Inflorescence of grapevine (Vitis vinifera L.): a high ability to distribute its own assimilates.

The distribution of carbon (C) into whole grapevine fruiting cuttings was investigated during flower development to determine the relative contribution of inflorescence and leaf photoassimilates in the total C balance and to investigate their partitioning towards other plant organs. A (13)C labelling procedure was used to label C photoassimilates by leaves and inflorescences in grapevine. Investigations were carried out at various stages of flower/berry development, from separated cluster to fruit set, using grapevine fruiting cuttings with four leaves (Vitis vinifera L. cv. Chardonnay). This is the first study reporting that, during its development, (i) the carbon needs of the inflorescence were met by both leaf and inflorescence photosynthesis, and (ii) the inflorescence amazingly participated significantly to the total C balance of grapevine cuttings by redistributing an important part of its own assimilates to other plant organs. With regard to flowering, 29% of C assimilated by the inflorescence remained in the inflorescence, while partitioning towards the stem reached 42% and, as a lower proportion, 15% in leaves, and 14% in roots.