The effect of early leaf removal on whole-canopy gas exchange and vine performance of Vitis vinifera L. ‘Sangiovese’

The physiological effects induced at the whole canopy level by early vine defoliation, which has already proven to be very effective in reducing crop via diminished fruit-set while achieving loose clusters and better must quality, was investigated. Fruiting ‘Sangiovese’ vines grown in large pots were subjected to a pre-bloom defoliation (D) by removing the first six basal leaves from each shoot and compared to non-defoliated control (ND). Vegetative growth and grape yield and composition were assessed along with seasonal canopy net CO2 exchange rates (NCER) measured via an enclosure method. While confirming that early defoliation sharply reduced fruit set, cluster compactness and yield per shoot, the post-treament seasonal NCER/vine data were slightly higher in ND vines (13.3 μmol·s-1 vs. 12.2 μmol·s-1 recorded for D canopies). Yet, when these data were given on a per unit of area basis, defoliated vines showed higher rates than ND vines (4.75 μmol·m-2·s-1 vs. 4.16 μmol·m-2·s-1). Overall, NCER/yield (shoot basis) increased by 38 % in D vines, thus resulting in enhanced carbohydrate content for ripening; this finding accords well with advanced maturation and highly improved must soluble solids concentration. The solid physiological background of this early defoliation technique now warrants further investigation in terms of mechanical viability.

Whole-canopy and single-leaf gas-exchange responses to partial rootzone drying in potted 'Cabernet Sauvignon' grapevines

Single-leaf and whole-canopy gas exchange were monitored for two weeks on 6-year-old 'Cabernet Sauvignon' grapevines (~ 6 m2 leaf area) grown with their root system split between two 40 L pots. Beginning July 28, water was withheld from one pot while the second was kept well watered (referred to hereafter as the PRD treatment). The control vines had both pots well watered. The PRD vines were rewatered on 11 August. One half of each vine's canopy was enclosed in a flowthrough, whole-canopy chamber system for continuous monitoring of CO2 and H2O differentials. The other half of the canopy was used for concurrent single-leaf measurements of net CO2 assimilation (A), stomatal conductance (gs), transpiration (E) and midday water potential (Ψ1) taken 3 days before July 28 and 2, 5, 9 and 12 days thereafter and at re-watering. Volumetric soil water content was monitored at the 30 cm depth by Time Domain Reflectometry. Pre-dawn leaf water potential (ΨPD) was measured on day 11 of stress. Soil moisture approached the wilting point in the dry pot 2 days after water was withheld. The ΨPD of the PRD treatment (-0.25 MPa) was not significantly different from that of the control (-0.17 MPa) at day 11. Canopy net CO2 exchange rate (NCER) was reduced by 24.4% in the PRD treatment for the two week period and was similar to the reduction (-27.2%) in a single-leaf basis. Leaf g s and E were reduced for the PRD treatment during the two weeks by 23 and 25%, respectively, as compared to the control. Water use evaluated on a canopy basis for the PRD treatment was reduced by only 15% compared to the control. Leaf water potential was unaffected by treatments. Water use efficiency calculated from both single-leaf and whole-canopy readings over the 2-week period showed no differences between treatments

The effect of early leaf removal on whole-canopy gas exchange and vine performance of Vitis vinifera L. 'Sangiovese'

The physiological effects induced at the whole canopy level by early vine defoliation, which has already proven to be very effective in reducing crop via diminished fruit-set while achieving loose clusters and better must quality, was investigated. Fruiting 'Sangiovese' vines grown in large pots were subjected to a pre-bloom defoliation (D) by removing the first six basal leaves from each shoot and compared to non-defoliated control (ND). Vegetative growth and grape yield and composition were assessed along with seasonal canopy net CO 2 exchange rates (NCER) measured via an enclosure method. While confirming that early defoliation sharply reduced fruit set, cluster compactness and yield per shoot, the post-treament seasonal NCER/ vine data were slightly higher in ND vines (13.3 \u3bcmol\ub7s-1 vs. 12.2 \u3bcmol\ub7s-1 recorded for D canopies). Yet, when these data were given on a per unit of area basis, defoliated vines showed higher rates than ND vines (4.75 \u3bcmol\ub7m-2\ub7s-1 vs. 4.16 \u3bcmol\ub7m-2\ub7s-1). Overall, NCER/ yield (shoot basis) increased by 38 % in D vines, thus resulting in enhanced carbohydrate content for ripening; this finding accords well with advanced maturation and highly improved must soluble solids concentration. The solid physiological background of this early defoliation technique now warrants further investigation in terms of mechanical viability

Calibration and evaluation of a STELLA software-based daily CO2 balance model in Vitis vinifera L

