Relation entre les variations du contenu en acides gras des bourgeons latents et des entre-nreuds de Ia vigne (Vitis vinifera L. var. Merlot) et leur teneurs en eau et en acide abscissique
Creators: name: Koussa, T.
name: Cherrad, Monique
Publisher: name: VITIS - Journal of Grapevine Research
Year: 2015

description: Au cours du cycle annuel, Ia teneur en acide arachidique (C20:0) des entre-nreuds de vigne est faible et stable. Dans les bourgeons latents, Je C20:0, identifie ici pour Ia prerniere fois dans ces organes, est present en forte quantite pendant Ia phase de dorrnance et en teneur plus faible pendant Je reste du cycle. Les teneurs des autres acides gras des bourgeons sont generalerneut superieures a celles des entrenreuds avec des variations sirnilaires. Chaque dirninution de Ia teneur en eau dans Ies bourgeons au cours du cycle annuel s' accornpagne d'une augrnentation de Ia proportion du C20:0. Cet allongernent de Ia chaine aliphatique est concornitant de l'accurnulation de I'acide abscissique (ABA), phenornene qui a pu etre reproduit par deshydratation des bourgeons a 25 °C. La dirninution de Ia teneur en eau s'accornpagne egalerneut de l'augrnentation de Ia proportion de I'acide oleique et de celle de l'acide Iinolenique. Cette derniere cornrnence a dirninuer des que Ia deshydratation devient excessive. Au contraire, lorsque Ia teneur en eau augrnente au cours du cycle annuel ou Iorsque les bourgeons sont traites a 2 °C, Ia teneur en ABA dirninue s'accornpagnant d'une accurnulation des acides palrnitique et linoleique. Tous ces phenornenes, tres nets dans Je cas des bourgeons, Je sont beaucoup rnoins dans Je cas des entre-nreuds. Le röle de I' ABA dans les rnodifications de Ia cornposition des acides gras des bourgeons et des entrenreuds et son influence sur les echanges hydriques avec Je rnilieu exterieur sont discutes. Levels and composition of fatty acids in buds and internodes of Vitis vinifera L. cv. Merlot and their relationship with ABA and water content During the annual cycle, the level of arachidic acid (C20:0) in internodes of Vitis vinifera cv. Merlot was low and stable, while in buds the level of C20:0 was increased during the period of dormancy compared to the growth period. To our knowledge, this is the first report identifying C20:0 in buds of grapevines. In most cases, levels of other fatty acids were increased in buds compared to internodes, with a development similar to C20:0. Each decrease of water content in buds during the annual cycle was accompanied by an increase of the C20:0 proportion and the endogenous abscisic acid (ABA) level. These results have been reproduced on buds exposed to conditions favouring dehydration (25 degrees C). The decrease of water content was also accompanied by an increase of the proportions of oleic and linolenic acids (C18:3), If dehydration was intensive and accompanied by an irreversible loss of the bud burst ability, the C18:3 proportion decreased. If however the water content of buds increased during the annual cycle or if buds were stored at 2 degrees C, the ABA content decreased and was accompanied by an increase of the proportions of palmitic and linoleic acids. All these phenomenons were observed in internodes, but were less clear than in the buds. The effect of ABA on the composition of fatty acids in buds and internodes is discussed in relation to water exchange between grape and ambient air.
description: VITIS - Journal of Grapevine Research, Vol. 39 No. 3 (2000): Vitis