Cuttings have a similar reproductive physiology to vines, and can be used to study grape physiology and to develop haploid plants.

The Gewurztraminer (GW) and the Pinot noir (PN) cultivars of grapevine differ in their sensitivity to environmental factors that can cause flower abscission, cv. GW being the most sensitive. In order to further define the mechanisms leading to abscission, and owing to the importance of sugars in the achievement of sexual organ ontogenesis, we attempted to correlate the chronology of flower ontogenesis with the variations of carbohydrates in the inflorescence. In the vineyard, under optimal climatic conditions, fruit set of cv. GW and cv. PN was 82% and 65%, respectively. The sugar distribution was different in their inflorescences during the entire duration of flower development. Between stages 15 and 17, flowers of GW and PN reached the crucial meiosis stage. At that time, the inflorescences of cv. GW exhibited higher concentrations of starch and sucrose, whereas those of PN presented higher levels of glucose and fructose. Despite higher starch concentrations in GW inflorescences, starch reserves were present in the ovules and anthers of PN but not in those of GW. These results suggest that the higher content of reserve and transport carbohydrates in the inflorescences of GW favour flower development and fruit set under optimal environmental conditions. Furthermore, since meiosis represents a key step of female development, the different sugar concentrations in the inflorescences of the two cultivars at stages 15 and 17 could be related to the sensitivity to flower abscission under climatic stress. In particular, the presence of starch granules in PN ovules and anthers might explain the higher resistance of this cultivar to flower abscission.

To further characterize carbohydrate physiology in grapevine flowers, we examined inflorescence autotrophy in the 'Gewurztraminer' and 'Pinot noir' cultivars, which differ in sensitivity to flower abscission. In both cultivars, positive net photosynthesis occurred in inflorescences. The rate of photosynthesis gradually decreased throughout flower development and there was no net carbon assimilation at fruit set. The rate of photosynthesis was positively correlated with chlorophyll concentration but not to stomatal conductance. Throughout flower development, the internal CO2 concentration increased in inflorescence tissues, suggesting that assimilates are also formed through refixation of respiratory CO2 by the phosphoenolpyruvate carboxylase (PEPC) pathway. Significant differences between the two cultivars were recorded during meiosis, when photosynthesis was higher in 'Gewurztraminer'. We conclude that the inflorescence of grapevine contributes to its own carbon nutrition by photosynthesizing throughout flower development. Moreover, the differential patterns of photosynthesis in the inflorescences of 'Gewurztraminer' and 'Pinot noir' might account for their differing fertilization rates and sensitivity to flower abscission.

As a part of a global project aimed at comparing the physiology of several grapevine (Vitis vinifera L.) cultivars, we tested plant cultivation in trenches under semi-controlled conditions. Vegetative growth of vines of two cultivars, Pinot Noir and Merlot, from different locations, were followed during a 3-year period. Roots of trench-grown vines grew widely, leading to a root architecture closer to that observed under field conditions than that of potted vines. In addition, the root system could be sampled exhaustively for analyses. Although morphologically different, vines of the two cultivars exhibited similar patterns in dry matter production during the whole period, except at early flowering in year 3. Surprisingly, perennial parts accounted for this difference, though both cultivars were grafted onto the same SO4 rootstock clone. Consistently, vines exhibited root necrosis at any sampling date throughout spring, this process affecting more roots for the Pinot Noir/SO4 combination than for Merlot/SO4.

In : International Coastal Symposium (ICS) : 2013 Proceedings (Plymouth, England )International audienceThe climate component of sea level variation displays significant spatial variability, and it is now possible to reconstruct how sea level varied globally and regionally over the past half century. The fact that sea level rose faster than the global mean since 1950 in the central Pacific stimulated a study of decadal shoreline changes in this region. Here, the study of Yates et al. (2013) was extended to two additional atolls (17 islets): Tetiaroa and Tupai in the Society islands. Both atolls remain stable on the whole from 1955 to 2001/02, however with significant differences in shoreline changes among their islets and within the period. A modeling of waves generated by historical cyclonic events in French Polynesia since 1970 reveals consistency between major shoreline changes and cyclonic and seasonal waves. As in previous studies, this suggests that waves' actions are a dominant cause of shoreline dynamics on relatively undeveloped atolls, even if affected by higher sea level rise rates. In such regions, numerous joint analyses of shoreline changes and their potential causes may help to explain the relation between erosion and sea level rise