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IVES 9 IVES Conference Series 9 Canopy photosynthetic activity and water relations of Syrah/R99 as affected by row orientation on a particular terroir

Canopy photosynthetic activity and water relations of Syrah/R99 as affected by row orientation on a particular terroir

Abstract

[English version below]

L’activité photosynthétique et les relations hydriques de plantes de Syrah sur R99 un mois après la véraison ont été étudiées dans un vignoble de la région de Stellenbosch. Le vignoble, planté à 2,75 entre rangs et 1,5 m sur le rang, sur un sol de type Glenrosa, était en pente et exposé a l’ouest: pour les rangs on avait adopté une orientation nord –sud. Les plantes, conduites selon un système de type en cordon de Royat, avaient donc un port ascendant de la végétation, palissée dans un plan vertical à l’aide de trois paires de fils. Une irrigation à micro-jets était appliquée dans la phase comprise entre la nouaison et la fermeture de la grappe et à la véraison. Le tronc était ébourgeonné et la végétation rognée à 1,4 m de hauteur. On a mesuré la photosynthèse et le potentiel hydrique de feuilles en position basale, médiane et apicale soit des bourgeons principaux, soit des entre-cœurs. On a considéré des entre-cœurs en position apicale, médiane et basale le long du bourgeon principal. Soit le matin, soit l’après-midi on a examiné le coté est et le coté ouest du rang.. On a comparé la photosynthèse et le potentiel hydrique de feuilles situées à l’extérieur ou à l’intérieur de la végétation: on a considéré séparément les feuilles apicales, médianes et basales des bourgeons principaux et les feuilles médianes des bourgeons anticipés, situés en position apicale, médiane et basale.
Le nombre de couches du feuillage augmente typiquement du sommet à la base de la végétation et la pénétration de la lumière baisse en proportion. Sur les bourgeons principaux l’activité photosynthétique de toutes les feuilles était plus élevée le matin que l’après midi, soit pour la face au soleil soit pour celle à l’ombre. La photosynthèse des feuilles exposées directement au soleil diminuait du sommet vers la zone basale. Sur le côté à l’ombre la photosynthèse des feuilles médianes était plus limitée en comparaison aux feuilles apicales et basales. L’activité photosynthétique de la plante entière était donc plus importante le matin que pendant l’après-midi. Le potentiel hydrique des feuilles exposées au soleil était beaucoup plus bas que celui des feuilles ombragées. Même si on s’attendait un potentiel hydrique inférieur pour le côté ensoleillé, les différences n’ont pas été en ligne avec les différences importantes trouvées pour l’activité photosynthétique. Le côté ensoleillé du rang avait un potentiel hydrique légèrement plus bas le matin que l’après midi. Les bourgeons secondaires de la zone basale sur le coté exposé au soleil avaient une activité phothosynthétique plus élevée le matin par rapport à l’après midi, tandis que pour les bourgeons secondaires en position apicale et médiane l’activité était à peu prés la même pendant toute la journée. Dans le cas des bourgeons secondaires l’activité photosynthétique des feuilles exposées par rapport aux feuilles ombragées et leur potentiel hydrique suivaient un comportement (matin contre après midi et côté soleil contre côté ombragé) analogues à celui des feuilles des bourgeons principaux.
Si l’on compare l’activité photosynthétique et le potentiel hydrique des feuilles externes et internes du couvert en position différente on trouve le même modèle de comportement pour les deux types de bourgeons que l’on avait observé pour le côté exposé ou non exposé du couvert. Pendant la matinée des grandes différences se produisaient entre les feuilles internes et externes de la végétation sur la face ensoleillée du rang, tandis que, si l’on prend ces mesures du côté ombragé, les valeurs de toutes les feuilles sont pareilles à celles des feuilles internes du côté ensoleillé.
Ces résultats fournissent des indications sur les performances photosynthétiques et sur les relations hydriques que l’on peut s’attendre, en rapport à un terroir particulier, si l’on choisit une orientation donnée des rangs.

The photosynthetic activity and water relations of a Syrah/R99 vineyard, situated in the Stellenbosch region, were investigated approximately one month after véraison. Vines were vertically trained, spur pruned, and spaced 2.75 x 1.5 m in North-South orientated rows on a terroir with Glenrosa soil and a West-facing slope. Microsprinkler-irrigation was applied at pea berry size and at véraison stages. The 1.4 m high canopies were suckered, shoot-positioned and topped and accommodated by means of three sets of double wires. Photosynthetic activity and water potential were measured on leaves in apical, middle and basal positions on both primary and secondary shoots. Lateral shoots in apical, middle and basal positions were measured. Both East and West sides of the canopy were measured in the morning and in the afternoon. In addition, photosynthesis and water potential of interior and exterior leaves on primary (apical, middle and basal leaves) and secondary (middle leaves in apical, middle and basal positions) shoots were compared.
The canopy typically increased in number of leaf layers from top to bottom. Light penetration decreased in tandem. On primary shoots, photosynthetic activity of leaves on sunny and shaded sides of the canopy was higher in the morning than in the afternoon. Photosynthesis of sun-exposed leaves decreased from the apical to basal position. On the shaded part of the canopy, photosynthesis of middle leaves was reduced compared to apical and basal leaves. The photosynthetic activity of the canopy was therefore higher in the morning than in the afternoon. Water potential of leaves on the sunny side of the canopy was also consistently lower than that of leaves on the shaded side. Although the sunny side is expected to display lower water potential, the differences were, however, not in line with the large differences found for photosynthetic activity. The sun-exposed side of the canopy had slightly lower water potential in the morning than in the afternoon.
Basally positioned secondary shoots on the sunny side of the canopy had higher photosynthetic activity in the morning than in the afternoon; that of secondary shoots in apical and middle positions was, however, similar in the morning than in the afternoon. Photosynthetic patterns of leaves on the sunny side of the canopy versus the shaded side of the canopy were similar to those on the primary shoot. Water potential patterns of leaves on secondary shoots (morning versus afternoon and sunny side versus shaded side) were similar to those of leaves on primary shoots.
Comparing the photosynthetic activity and water potential of exterior and interior leaves in different positions on either primary or secondary shoots, similar patterns than those found for sunny and shaded sides of the canopy occurred. In the morning, large differences between the exterior and interior leaves occurred when measured from the sunny side. However, when measured from the shaded side, values were similar to those of interior leaves measured from the sunny side and no marked differences between exterior and interior leaves were found.
The results are useful for application to terroirs forcing different row orientations. It provides an indication of the photosynthetic performance and water relations that can be expected with a particular row orientation.

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DOI:

Publication date: January 12, 2022

Issue: Terroir 2004

Type: Article

Authors

V. Novello (1) and J.J. Hunter (2)

(1) Dipartimento di Colture Arboree, University of Turin, Via Leonardo da Vinci 44, I-10095 Grugliasco (TO), Italy
(2) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, South Africa

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Keywords

Terroir, row orientation, vegetative growth, reproductive growth, water relations, photosynthesis

Tags

IVES Conference Series | Terroir 2004

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