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  • Author or Editor: K.A. Fisher x
  • Journal of the American Society for Horticultural Science x
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Abstract

Cluster-thinning of the French hybrid grape cultivar ‘de Chaunac’ (Vitis sp.) resulted in superior fruit quality and an increase in vigor of the vines in comparison to the unthinned vines in a similar pruning and management regime. The higher sugar levels associated with thinning are consistently desirable for wine making under Ontario conditions. The favorable test site used limited the expression of vine decline and winter injury usually associated with over-cropping of this cultivar in the Niagara Peninsula of Ontario.

Open Access

Potted `Chardonnay' grapevines (Vitis vinifera L.) with either two or three shoots were grown in a greenhouse for one month and then transferred to a phytotron room, where either one or two shoots were shaded. Twenty-four days after transfer, leaves at the fifth node of either the light-adapted or shade-adapted shoot were exposed to a 2-hour pulse of 14CO2. Both light environment and number of shade shoots on the vine had a significant effect on photosynthate partitioning within the plant following a 22-hour chase. Leaves fed with 14CO2 on a light-adapted shoot translocated 26.1% and 12.7% more radioactivity to the roots and trunk, respectively, than leaves from shade-adapted shoots. Photosynthates were exported from light-adapted leaves to shade-adapted shoots (1.3% of total 14C in plant). The number of shaded shoots and the light environment of the fed leaf had a large effect on partitioning of photosynthates among ethanol-insoluble, water-soluble, and chloroform-soluble fractions within the leaf. Recovered 14C in the water-soluble fraction of the fed leaf appeared to be affected more by number of shoots than by light environment of the fed leaf. The data suggest that there is a sink effect on initial carbon partitioning patterns in grapevine leaves. Sink strength may have a greater role than light environment. A large proportion of interior leaves versus exterior leaves may be costly with respect to the carbohydrate budget of a vine.

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