Abstract
Grapevine defoliation is common with many reports of its effect on post budburst reproductive parameters. (i.e.inflorescences) but little is known about the underlying mechanisms of these defoliation effects. We propose low carbohydrate reserves from defoliation reduce numbers of inflorescence primordia (IP) initiated and limit size during development, in the latent bud. From early in Season 1 (December in the Southern Hemisphere) Chardonnay grapevines were totally defoliated progressively, as new leaves appeared, throughout Season 1 until leaf fall, with the fruit remaining intact. The defoliation treatment resulted in low carbohydrate reserves in the dormant wood at season end and consequently smaller IP by dormancy and at pre-budburst in Season 2. Treatment and control grapevines had similar numbers of IP at winter dormancy and by pre-budburst in Season 2. However, post-budburst treatment inflorescences likely underwent necrosis, resulting in inflorescence abortion, with fewer clusters in Season 2. Low reserves during spring of Season 2 gave reduced IP initiation and delay in development with fewer, smaller inflorescences at post-budburst in Season 3. Thus defoliation effects were due to low carbohydrate reserves reducing IP initiation numbers and IP size in latent buds, and also causing abortion of mature inflorescences in the immediate post-budburst period.
- ©2016 by the American Society for Enology and Viticulture
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