This paper describes and evaluates the reliability of a model for prediction of daily carbon balance and dry matter (DM) accumulation in vertically shoot positioned grapevine (Vitis vinifera L.) canopies based on the user-friendly STELLA simulation software. Validation of the model was produced for potted 'Cabernet Sauvignon' grapevines at both low canopy density [LD (≈10 shoots/m of row)] and high canopy density [HD (≈20 shoots/m of row)] by comparing, on a seasonal basis, the modelled daily CO2 balance with the diurnal net carbon exchange rate (NCER) measured using a whole-canopy enclosure method. Estimated daily total photosynthesis (Pn) was linearly correlated with measured NCER for LD (r2 = 0.87) and HD (r2 = 0.86), thereby indicating that despite its simplicity the model led to a fairly good degree of precision, although it tended to slightly underestimate (5% to 8% less) the measured rates and scattering increased at high values of CO2 fixations. Daily total respiration (R) for LD treatment was 29.0% of total daily Pn, with clusters, leaves and stems accounting for 11.8%, 46.7%, and 41.5%, respectively. Daily total R was 24.2% of total daily Pn in HD treatment and single organs contributed 22.3% (clusters), 41.6% (leaves), and 36.1% (stems). The model estimated that 1604 and 1893 g DM per vine accumulated at harvest for LD and HD treatment, respectively, whereas destructive sampling of leaves, stems and clusters yielded 1475 ± 64 g per vine for LD treatment and 1730 ± 96 g per vine for HD treatment, respectively, corresponding to the 91% and 92% of the DM estimated with STELLA, which in its present version does not take into account root respiration

GRADO DI CORRELAZIONE TRA LUCE TOTALE INTERCETTATA E SCAMBIO NETTO DI CO2 IN CHIOME DI VITE

I risultati presentati in questo studio, condotto su Cabernet Sauvignon, dimostrano come la quantit\ue0 di luce intercettata da una chioma di vite sia ben correlata con la sua capacit\ue0 fotosintetica e possa quindi rappresentare uno strumento valido per confrontare, in modo oggettivo, l\u2019efficienza di diverse forme di allevamento

Performance of Croatina under short-cane mechanical hedging: A successful case of adaptation

The hypothesis that short mechanical hedging can be successfully applied even on cultivars with low fruitfulness of basal buds was tested over four years (2000 to 2003) on Vitis vinifera L. cv. Croatina. Yield per vine increased from 23 to 49% on hedged vines as compared to short-cane hand-pruned vines; up to a 30% increase (equivalent to 3c60 nodes per vine) there was no detriment to grape quality, and labor demand was cut by 55 to 60%. Yield compensation in the hedged vines mostly occurred as reduced budbreak; weak or no compensation effects were seen for cluster weight and bud fruitfulness, respectively. A tendency for impaired quality was seen only at the highest node number per vine ( 3c75), while the linear relationship found between yield and node number per vine suggests that short-cane hand-pruning can also be feasible provided that at least 30 nodes per meter of row are retained. These findings indicate that mechanical pruning can be an excellent tool for converting traditionally long-cane pruned cultivars into short-cane pruned with related advantages in terms of more balanced growth and ripening and adaptability to full mechanization

Effects of early defoliation on shoot photosynthesis, yield components, and grape composition

The effectiveness of early leaf removal on high-yielding cultivars Sangiovese and Trebbiano (Vitis vinifera L.) was investigated as a tool for reducing crop potential and for inducing looser clusters that are less susceptible to rot. Fruit set, cluster weight, berry number per cluster, berry size, and cluster compactness were reduced by all defoliation treatments as compared to non-defoliated shoots. Physiological assessment performed in a one-year study on Sangiovese indicated that prebloom removal of the six basal leaves elicited no difference between treatments in mean seasonal assimilation (A) per shoot (2.91 \u3bcmol s-1 for control against 2.81 \u3bcmol s-1 for the defoliated), a fact due to the offsetting action of more vigorous lateral shoot formation and higher A rates for both main and lateral leaves after veraison in the defoliated shoots. Grape composition was improved by defoliation (higher Brix in both cultivars and higher anthocyanins and phenolics in Sangiovese) as a result of more assimilates being available per unit of cropping and smaller berries characterized by an increased skin-to-pulp ratio. The three-year-study on Trebbiano also showed no carryover effects of defoliation on the following year's bud differentiation and very few year x treatment interactions, suggesting the prevailing effects of leaf removal over variability because of climate. Overall, early defoliation may be an excellent tool for yield control, replacing time-consuming manual cluster thinning. A time-consistent response suggests that this practice may also improve grape composition. Copyright \ua9 2006 by the American Society for Enology and Viticulture. All rights reserved