Agronomie 13 (1993) 499-508
DOI: 10.1051/agro:19930606

Réponse de la vigne ( Vitis vinifera L) aux températures inférieures à 0°C. II. Effets d'un refroidissement contrôlé sur des bourgeons latents avant le débourrement

C. Leddet^a, JC Audran^b, J. Dereuddre^a, E. Ait Barka^b and O. Brun<sup>c

a</sup>  Université P-et-M Curie, laboratoire de Cryobiologie végétale, 12, rue Cuvier, F75005 Paris
^b  UFR sciences, laboratoire de Biologie et Physiologie végétales, BP 347, F51062 Reims
^c  Mumm Perrier-Jouet, Vignobles et Recherches, 11, av de Champagne, F51200 Epernay, France

Résumé - Des bourgeons latents de vigne (Vitis vinifera L cv Chardonnay) soumis à un refroidissement progressif (1°C•min ^-1) entre +5°C et -50°C et étudiés en analyse thermique présentent un profil de cristallisation constitué de 3 exothermes successifs. Le premier se situe vers -12,9°C, le second, plus important, vers -17,0°C et le troisième, plus étendu, vers -21,4°C. À l'échelle histologique, les observations réalisées en microscopie photonique montrent que les cristallisations affectent successivement les tissus de la base du bourgeon (1^er exotherme), ceux du bourgeon primaire (2^e exotherme) et enfin ceux du bourgeon secondaire (3 ^e exotherme).

Abstract - Analysis of the response of grapevine latent buds to controlled freezing. The effects of controlled freezing on latent grapevine buds (Vitis vinifera L Chardonnay) were studied by means of differential scanning micro-calorimetry and histological techniques. Buds were excised from shoots taken from plants in a Champagne vineyard and frozen progressively from + 5°C to -50°C (1 °C/min). Figure 1 presents a simplified scheme of the organization of a latent bud. Each bud includes a primary bud with a secondary and eventually a tertiary bud. Thermograms of an entire bud (fig 2A) generally display 3 exotherms at ≈ -12.9, -17.0°C and -21.4°C. Exothermic peaks obtained during programmed freezing of different parts of the buds differed markedly. Bud scales (fig 2B) showed no exotherm. Two exotherms at -18.2°C and -26°C respectively were obtained when the bud was devoid of its basal part (fig 2C), whereas the 2 peaks of the basal part of the bud occurred at -13.3 and -20°C (fig 2D). When the principal and the secondary buds were frozen separately without their basal parts, they presented only 1 crystallization peak which occurred 3.2 degrees higher in the main bud than in the axillary bud (fig 2E, F). The first exotherm induced histological alterations in the pith of the basal part of the bud (figs 3-5). The second exotherm induced some ruptures of the cell wall (fig 6) and an extension of the cytoplasm contraction to the cells through the basal third of the pith; the other parts of the bud remained apparently intact (fig 7). The third exotherm produced irreversible alterations throughout the main bud (figs 8-11), whereas the meristematic cells seemed to remain intact (fig 12).

Key words: frost / latent bud / thermal analysis / tolerance / Vitis vinifera = grapevine

Mots clés : gel / bourgeon latent / analyse thermique / tolérance / Vitis vinifera = vigne