Double-Pruning: preventive technique against spring frost damage

The double pruning technique on Sangiovese vines, based on pre-pruning in February and finishing in April, induced a delay of bud break, which is an approach to avoid spring frost damage. The field experiment was conducted on Sangiovese vines mechanically spur-pruned during dormancy in February and manually finished post budburst to test the potential of ‘double-pruning’ approach to prevent the spring frost damage. This technique, associated with the finishing performed when the apical shoots on the mechanically-shortened canes were about 10 cm long, allowed to keep the basal buds in a dormant phase for almost 15 days, extending the resistance period against the spring frosts, particularly important for the cultivars characterized by early bud-break. Yield reduction per vine was -22% due only to the incidence of unsprouted buds, while the grape ripening profile was delayed with an increase of acidity and phenols and a decrease of pH and soluble solids.

The Decrease of Leaf Dark Respiration during Water Stress Is Related to Leaf Non-Structural Carbohydrate Pool in Vitis vinifera L

Dark respiration (R_d) is a fundamental plant process used to gain biomass and maintain plant physiological activity. It accounts for the metabolization of a large share of the carbon fixed by photosynthesis. However, R_d during conditions of severe plant water stress is still poorly understood. The decrease in leaf transpiration increases temperature, one of the most important drivers of leaf R_d. On the other hand, water stress decreases the pool of leaf carbohydrates, which are the most important substrate for respiration. The aim of the present work was to determine the impact of water shortage on leaf R_d in grapevine and understand the driving factors in modulating leaf R_d response under plant water stress conditions. Water stressed vines had lower R_d as the water shortage severity increased. R_d was correlated with leaf temperature in well-watered vines. Instead, in water stressed vines, R_d correlated with leaf soluble sugars. The decrease of leaf R_d in water stressed vines was due to the decrease of leaf non-structural carbohydrate that, under water stress conditions, exerted a limiting effect on R_d.

Kaolin Reduces ABA Biosynthesis Through the Inhibition of Neoxanthin Synthesis in Grapevines Under Water Deficit

In many viticulture regions, multiple summer stresses are occurring with increased frequency and severity because of warming trends. Kaolin-based particle film technology is a technique that can mitigate the negative effects of intense and/or prolonged drought on grapevine physiology. Although a primary mechanism of action of kaolin is the increase of radiation reflection, some indirect effects are the protection of canopy functionality and faster stress recovery by abscisic acid (ABA) regulation. The physiological mechanism underlying the kaolin regulation of canopy functionality under water deficit is still poorly understood. In a dry-down experiment carried out on grapevines, at the peak of stress and when control vines zeroed whole-canopy net CO₂ exchange rates/leaf area (NCER/LA), kaolin-treated vines maintained positive NCER/LA (~2 µmol m^-2 s^-1) and canopy transpiration (E) (0.57 µmol m^-2 s^-1). Kaolin-coated leaves had a higher violaxanthin (Vx) + antheraxanthin (Ax) + zeaxanthin (Zx) pool and a significantly lower neoxanthin (Nx) content (VAZ) when water deficit became severe. At the peak of water shortage, leaf ABA suddenly increased by 4-fold in control vines, whereas in kaolin-coated leaves the variation of ABA content was limited. Overall, kaolin prevented the biosynthesis of ABA by avoiding the deviation of the VAZ epoxidation/de-epoxidation cycle into the ABA precursor (i.e., Nx) biosynthetic direction. The preservation of the active VAZ cycle and transpiration led to an improved dissipation of exceeding electrons, explaining the higher resilience of canopy functionality expressed by canopies sprayed by kaolin. These results point out the interaction of kaolin with the regulation of the VAZ cycle and the active mechanism of stomatal conductance regulation.

