Effect of Shoot Number on Potted Grapevines: II. Dry Matter Accumulation and Partitioning

¹ Department of Horticulture, Michigan State University, East Lansing, MI 48824-1325.

Potted, one-year old Chambourcin grapevines were grown with one, three, or six shoots in the absence of fruit to determine the impact of increasing early-season leaf area on dry weight accumulation throughout the growing season. No fruit was retained so the role of vegetative sinks could be more carefully studied. Very few differences in dry weight were found for various organs (roots, trunks, shoots, and leaves) among the three treatments. Six-shoot vines had greater shoot weight just after bud burst, but at veraison and harvest, there was an inverse, linear relationship between shoot number and shoot dry weight. Three- and six-shoot vines had greater leaf and total canopy dry weights (leaves + shoots) at harvest only. Total plant dry weight was positively related to shoot number at harvest with three- and six-shoot vines having about 20% greater dry weight than one-shoot vines. No differences were detected in vine dry weight at any other time during the growing season. While dry weight differences were not large, increasing shoot numbers affected canopy morphology. Specific leaf and shoot weights decreased as shoot numbers increased, but leaf area per unit shoot weight increased. Additionally, the ratio of cane fresh weight to perennial storage tissues was inversely related to shoot number. This supports the hypothesis that cane fresh weights are of questionable value when used to estimate the cropping capacity of minimally pruned vines.

Key words: carbohydrates, source/sink relations, growth flush

Submitted on April 20, 1995

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