPTAKE BY AUXIN AND SUCROSE IN EGGPLANT (SOLANUM-MELONGENA L.)

Tissue segments prepared from ovaries and fruits of eggplant (Solanum melongena L.) were incubated in the presence of auxin and sucrose, and activities of sucrose-metabolizing enzymes were determined. Activitie s of cell-wall-bound and soluble acid invertases increased in response to exogenous indole-3-acetic acid (IAA) and 4-chlorophenoxyacetic aci d (4-CPA), whereas activities of sucrose synthase (SS) and sucrose pho sphate synthase (SPS) were not influenced by auxin. On the other hand, SS activity increased in response to added sucrose, whereas the activ ities of acid invertase and SPS were not influenced by sucrose. The ef fects of IAA on uptake of sugars into ovary tissues were also examined . The uptake of sucrose, glucose, and fructose by carrier-mediated tra nsport was stimulated clearly by IAA. These results indicate that IAA stimulates both the activation of acid invertase and the uptake of sug ars, and an increased concentration of sucrose stimulates activation o f SS. The sink activity increased in these ways may thus trigger fruit growth.