Metabolic and transcriptional changes associated with the use of Ascophyllum nodosum extracts as tools to improve the quality of wine grapes (Vitis vinifera cv. Sangiovese) and their tolerance to biotic stress

BACKGROUND

Recent studies report that Ascophyllum nodosum extracts, once applied on the canopy of different crops, deliver positive effects, increasing yield, inducing tolerance to biotic stress, and improving the quality of products. However, the mechanisms of action are still unclear. In this research, vines subjected to multiple foliar applications of an A. nodosum extract (ANE) at label doses were compared with untreated vines (NTV) in accordance with a comparative approach. The investigation coupled a field experiment with a second trial conducted under semi-controlled conditions, to clarify the mechanisms of action involved.

RESULTS

The biostimulant did not affect soluble solids or the acidity of grapes; instead, it improved their anthocyanin and phenolic concentrations and the respective profiles. At the time of harvest, anthocyanin, and phenolic concentration were increased by 10.4% and 14.5%, respectively, when compared to the NTV. These effects correlated with a specific modulation of genes involved in the flavonoid metabolic pathways. Moreover, grapes from ANE vines witnessed a significant reduction in the spreading of gray mold when they were either assessed in field conditions or in vitro, compared to the grapes of NTV vines. This was related to a significant upregulation of the defense-related genes of the plant.

CONCLUSIONS

Overall, the results showed that A. nodosum extracts can be valuable tools in viticulture considering the emergence of challenging environmental conditions; hence, the regulation of specific metabolic pathways is the mechanism of action that leads to an increased tolerance of biotic stress and of changes in the content of grape metabolites. © 2019 Society of Chemical Industry.

Understanding kaolin effects on grapevine leaf and whole-canopy physiology during water stress and re-watering

Kaolin applications have been investigated in grapevines to understand cooling effects on leaves and clusters and the relative impact on gas exchange, leaf biochemistry, water use efficiency, glyco-metabolism and hormonal patterns. Several Almost all previous contributions have relied upon single-leaf measurements, leaving uncertainty on whole canopy performances, depending on the complexity of a canopy system vs. individual leaves. In our study, kaolin was sprayed at pre-veraison (DOY 204) on potted mature vines (cv. Sangiovese) and washed off a month later (DOY 233), while control vines were left unsprayed. Within control (C) and kaolin (KL) treated vines, well-watered (WW) and water stress (WS) treatments were also imposed over a 10-day period (DOY 208-217) and all vines were re-watered when the WS reached its peak (stem water potential between -1.3 and -1.6 MPa). Single leaf measurements included leaf surface temperature by thermal imaging (Leaf T_mean), assimilation (Leaf A), transpiration (Leaf E), stomatal conductance (Leaf g_s) rates, F_v/F_m fluorescence ratio, pre-dawn and stem water potential. Concurrently, whole canopy gas exchange was monitored continuously from DOY 200-259 using a vine enclosure system and daily net CO₂ exchange rate (NCER) and canopy transpiration (E_canopy) were calculated and then normalized vs. leaf area per vine. Results report that for any of the parameters recorded at both levels (single leaf and whole canopy), there was good agreement in terms of relative changes. In absence of water stress, KL was able to improve leaf cooling, while slightly reducing photosynthetic and water loss rates. More interestingly, data taken under water deficit and upon re-watering support the hypothesis that KL can turn into a protective agent for leaf function. In fact, the lack of photo-inhibition and the maintenance of leaf evaporative cooling found in KL-WS at the peak of water-stress (F_v/F_m > 0.7, Leaf T_mean < 38°C and E_canopy > 0.5mmol m^-2 s^-1) warranted a prompter recovery of leaf functions upon re-watering that did not occur in C-WS vines.

