Photosynthetic light response curves in relation to illumination of adaxial and abaxial surfaces of sun and shade leaves of Vitis vinifera L.

The photosynthetic light response of adaxial (upper) and abaxial (lower) surfaces of sun- and shade-adapted leaves of cv. Grechetto/SO 4 was investigated. Vines were exposed to long-term shade by mounting a black polypropylene cover (40 % light transmittance) over the vines for 6 consecutive years. The mean leaf blade inclination varied from 81.4degrees(sun-exposed) to 15.4degrees (shaded) enabling a high light reception. At light saturation, the maximum rate of photosynthesis of sun and shade leaves were similar if the adaxial or the abaxial leaf surface or both sides were irradiated simultaneously. At lower photon flux density (PFD), the adaxial surface consistently fixed more CO2 than the abaxial surface in both leaf types. At PFD below saturation, simultaneous illumination of both leaf surfaces led to an increase of the rate of net photosynthesis (Pn) as compared to illumination of only one surface with the same PFD. Bilateral illumination increased the apparent quantum yield and the convexity coefficient (bending rate of the photosynthetic light response curve) as compared to irradiation of only one side of the blade, whereas the light compensation and saturation points were significantly lower. The possible significance of simultaneous irradiation of both leaf surfaces at low PFD on Pn is discussed

Plant and leaf responses to cycles of water stress and re-watering of 'Sangiovese' grapevine

Abstract The complex relationship between water and grapevine has been examined in several studies. The aim of this study was to understand the impact of water stress on photosynthesis, carbon-13 discrimination in leaves in different positions on the shoot, and the capacity of vines to recover from different levels of water stress intensity. The vine physiological responses to a water stress regimen followed by re-watering for two consecutive cycles was evaluated using potted 'Sangiovese' grapevines. The intensity and the duration of the water limitation affected the emergence and development of new leaves, but did not significantly affect leaf water potential. Leaf stomatal conductance and carbon assimilation during the first water-stress phase were reduced respectively by about 61% and 20%, while after the second water stress cycle both were lower than the initial values by 77% and 21%, respectively. After 1 day of re-watering, only the leaves located in the medial positions on the shoot showed a partial recovery of photosynthesis. After at least 2 days post-re-watering, the leaves located in the distal portion of the shoot showed a recovery of photosynthetic capacity. The results indicated that leaf position along the shoot, i.e., an indicator of leaf age, is an important variable in developing grapevine strategies in response to conditions of limited water availability

Ascophyllum nodosum extract improves leaf thermoregulation by reducing stomatal sensitivity to VPD in Vitis vinifera L

AbstractClimate change scenarios and the need of sustainable tools to reduce global warming impact on agriculture have led to the formulation of a large number of natural products or biostimulants that should increase plant resilience to abiotic stress. Ascophyllum nodosum (AN) extract is one of the most studied biostimulants to increase tolerance to drought stress, but the physiological mechanism underlying its action is still poorly understood. The aim of the present work was to determine AN extract impact on grapevine gas exchange under well-watered and water stress conditions and to examine its mode of action under stress (light and temperature). AN caused a slight increase in stomatal conductance that resulted in an increase of water plant conductivity to atmosphere. Increased transpiration induced by AN improved leaf thermoregulation, facilitating vine recovery after a stress period. AN increased transpiration through a reduction of stomatal sensitivity to VPD. AN action on stomata regulation indicated that this biostimulant could be a new potential tool to limit leaf damage during events of extreme temperature, even when they are not combined with water stress conditions

Traditional and innovative summer pruning techniques for vineyard management

This review paper highlights physiological and vine performance effects of widely adopted summer pruning operations such as leaf removal, shoot trimming and positioning and cluster thinning. Leaf removal is addressed either under its traditional configuration, i.e. removing in dense canopies some or all leaves around clusters usually pre-veraison to improve fruit microclimate and facilitate spraying and early (pre-flowering) defoliation primarily aimed at inducing looser clusters via a concurrent reduction of fruit-set and berry size. Time consuming and still non mechanisable cluster thinning is evaluated primarily in terms of response variability vs. season and intensity with emphasis on lack of significant reduction of final yield per vine in thinned treatments when large crop compensation occurs. Variability of expected final grape composition improvements in thinned vines is also discussed based on the actual vine balance when the operation is performed. Although fully mechanisable, shoot trimming is still a debated choice in terms of timing and severity. While severe (i.e. fewer than six or seven main leaves retained) and late (i.e. several weeks after bloom) cuts should possibly be avoided, the effects of shoot trimming on final grape composition is discussed as a function of seasonal changes in leaf area development, demography, fraction of lateral leaves from the total and leaf to fruit ratio. It is indicated that, for vertically shoot-positioned trellises, if the support trellising is correctly designed and vine vigour is balanced, timing and severity of trimming are dictated by the vine “itself” rather than by grower choices. Overall, this review underscores the importance of leading the vineyard to a “natural” control of vegetative growth, which would minimise the need for an extensive use of summer pruning. In other words, such vineyard operations should be viewed not just as something the growers “have to do”, instead as specific tools used to achieve targeted final grape composition

