Page Title Grapes, cont. Site and Climatic Considerations 1. The above stages of development vary with the season and cultivar Flower differentiation takes place during the summer for next year's crop, and is complete by leaf fall.
Flower differentiation is triggered by carbohydrate levels in the vine.
If photosynthesis is reduced, the vine may differentiate a lighter crop for next year . A heavy crop in the current year may reduce carbohydrate accumulation in the vine and reduce next year's crop. These are a problem in appearance and marketing. No ovule development occurs beyond the time of bloom due to a defective embryo sac which results in some or all nuclei degenerating. Pollen tube growth stimulates hormone release that prevents flower abscission.