Kaolin treatments on Pinot noir grapevines for the control of heat stress damages

The aim of the study was to verify if vineyard kaolin application during the 2017 hot summer could reduce the negative effects of high temperatures and heat stress on canopy physiological processes, yield and fruit quality. The kaolin was applied once at the beginning of August, at 3% concentration, in a Pinot Noir vineyard. The application was performed only to the west side of the rows, where the vines were more subjected to heat stress. The 2017 summer was very hot, with maximum air temperature higher than 35 °C for several consecutive days in June, July and August and with heat waves that reached 42.3 °C in August. The kaolin coating works by significantly reducing leaf temperatures in comparison to untreated vines, with an average of about − 4 °C and up to −6 °C. Moreover, it maintains high the photosynthetic activity preventing irreversible photoinhibition phenomena, whereas untreated vines exhibit a marked physiological damage with chlorotic and necrotic leaves, dehydrated berries and sunburn damages. At harvest, 30-35% of the untreated vines were affected by severe water stress symptoms and produced unmarketable fruits. In comparison to the untreated vines, those sprayed with kaolin showed a higher yield (+27%), higher anthocyanins (+35%) and higher concentration of organic acids (+11%)

Vegetative development and berry growth in relation to heat accumulation in Sangiovese vines subjected to double pruning at three different times

The double pruning on Sangiovese based on pre-pruning and finishing in March, April and May applied over three years, induced a postponement of phenological phases, with repercussions on the vine vegetative and berry growth trends, with greater effects, according to the delay in the time of hand follow up during the season. The phenological development, the canopy and berry growth of Sangiovese, subjected to the three different finishing dates for the final pruning, were recorded during three years (2014-2016) and related to day of the year (DOY) and seasonal heat accumulation (growing degree days, GDD). A sigmoid growth model with high coefficient determination (R2 between 0.96 and 0.99), described shoot elongation and herbaceous berry growth, showing a temporal and thermal shift according to the finishing times. Despite the chronological delay, the vines revealed similar thermal necessities. Leaf area evolution of April and May finished vines showed 2 steps: a slow initial development followed by a rapid growth phase (91- 97cm2/GDD) beginning when shoots reached 7–10 leaves. GDD allowed to obtain simple models of vegetative development and berry growth of Sangiovese vines based on thermal evolution.

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.

Carbon partitioning between shoot organs following early leaf removal

In grapevines, basal leaf removal at bloom often induces a reduction of fruit set. The effect is related to a reduction in carbon availability for different plant organs competing for photosynthates. To understand and quantify carbon allocation among major sink organs following the early basal leaf removal, the effect of early basal defoliation was studied in Pinot noir grapevines. The experiment was performed in Michigan, a cool climate viticultural region, and three levels of defoliation were imposed at full bloom: (1) no leaves removed (DF-0); (2) six leaves removed from six basal nodes (DF-6); and (3) ten leaves removed from ten basal nodes (DF-10). A week after the defoliation treatment, 13C pulsing was executed to the defoliated shoots. Photosynthesis (Pn), carbon distribution, fruit set, vine performance and basic fruit composition were measured. LR treatments induced higher Pn when compared to LR-0. The highest 13C allocation (%) was recorded in the shoot apex of the LR-10 treatment and LR-10 had the lowest percentage of 13C transported to the cluster, with a reduced fruit set of about 60% when compared to LR-0. The severity of leaf removal reduced significantly fruit set and increased shoot apex sink strength 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.

Nebulized water cooling of the canopy affects leaf temperature, berry composition and wine quality of Sauvignon blanc

BACKGROUND

The present paper details a new technique based on spraying nebulized water on vine canopy to counteract the negative impact of the current wave of hot summers with temperatures above 30 °C, which usually determine negative effects on vine yield, grape composition and wine quality.

RESULTS

The automatized spraying system was able to maintain air temperature at below 30 °C (the threshold temperature to start spraying) for all of August 2013, when in the canopy of uncooled vines the temperature was as high as 36 °C. The maintenance of temperature below 30 °C reduced leaf stress linked to high temperature and irradiance regimes as highlighted by the decrease of H₂ O₂ content and catalase activity in the leaves. A higher amount of total polyphenols and organic acids and lower sugars characterized the grapes of cooled vines. Wine from these grapes had a higher content of some volatile thiols like 3-sulfanylhexanol (3SH) and 3-sulfanylhexylacetate (3SHA), and lower content of 4-methyl-4-sulfanylpentan-2-one (4MSP).