Changes in Within-Shoot Carbon Partitioning in Pinot Noir Grapevines Subjected to Early Basal Leaf Removal

Early leaf removal significantly alters the source-sink balance within grapevine shoots, leading to a reduction in fruit set. However, no research has previously examined the conditions controlling this process in terms of carbon allocation among major sink organs following defoliation. In this study, the impact of defoliation at bloom on the distribution dynamics of leaf assimilates among clusters and growing shoot apices was investigated on Vitis vinifera, cv. Pinot noir, grown in Michigan, a cool climate viticultural region. Three levels of defoliation: no leaves removed (LR-0); six leaves removed from six basal nodes (LR-6); and ten leaves removed from ten basal nodes (LR-10), were imposed at full bloom. A 13C pulsing was performed 1 week after the treatment application to the defoliated shoots. Single leaf gas exchange (Pn), diurnal changes of the leaf net CO2 assimilation rate, carbon distribution, fruit-set, yield, and fruit composition were measured. Higher Pn was recorded in diurnal measurements of gas exchange in leaf removal (LR) treatments compared to LR-0. The shoot apex of LR-10 experienced the highest 13C allocation (%) after 3 and 7 days following the carbon pulsing. LR-10 had lower percentage of 13C allocated to clusters, which decreased fruit set by 60%, compared to the control, and enhanced the concentration of phenolic compounds in fruit. Alteration of carbon portioning among shoot sink organs indicated that an increasing severity of leaf removal significantly reduced fruit set, and was linearly correlated to shoot apex sink strength, which occurred at the expense of the cluster

Changes in Within-Shoot Carbon Partitioning in Pinot Noir Grapevines Subjected to Early Basal Leaf Removal

Early leaf removal significantly alters the source-sink balance within grapevine shoots, leading to a reduction in fruit set. However, no research has previously examined the conditions controlling this process in terms of carbon allocation among major sink organs following defoliation. In this study, the impact of defoliation at bloom on the distribution dynamics of leaf assimilates among clusters and growing shoot apices was investigated on Vitis vinifera, cv. Pinot noir, grown in Michigan, a cool climate viticultural region. Three levels of defoliation: no leaves removed (LR-0); six leaves removed from six basal nodes (LR-6); and ten leaves removed from ten basal nodes (LR-10), were imposed at full bloom. A 13C pulsing was performed 1 week after the treatment application to the defoliated shoots. Single leaf gas exchange (Pn), diurnal changes of the leaf net CO2 assimilation rate, carbon distribution, fruit-set, yield, and fruit composition were measured. Higher Pn was recorded in diurnal measurements of gas exchange in leaf removal (LR) treatments compared to LR-0. The shoot apex of LR-10 experienced the highest 13C allocation (%) after 3 and 7 days following the carbon pulsing. LR-10 had lower percentage of 13C allocated to clusters, which decreased fruit set by 60%, compared to the control, and enhanced the concentration of phenolic compounds in fruit. Alteration of carbon portioning among shoot sink organs indicated that an increasing severity of leaf removal significantly reduced fruit set, and was linearly correlated to shoot apex sink strength, which occurred at the expense of the cluster

Effects of a new arbuscular mycorrhizal fungus (Glomus iranicum) on grapevine development

During the spring of 2016, one-year-old own-rooted and 3-year-old grafted vines of cv. Sangiovese were treated with MycoUp, a formulation based on a recently identified mycorrhizal fungus, Glomus iranicum var. tenuihypharum sp. nova. The results are showing an impact on the development of the root system of the two different vine groups. The treated root systems were more expanded and able to explore a higher volume of soil. We observed a significant increase in total root volume and the volume of the soil explored by the entire root system, suggesting a more efficient use of water and nutrients, phosphorus in particular, with the potential of better overcoming periods of water stress

