Early Leaf Removal to Improve Vineyard Efficiency: Gas Exchange, Source-to-Sink Balance, and Reserve Storage Responses

Abstract

Based on earlier findings showing the effectiveness of a pre-flowering leaf removal at reducing yield in several Vitis vinifera L. genotypes, a three-year study was carried out on Sangiovese vines to evaluate how the technique also affect vegetative growth, wood carbohydrates reserves and specific physiological traits such as intrinsic water use efficiency (WUEi) and leaf chlorophyll fluorescence. Early defoliation (D) applied before flowering with elimination of about 80% of the leaf area as compared to a non-defoliated control (C) confirmed to be quite effective in limiting yield per vine, cluster weight, cluster compactness and rot incidence, berry set and mass in two out of the three season. Defoliation also markedly improved relative berry skin mass regardless of season. Vine vigor (pruning weight, cane diameter and main leaf area) was significantly reduced in D vines (2008–2009 data), whereas vine capacity as total leaf area per vine was not. Upon the dramatic drop of the leaf-to-fruit ratio after defoliation down to 1 m 2 /kg in D vines, these recovered hereafter and showed a higher ratio from veraison onward. Intrinsic WUE and tolerance to photoinhibition increased in D vines for both main and lateral leaves which were formed after leaf stripping and which had reached full maturity by the time measurements were made. Berry sugaring were accelerated in D vines also showing, at harvest, higher must Brix and phenolic and anthocyanin concentrations as compared to C vines as well as more stable anthocyanins in the wine.