CONCLUSION

Under conditions of high temperature and irradiance regimes, water nebulization on the vine canopy can represent a valid solution to reduce and/or avoid oxidative stress and associated effects in the leaves, ensure a regular berry ripening and maintain high wine quality. The consumption of water during nebulization was acceptable, being 180 L ha^-1 min^-1 , which lasted an average of about 1 min to reduce the temperature below the threshold value of 30 °C. A total of 85-90 hL (from 0.8 to 0.9 mm) of water per hectare per day was required. © 2016 Society of Chemical Industry.

Transcriptional Responses to Pre-flowering Leaf Defoliation in Grapevine Berry from Different Growing Sites, Years, and Genotypes

Leaf removal is a grapevine canopy management technique widely used to modify the source-sink balance and/or microclimate around berry clusters to optimize fruit composition. In general, the removal of basal leaves before flowering reduces fruit set, hence achieving looser clusters, and improves grape composition since yield is generally curtailed more than proportionally to leaf area itself. Albeit responses to this practice seem quite consistent, overall vine performance is affected by genotype, environmental conditions, and severity of treatment. The physiological responses of grape varieties to defoliation practices have been widely investigated, and just recently a whole genome transcriptomic approach was exploited showing an extensive transcriptome rearrangement in berries defoliated before flowering. Nevertheless, the extent to which these transcriptomic reactions could be manifested by different genotypes and growing environments is entirely unexplored. To highlight general responses to defoliation vs. different locations, we analyzed the transcriptome of cv. Sangiovese berries sampled at four development stages from pre-flowering defoliated vines in two different geographical areas of Italy. We obtained and validated five markers of the early defoliation treatment in Sangiovese, an ATP-binding cassette transporter, an auxin response factor, a cinnamyl alcohol dehydrogenase, a flavonoid 3-O-glucosyltransferase and an indole-3-acetate beta-glucosyltransferase. Candidate molecular markers were also obtained in another three grapevine genotypes (Nero d'Avola, Ortrugo, and Ciliegiolo), subjected to the same level of selective pre-flowering defoliation (PFD) over two consecutive years in their different areas of cultivation. The flavonol synthase was identified as a marker in the pre-veraison phase, the jasmonate methyltransferase during the transition phase and the abscisic acid receptor PYL4 in the ripening phase. The characterization of transcriptome changes in Sangiovese berry after PFD highlights, on one hand, the stronger effect of environment than treatment on the whole berry transcriptome rearrangement during development and, on the other, expands existing knowledge of the main molecular and biochemical modifications occurring in defoliated vines. Moreover, the identification of candidate genes associated with PFD in different genotypes and environments provides new insights into the applicability and repeatability of this crop practice, as well as its possible agricultural and qualitative outcomes across genetic and environmental variability.

Distinct transcriptome responses to water limitation in isohydric and anisohydric grapevine cultivars

BACKGROUND

Grapevine (Vitis vinifera L.) is an economically important crop with a wide geographical distribution, reflecting its ability to grow successfully in a range of climates. However, many vineyards are located in regions with seasonal drought, and these are often predicted to be global climate change hotspots. Climate change affects the entire physiology of grapevine, with strong effects on yield, wine quality and typicity, making it difficult to produce berries of optimal enological quality and consistent stability over the forthcoming decades.