Cover Crop and Pruning Residue Management to Reduce Nitrogen Mineral Fertilization in Mediterranean Vineyards

This paper aimed to study the effect of temporary cover crop and vine pruning residue burial as alternative practices to conventional tillage on soil nitrate (NO3-N) availability and grapevine performance in the short term. The trial was carried out in a rain-fed vineyard (Vitis vinifera L., cv Grecanico dorato/140 Ruggeri) located in a traditional Mediterranean viticultural area (37320480 0 N; 13000150 0 E) in Sicily (Italy). Conventional tillage (CT) soil management was compared with winter cover crop (CC), conventional tillage plus buried pruning residue (CT + PR), and winter cover crop plus buried pruning residue (CC + PR) management treatments. Two fertilizer treatments (92 kg ha1 of N as urea and 0 kg ha1) were applied to the four soil management treatments. Vicia faba L. was the selected leguminous cover crop species, which was seeded in autumn and buried in spring at the same time as vine pruning residues. The soil NO3-N content was monitored, and vine vegetative growth, yield, and must quality were assessed over two seasons. Results showed that NO3-N availability strongly differed between fertilized (F) and unfertilized (UF) plots and years and among treatments. A positive effect of winter leguminous CC + PR on the Grecanico dorato grapevine performance was observed. In the UF vineyard, grape fertility, yield, Ravaz index, and total soluble solids were significantly higher in CC + PR vines than in other treatments, thus showing the reliability of reducing N mineral fertilization and related risks of excess nitrate in groundwater. The possibility of increasing the overall sustainability of rain-fed vineyards in a semiarid agro-ecosystem, without negative effects on grape and must quality, is also demonstrated

Effects of limited irrigation water volumes on near-isohydric ‘Montepulciano’ vines trained to overhead trellis system

The thermal increase, due to the changed climatic context, is leading to marked variations in the yield and quality of the grapes and causing an increase in the use of water resources in several viticultural areas. Nevertheless, in some environments, rainfalls are scarce and there is no water availability. In this study, we compared the impact of low water irrigation volumes (DI, replacement of 70% of crop evapotranspiration) with respect to non-irrigated vines (NI), on the physiological, yield and qualitative performances of near-isohydric variety ‘Montepulciano’, trained to overhead trellis system, which requires a high-water supply. The stomatal conductance and photosynthesis values, in basal and median leaves, were higher in DI vines. All NI leaves sufered water stress, showing in the youngest leaves (position 20 and 25 along the main shoot) higher carbon isotope discrimination (δ13C) (− 25.38‰ and 25–25.77‰, respectively). At harvest, DI vines showed yield higher of 30% and 33% than NI vines in 2005 and 2006, respectively, and 18% in 2007. In environments with prolonged water shortage and low water resource, near-isohydric ‘Montepulciano’ vines, trained to overhead trellis system and irrigated with limited volumes, determined a signifcant improvement of ‘vineyard efciency’ with a yield of 19.2 t/ha with respect to 13.4 t/ha of NI vines, ensuring also more sugar content (+31%), anthocyanin concentration (+13%) and polyphenolic substances (+8%) than NI vines

Unmanned Aerial Vehicle (UAV)-based remote sensing to monitor grapevine leaf stripe disease within a vineyard affected by esca complex

Foliar symptoms of grapevine leaf stripe disease (GLSD, a disease within the esca complex) are linked to drastic alteration of photosynthetic function and activation of defense responses in affected grapevines several days before the appearance of the first visible symptoms on leaves. The present study suggests a methodology to investigate the relationships between high-resolution multispectral images (0.05 m/pixel) acquired using an Unmanned Aerial Vehicle (UAV), and GLSD foliar symptoms monitored by ground surveys. This approach showed high correlation between Normalized Differential Vegetation Index (NDVI) acquired by the UAV and GLSD symptoms, and discrimination between symptomatic from asymptomatic plants. High-resolution multispectral images were acquired during June and July of 2012 and 2013, in an experimental vineyard heavily affected by GLSD, located in Tuscany (Italy), where vines had been surveyed and mapped since 2003. Each vine was located with a global positioning system, and classified for appearance of foliar symptoms and disease severity at weekly intervals from the beginning of each season. Remote sensing and ground observation data were analyzed to promptly identify the early stages of disease, even before visual detection. This work suggests an innovative methodology for quantitative and qualitative analysis of spatial distribution of symptomatic plants. The system may also be used for exploring the physiological bases of GLSD, and predicting the onset of this disease.