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IVES 9 IVES Conference Series 9 Shoot heterogeneity effects in a Shiraz/R99 vineyard

Shoot heterogeneity effects in a Shiraz/R99 vineyard

Abstract

[English version below]

Nous avons fait des recherches sur l’effet de l’hétérogénéité des bourgeons sur les paramètres de la croissance végétative et reproductive, la physiologie de la vigne et la composition du raisin dans une parcelle de Shiraz/Richter 99. Des bourgeons sous-développés (typiquement plus courts et moins mûrs à la véraison) ont été comparés avec des bourgeons normaux dans un couvert ombragé ou exposé à la lumière. Comparés aux bourgeons sous-développés, les normaux ont eu une plus grande surface feullière totale à cause du plus grand nombre de entre-cœurs aussi bien que des feuilles plus grandes portées par les bourgeons principaux et entre-cœurs. Vu que l’activité physiologique des feuilles des bourgeons normaux était supérieure à celle des bourgeons sous-développés, une quantité d’hydrates de carbone supérieure a été produite et mise en réserve par les premiers. L’amidon se distribuait plus régulièrement le long des sarments normaux, plus épais et longs en comparaison avec les sarments sous-développés. Les grappes plus grosses des sarments normaux ont montré que la surface feuillère totale par gramme de raisin était plus favorable. Cinq semaines après la véraison les baies des sarments normaux étaient plus petites que celles des sarments sous-développés, montrant un rapport entre peau et pulpe plus grand et un plus grand potentiel d’extraction des anthocyanes et de phénols pour l’élaboration du vin. L’étrange absence d’une grosse différence de composition du raisin entre les deux types de bourgeons a montré que les assimilés nécessaires pour mûrir les raisins des bourgeons sous-développés dérivent d’autres organes que leurs feuilles [p.ex. des bourgeons normaux adjacents et du reste de la structure permanente de la vigne (le cordon, le tronc, les racines)]. Cette hypothèse est supportée par la différence de dimensions de la baie entre les deux types de bourgeons qui était supérieure à l’ombre par rapport au feuillage exposé à la lumière. L’activité photosynthétique était inférieure à l’ombre que dans le feuillage exposé. La production totale d’hydrates de carbone des bourgeons normaux ombragés apparaissait insuffisante aux besoins de maturation de leurs propres grappes et du bourgeon même aussi bien que pour la maturation du sarment et des grappes des bourgeons sous-développés. Cela était démontré par le niveau d’amidon accumulé dans les sarments normaux, qui était inférieur à l’ombre par rapport aux sarments dans le feuillage exposé. Puisque l’hétérogénéité des bourgeons de la vigne a porté à un déséquilibre physiologique qui peut avoir une influence négative sur la qualité du raisin et du vin aussi bien que sur le coût de production, il faut l’éviter sur tout terroir.

The effect of shoot heterogeneity on vegetative and reproductive growth parameters, vine physiology and grape composition was investigated in a Shiraz/Richter 99 vineyard. Comparisons between underdeveloped (typically shorter and less ripened at véraison) and normally developed shoots in both shaded and well-exposed canopies were made. Compared to underdeveloped shoots, normal shoots had a larger total leaf area, due to the higher occurrence of secondary shoots as well as larger leaves on primary and secondary shoots. Since the physiological activity of the leaves from normal shoots was higher than that from underdeveloped shoots, higher levels of total carbohydrates were produced and stored in the former. Starch was more evenly distributed over the whole shoot length in the longer and thicker normally developed shoots compared to the underdeveloped shoots. The larger clusters of the normally developed shoots were evidence of their more favourable total leaf area per gram berry mass. Berries from the normally developed shoots were smaller at five weeks after véraison than those from underdeveloped shoots, displaying a higher skin to pulp ratio and therefore higher anthocyanin and total phenolic extraction potential for winemaking. The peculiar absence of large differences in grape composition between normally and underdeveloped shoots indicated that assimilates needed for berry ripening of the latter originated in organs other than the leaves [e.g. from adjacent normal shoots and the rest of the permanent structure of the vine (cordon, trunk, roots)]. The larger differences in berry size that occurred between shoot types in the shaded compared to the well-exposed canopies may be evidence for this. The photosynthetic activity of shoots was lower in shaded than in exposed canopies. The total carbohydrate production of the normal shoots in shaded canopies seemed insufficient to supply in the ripening needs of their own clusters and of the shoot itself as well as the ripening of stem tissue and clusters of the underdeveloped shoots in the canopy. This was illustrated by the lower levels of starch that accumulated in the normal shoots from shaded compared to that of exposed canopies. Vine shoot heterogeneity clearly led to visible and physiological imbalances that would impact negatively on grape and wine quality as well as production costs and should therefore be avoided on any terroir.

DOI:

Publication date: January 12, 2022

Issue: Terroir 2004

Type: Article

Authors

H Cloete (1), E Archer (2), V Novello (3) & JJ Hunter (4)

(1) Department of Viticulture and Oenology, Private Bag X1, Matieland, University of Stellenbosch, 7602 Stellenbosch, South Africa
(2) Lusan Premium Wines, PO Box 104, 7599 Stellenbosch
(3) Dipartimento di Colture Arboree, I 10095 Grugliasco
(4) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, South Africa

Contact the author

Keywords

Shoot heterogeneity, physiology, vegetative growth, reproductive growth, grape composition

Tags

IVES Conference Series | Terroir 2004

Citation

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