RESULTS

Here we investigated the reactions of two grapevine cultivars to water stress, the isohydric variety Montepulciano and the anisohydric variety Sangiovese, by examining physiological and molecular perturbations in the leaf and berry. A multidisciplinary approach was used to characterize the distinct stomatal behavior of the two cultivars and its impact on leaf and berry gene expression. Positive associations were found among the photosynthetic, physiological and transcriptional modifications, and candidate genes encoding master regulators of the water stress response were identified using an integrated approach based on the analysis of topological co-expression network properties. In particular, the genome-wide transcriptional study indicated that the isohydric behavior relies upon the following responses: i) faster transcriptome response after stress imposition; ii) faster abscisic acid-related gene modulation; iii) more rapid expression of heat shock protein (HSP) genes and iv) reversion of gene-expression profile at rewatering. Conversely, that reactive oxygen species (ROS)-scavenging enzymes, molecular chaperones and abiotic stress-related genes were induced earlier and more strongly in the anisohydric cultivar.

CONCLUSIONS

Overall, the present work found original evidence of a molecular basis for the proposed classification between isohydric and anisohydric grapevine genotypes.

Phenology, Canopy Aging and Seasonal Carbon Balance as Related to Delayed Winter Pruning of Vitis vinifera L. cv. Sangiovese Grapevines

Manipulating or shifting annual grapevine growing cycle to offset limitations imposed by global warming is a must today, and delayed winter pruning is a tool to achieve it. However, no information is available about its physiological background, especially in relation to modifications in canopy phenology, demography and seasonal carbon budget. Mechanistic hypothesis underlying this work was that very late winter pruning (LWP) can achieve significant postponement of phenological stages so that ripening might occur in a cooler period and, concurrently, ripening potential can be improved due to higher efficiency and prolonged longevity of the canopy. Variability in the dynamics of the annual cycle was created in mature potted cv. Sangiovese grapevines subjected to either standard winter pruning (SWP) or late and very late winter pruning (LWP, VLWP) performed when apical shoots on the unpruned canes were at the stage of 2 and 7 unfolded leaves. Vegetative growth, phenology and canopy net CO2 exchange (NCER) were followed throughout the season. Despite LWP and VLWP induced a bud-burst delay of 17 and 31 days vs. SWP, the delay was fully offset at harvest for LWP and was reduced to 6 days in VLWP. LWP showed notably higher canopy efficiency as shorter time needed to reach maximum NCER/leaf area (22 days vs. 34 in SWP), highest maximum NCER/leaf area (+37% as compared to SWP) and higher NCER/leaf area rates from veraison to end of season. As a result, seasonal cumulated carbon in LWP was 17% higher than SWP. A negative functional relationship was also established between amount of leaf area removed at winter pruning and yield per vine and berry number per cluster. Although retarded winter pruning was not able to postpone late-season phenological stages under the warm conditions of this study, it showed a remarkable potential to limit yield while improving grape quality, thereby fostering the hypothesis that it could be used to replace time-consuming and costly cluster thinning. This preliminary study indicates that proper winter pruning date should be timed so as not to exceed the stage of two unfolded leaves.

Influence of light and shoot development stage on leaf photosynthesis and carbohydrate status during the adventitious root formation in cuttings of Corylus avellana L

Adventitious root formation in plant cuttings is influenced by many endogenous and environmental factors. Leaf photosynthesis during rooting of leafy cuttings in hard to root species can contribute to supply carbohydrates to the intensive metabolic processes related to adventious root formation. Light intensity during rooting is artificially kept low to decrease potential cutting desiccation, but can be limiting for photosynthetic activity. Furthermore, leafy cuttings collected from different part of the shoot can have a different ability to fuel adventitious root formation in cutting stem. The aim of this work was to determine the role of leaf photosynthesis on adventitious root formation in hazelnut (Corylus avellana L) (a hard-to-root specie) leafy cuttings and to investigate the possible influence of the shoot developmental stage on cutting rooting and survival in the post-rooting phase. Cutting rooting was closely related to carbohydrate content in cutting stems during the rooting process. Cutting carbohydrate status was positively influenced by leaf photosynthesis during rooting. Non-saturating light exposure of leafy cuttings can contribute to improve photosynthetic activity of leafy cuttings. Collection of cuttings from different part of the mother shoots influenced rooting percentage and this appear related to the different capability to concentrate soluble sugars in the cutting stem during rooting. Adventitious root formation depend on the carbohydrate accumulation at the base of the cutting. Mother shoot developmental stage and leaf photosynthesis appear pivotal factors for adventitious roots formation.

