Effects of Succinamic Acid 2,2-Dimethylhydrazide Treatment on Cell Size, Acid Invertase and Sucrose Phosphate Synthase Activities, and Sugar Content of Melon Fruit

To determine the relationship between cell size, acid invertase (AI) and sucrose phosphate synthase (SPS) activities, and sucrose accumulation in melon (Cucumis melo L.), fruit were treated with succinamic acid 2,2-dimethylhydrazide (SADH) at various developmental stages during spring and summer. Fruit and cell growth was suppressed by SADH treatment during early, but not middle, development. Higher AI activity and lower SPS activity and sucrose content were observed in fruit with smaller cells exposed to early SADH treatment, compared to fruit with larger cells exposed to late SADH treatment. These results suggest that the low sucrose content in fruit treated with SADH during early fruit development is due to the lower SPS activity of smaller cells resulting from SADH exposure.