EFFECT OF SHOOT NUMBER ON POTTED GRAPEVINES .2. DRY-MATTER ACCUMULATION AND PARTITIONING

Potted, one-year old Chambourcin grapevines were grown with one, three , or six shoots in the absence of fruit to determine the impact of inc reasing early-season leaf area on dry weight accumulation throughout t he growing season. No fruit was retained so the role of vegetative sin ks could be more carefully studied. Very few differences in dry weight were found for various organs (roots, trunks, shoots, and leaves) amo ng the three treatments. Six-shoot vines had greater shoot weight just after bud burst, but at veraison and harvest, there was an inverse, l inear relationship between shoot number and shoot dry weight. Three- a nd six-shoot vines had greater leaf and total canopy dry weights (leav es + shoots) at harvest only. Total plant dry weight was positively re lated to shoot number at harvest with three- and six-shoot vines havin g about 20% greater dry weight than one-shoot vines. No differences we re detected in vine dry weight at any other time during the growing se ason. While dry weight differences were not large, increasing shoot nu mbers affected canopy morphology. Specific leaf and shoot weights decr eased as shoot numbers increased, but leaf area per unit shoot weight increased. Additionally, the ratio of cane fresh weight to perennial s torage tissues was inversely related to shoot number. This supports th e hypothesis that cane fresh weights are of questionable value when us ed to estimate the cropping capacity of minimally pruned vines.