Physiological parameters and protective energy dissipation mechanisms expressed in the leaves of two Vitis vinifera L. genotypes under multiple summer stresses

Photosynthetic performances and energy dissipation mechanisms were evaluated on the anisohydric cv. Sangiovese and on the isohydric cv. Montepulciano (Vitis vinifera L.) under conditions of multiple summer stresses. Potted vines of both cultivars were maintained at 90% and 40% of maximum water availability from fruit-set to veraison. One week before veraison, at predawn and midday, main gas-exchange and chlorophyll fluorescence parameters, chlorophyll content, xanthophyll pool and cycle and catalase activity were evaluated. Under water deficit and elevated irradiance and temperature, contrary to cv. Montepulciano and despite a significant leaf water potential decrease, Sangiovese's leaves kept their stomata more open and continued to assimilate CO2 while also showing higher water use efficiency. Under these environmental conditions, in comparison with the isohydric cv. Montepulciano, the protective mechanisms of energy dissipation exerted by the anisohydric cv. Sangiovese were: (i) higher stomatal conductance and thermoregulation linked to higher transpiration rate; (ii) greater ability at dissipating more efficiently the excess energy via the xanthophylls cycle activity (thermal dissipation) due to higher VAZ pool and greater increase of de-epoxidation activity.

Stomatal closure is induced by hydraulic signals and maintained by ABA in drought-stressed grapevine

Water saving under drought stress is assured by stomatal closure driven by active (ABA-mediated) and/or passive (hydraulic-mediated) mechanisms. There is currently no comprehensive model nor any general consensus about the actual contribution and relative importance of each of the above factors in modulating stomatal closure in planta. In the present study, we assessed the contribution of passive (hydraulic) vs active (ABA mediated) mechanisms of stomatal closure in V. vinifera plants facing drought stress. Leaf gas exchange decreased progressively to zero during drought, and embolism-induced loss of hydraulic conductance in petioles peaked to ~50% in correspondence with strong daily limitation of stomatal conductance. Foliar ABA significantly increased only after complete stomatal closure had already occurred. Rewatering plants after complete stomatal closure and after foliar ABA reached maximum values did not induced stomatal re-opening, despite embolism recovery and water potential rise. Our data suggest that in grapevine stomatal conductance is primarily regulated by passive hydraulic mechanisms. Foliar ABA apparently limits leaf gas exchange over long-term, also preventing recovery of stomatal aperture upon rewatering, suggesting the occurrence of a mechanism of long-term down-regulation of transpiration to favor embolism repair and preserve water under conditions of fluctuating water availability and repeated drought events.

Relationships between stomatal behavior, xylem vulnerability to cavitation and leaf water relations in two cultivars of Vitis vinifera

Current understanding of physiological mechanisms governing stomatal behavior under water stress conditions is still incomplete and controversial. It has been proposed that coordination of stomatal kinetics with xylem vulnerability to cavitation [vulnerability curve (VC)] leads to different levels of isohydry/anisohydry in different plant species/cultivars. In this study, this hypothesis is tested in Vitis vinifera cultivars displaying contrasting stomatal behavior under drought stress. The cv Montepulciano (MP, near-isohydric) and Sangiovese (SG, anisohydric) were compared in terms of stomatal response to leaf and stem water potential, as possibly correlated to different petiole hydraulic conductivity (k(petiole)) and VC, as well as to leaf water relations parameters. MP leaves showed almost complete stomatal closure at higher leaf and stem water potentials than SG leaves. Moreover, MP petioles had higher maximum k(petiole) and were more vulnerable to cavitation than SG. Water potential at the turgor loss point was higher in MP than in SG. In SG, the percentage reduction of stomatal conductance (PLg(s)) under water stress was almost linearly correlated with corresponding percentage loss of k(petiole) (PLC), while in MP PLg(s) was less influenced by PLC. Our results suggest that V. vinifera near-isohydric and anisohydric genotypes differ in terms of xylem vulnerability to cavitation as well as in terms of k(petiole) and that the coordination of these traits leads to their different stomatal responses under water stress conditions.

