Agronomie 13 (1993) 491-498
DOI: 10.1051/agro:19930605

Réponse de la vigne (Vitis vinifera L) aux températures inférieures à 0°C. I. Effets d'un refroidissement contrôlé sur des sarments aoûtés

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

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

Résumé - Afin de simuler les effets d'un froid hivernal, des fragments de sarments aoûtés de vigne ont été soumis artificiellement à un refroidissement programmé de 1°C.mm^-1, entre +5° et -50°C. Les thermogrammes obtenus en microcalorimétrie différentielle à balayage présentent 2 exothermes successifs : le premier, nettement marqué vers -9°C, le second, plus étalé, débute vers -17°C et persiste jusqu'à -30°C. Corrélativement à ces pics de cristallisation les analyses histo-cytologiques ont montré des seuils thermiques de dégradation sélective des différents tissus caulinaires : parenchyme cortical et vaisseaux conducteurs du bois (-10°C), liber (-17°C) et cellules médullaires (-30°C).

Abstract - Analysis of the response of grapevine mature shoots to controlled freezing. The effects of controlled freezing on mature shoots of grapevine (Vitis vinifera L cv Chardonnay) were studied by differential scanning microcalorimetry and histological techniques. One-yr-old shoots were taken from plants in a Champagne vineyard and frozen progressively from +5°C to -50°C (1°C/min). Figure 1 presents thermograms obtained from different parts of the shoot. Thermograms generally displayed 2 exotherms at ≈ -10°C and -17°C respectively, whatever the nature of the explant: a piece of shoot, bark or pith. However, secondary xylem thermograms presented only 1 crystallization peak. Histological alterations due to the formation of ice appeared after the first exotherm and involved the bark (figs 2, 3) and the secondary xylem vessels (figs 9, 10 and 11), whereas other tissues (the cambium and liber) remained unaltered (fig 6). After the second exotherm (between -17 and -30°C) every tissue was affected: the bark (fig 4), the liber and cambium (figs 5, 7 and 8), and the secondary xylem (fig 12). In conclusion, although some destruction inside the shoot seemed to have been induced by freezing at -9°C, it only concerned the superficial tissues and did not affect further development of the plant. Further freezing < -17°C appeared necessary to destroy liber and secondary xylem vessels.

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

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