Morpho-structural and physiological response of container-grown Sangiovese and Montepulciano cvv. (Vitis vinifera) to re-watering after a pre-veraison limiting water deficit

A better physiological and productive performance of cv. Montepulciano versus cv. Sangiovese under well-watered conditions has been recently assessed. The objective of this study was to verify that this behaviour is maintained when a pre-veraison deficit irrigation (vines held at 40% pot capacity from fruit-set to veraison) followed by re-watering (pot capacity reported at 90%). Single leaf assimilation rate and stomatal conductance, diurnal and seasonal whole-canopy net CO2 exchange (NCER) and water use efficiency were always higher in Sangiovese under deficit irrigation. Due to water shortage Montepulciano displayed a more compact growing habit due to decreased shoot and internode length. Sangiovese showed excellent recovery upon re-watering as NCER resulted to be higher than the pre-stress period; however, this might also relate to early and severe basal leaf yellowing and shedding. Early deficit irrigation affected xylem characteristics of Montepulciano more than in Sangiovese; vessel density increased (37 vs 29%, respectively, compared with well-watered vines) and the hydraulic conductance decreased more (-13 vs -3% respectively) compared with well-watered vines. Yield components and technological maturity were similar in the two cultivars, whereas Montepulciano grapes had lower anthocyanins and phenolics. Higher physiological and productive efficiency under non-limiting water conditions showed by Montepulciano compared with Sangiovese was basically reversed when both cultivars were subjected to an early deficit irrigation.

Is stored malate the quantitatively most important substrate utilised by respiration and ethanolic fermentation in grape berry pericarp during ripening?

A widely held view is that in grape pericarp glycolysis is inhibited during ripening, and that stored malate rather than sugars become the major substrate for respiration. In this study we determined what contribution stored malate could make to the substrate requirements of respiration and ethanolic fermentation in the pericarp of Cabernet Sauvignon berries during ripening. At a number of time points through development the amount of malate in the pericarp was measured. The change in malate content between each time point was then calculated, having first allowed for dilution arising from expansion of the fruit. The amount of CO2 that was released by the berry in the interval between each pair of time points was measured. It was found that the contribution that stored malate could make to the substrate requirements of respiration and ethanolic fermentation of grape pericarp was dependent on the stage of ripening. At the beginning of ripening stored malate could provide a greater proportion of substrate than later in ripening, and during the latter its contribution was relatively low. Therefore, stored malate was not the quantitatively most important substrate utilised by respiration and ethanolic fermentation in the pericarp of grape berries during most of ripening. It is likely that sugars provide the bulk of the deficit in substrate. Further, the increase in the respiratory quotient during most of ripening does not arise from the use of malate as main respiratory substrate.

Morpho-structural and physiological performance of Sangiovese and Montepulciano cvv. (Vitis vinifera) under non-limiting water supply conditions

Morpho-structural and physiological traits of Sangiovese and Montepulciano varieties (Vitis vinifera L. - two red grapes widely cultivated in Italy), grown outside under non-limiting water supply conditions were evaluated in 2007 and 2008 and results were correlated with yield components and grape composition. The 2-year analysis showed intraspecific differences in canopy characteristics, leaf and shoot properties, photosynthetic ability, water use efficiency, vine yield and grape composition. Compared with Sangiovese, Montepulciano was able to assure a higher whole-canopy seasonal net CO2 exchange rate during the season (+38% in mid morning and +49% in mid afternoon). It also had higher water use efficiency (especially early in the morning and in late afternoon) and a higher vine yield (+16%). Furthermore, total soluble solids (+1.7 °Brix), anthocyanins (+0.44mgcm-2 berry skin) and phenolic compounds (+0.88mgcm-2 berry skin) were higher in the grapes. To ensure this performance, Montepulciano vines have to support higher costs of growth and maintenance processes, made possible because of the increased respiration activity of the canopy during the night. We confirmed that vine yield and grape composition is strictly dependent on the seasonal photosynthetic capacity of the canopy. Therefore, Montepulciano should be put in a position to fully realise this substantial photosynthetic potential, by avoiding or reducing environmental stress. Sangiovese is structurally and morpho-physiologically better able to withstand any stress during the summer than Montepulciano. Sangiovese xylem tissue had larger mean vessel density and smaller mean vessel diameter and hydraulic conductance than Montepulciano, holding the hypothesis of less susceptibility to conduit damage.

Adequacy and nutrition in the absence of residual renal function in peritoneal dialysis

With the aim of evaluating nutrition indices and dialysis adequacy level in patients who started peritoneal dialysis (PD) without residual renal function, we retrospectively studied 19 patients [8 men, 11 women; 3 with diabetes (15.8%); mean age: 44.5 +/- 10.74 years; 15 on continuous ambulatory peritoneal dialysis (CAPD), 3 on continuous cycling peritoneal dialysis (CCPD), 1 on nightly intermittent peritoneal dialysis (NIPD)]. The mean time spent by these patients on hemodialysis before PD was 62.7 +/- 54.7 months (range: 8.8-216 months), and the mean time on PD was 46.2 +/- 21.4 months (range: 10-75 months). In these patients, we measured weekly Kt/V urea, weekly creatinine clearance (CrC), normalized protein catabolic rate (nPCR), body surface area (BSA), urea distribution volume (V), serum albumin, body mass index (BMI), percent lean body mass (%LBM), infusion volume (liters per day), subjective global assessment (SGA), and peritoneal equilibration test (PET). Using the Student t-test at a significance level of p < 0.05, we compared initial body weight (INW), actual weight (AW), and ideal body weight (IBW) according to age, sex, and height. We analyzed actuarial and technique survival (Kaplan-Meier). In regard to patient survival, only death was considered the end point; for technique survival, only technique failure was considered the end point. Data are expressed as mean +/- standard deviation. Results were: Kt/V, 2.20 +/- 0.46 L weekly; CrC, 59.11 +/- 12 L weekly; nPCR, 1.08 +/- 0.25 g/kg daily; BSA, 1.67 +/- 0.2 m2; V, 33.34 +/- 7.12; serum albumin, 3.68 +/- 0.22 g/dL; BMI, 24.06 +/- 4.16; %LBM, 64.92 +/- 10.13; SGA, 94.7% well-nourished; AW, 65.37 +/- 13.88 kg; IBW, 67.21 +/- 10.5 kg (AW vs IBW: r = 0.69, p > 0.05); INW, 61.54 +/- 11.07 kg (INW vs AW: r = 0.92, p < 0.05; INW vs IBW: r = 0.71, p < 0.05). Distribution of transport status by PET was 15.8% high transport, 36.8% high-average transport, 36.8% low-average transport, and 10.5% low transport. Mean infusion volume was 10.41 +/- 1.36 L in 24 hours. Cumulative survival was 100%, 98%, and 82% after 1, 2, and 6 years respectively. Technique survival was 100% after 6 years. The adequacy results accord with Dialysis Outcomes Quality Initiative (DOQI) recommendations, and the nutrition indices and actuarial and technique survival are satisfactory for anuric patients.