Vine Biomass Research Articles

Purification of stilbenes from grape stems in a continuous process based on photo-molecularly imprinted adsorbents and hydroalcoholic solvents

This study presents a sustainable method to purify stilbenes from residual grape stem biomass. This approach was experimentally validated through the use of a pilot size fixed-bed adsorption prototype for the automation of the purification process. Molecularly imprinted polymers, synthesized through photopolymerization at room temperature and incorporating the 4-vinylpyridine monomer, serve as adsorbents. The purification procedure leads to a significant enrichment, with a more than 22-fold increase in (E)-ε-viniferin and a 9-fold increase in (E)-resveratrol. High recoveries of 80.3% and 62.1% for (E)-ε-viniferin and (E)-resveratrol, respectively, were achieved. Notably, the use of eco-friendly water and ethanol mixtures distinguishes this method from others focused on stilbenes purification. This study further explores the variability of the stilbenes in the residual grape stems by analysing different varieties, emphasizing the complexity of the starting material of the purification process. The range of purities achieved for the fractions enriched with stilbenes (e.g., 12.8% for (E)-ε-viniferin and 3.4% for (E)-resveratrol) are suitable for direct use in controlling of Plasmopara viticola, the agent causing grapevine downy mildew. Furthermore, through compositional combination of these fractions, it is possible to conceive new stilbene-containing phytochemicals with improved anti-fungal activity. Therefore, the developed adsorbents and purification process, enabling the steady enrichment of stilbenes regardless of the unavoidable variability in the initial vine biomass, is a contribution towards the quest for more environmentally friendly and sustainable phytochemicals.

Grafting Genotype Combination Effect of Vitis ssp. on Roots Phylloxeration Degree and Vigor of Grapevine

The present study investigated whether different grafting combinations (hypobiont-epibiont) of Vitis spp. influence root infection with phylloxera and thus vine biomass on potted 2-year-old plants. The study was conducted simultaneously at two locations in Slovenia (VEM) and Hungary (GF). The dormant canes of ‘Johanniter’ (JOH), ‘Riesling’ (RR) and Vitis berlandieri × Vitis riparia ‘Teleki 5C’ (5C) were hetero-grafted (each with each) and autografted (each with itself), so that nine plant combinations were used for the trial. The roots of the experimental plants at different ages (1–2 years) were infested with two phylloxera populations originating from two locations (VEM, GF). Plant growth was quantified 120 days after inoculation by measuring root and shoot biomass, while the extent of phylloxera infestation was assessed by the number of feeding sites (nodosities, tuberosities) and the number of larval stages of phylloxera. In most cases, the genotype of the hypobiont influenced the degree of phylloxera infestation on all roots of the two-year-old root system. At both locations, the highest number of nodosities and the highest increase in phylloxera population was observed on the autografted Teleki 5C (5C/5C). The phylloxera biotype derived from Vitis vinifera roots (GF) induced tuberosities, especially on roots of combinations where JOH and RR were used as hypobionts. No correlation was found between biomass and phylloxera infestation. The hypobiont genotype had no effect on cane biomass at the end of the growth cycle at either experimental site.

Dried tomato vines in substitution to alfalfa hay to feed Barbarine lambs: Effects on diet intake, growth performances and carcass quality

Tomato vines are a by-product of tomato plants pruning at different stage of growth and production. Large quantities of tomato vine biomass are produced and accumulated near greenhouses and cause environmental problems. Tomato vines could be used (DTV) as dry roughage to feed livestock. The objective of this study was to evaluate the effects of substituting dried tomato vines (DTV) to alfalfa hay at two levels (50% and 75%) on feed intake, growth performances, non-carcass components, and carcass characteristics of Barbarine lambs. Twenty four 8 months-old Barbarine lambs, with an average weight of 31 kg, were divided into three groups of 8 each and fed diets with different compositions of the roughage portion: the Al100 group received only alfalfa hay as forage, the Al50-T50 group received equal portions of alfalfa hay and DTV, and for the T75-Al25group, the roughage portion was composed of 75% of DTV and 25% of alfalfa hay. All lambs received the same amounts of forage (increasing from 1000 to 1400 g) and the same quantities of concentrated feed (increased from 500 to 700 g). The trial lasted 88 days, after which all of the animals were slaughtered. It was found that substituting DTV to alfalfa hay at the levelof 50% had no effect on roughage and total diet intake. In addition, DTV intake did not affect the slaughter weight (P > 0.05), although the average daily gain and total weight gain were 136 g and 11.5 kg for the Al100 and Al50-T50 groups vs. 125 g and 9.6 kg,; for the T75-Al25 group. Overall, carcass yields and non-carcass components were similar for the three groups of lambs. However, DTV incorporation at the levels of 50% and 75% resulted in leaner carcasses for both tomato groups compared with the Al100 group (54.3 vs.49.9% of muscle and 24.4 vs. 28.8% of fat, respectively). Nevertheless, the highest level of tomato incorporation (75%) promoted the development of the leaner second meat grade (SMCC)(18.2%; P = 0.02) compared to the medium (50%) and null level (0%) of DTV incorporation, which resulted in the same proportion of SMCC(17.5%).

Removal of pruned vine biomass (PVB) from vineyards – Examining the impact of not incorporating PVB into vineyard soils

The wine industry worldwide faces increasing challenges to achieve sustainable levels of carbon emission mitigation. This study seeks to establish the feasibility of harvesting winter pruned vineyard biomass (PVB) for potential use in carbon footprint reduction as a renewable biofuel for energy production. Of particular interest is the role PVB plays as a carbon source in vineyard soils and what effect annual removal might have on soil carbon. An investigation was carried out in the Coombe vineyard, Waite Campus (University of Adelaide), Australia. Vines are grown in a Vertic clay loam soil with well-managed mid-row swards in a temperate zone. A comparison was undertaken of two mid-row treatments after 13 years of consistent management: 1) the deliberate exclusion of PVB from every third row, and 2) in the remaining rows PVB was incorporated at an average of 3.4 and 5.5 t/ha in two 0.25 ha blocks containing Shiraz and Semillon respectively. In both 0-10 cm and 10-30 cm soil core sample depths, combined soil carbon % values in the desired range of 1.80 to 3.50 were not significantly different between treatments or cultivars and yielded an estimated 42 t/ha of soil carbon. Other key physical and chemical values were likewise not significantly different between treatments. Results suggest that in a temperate zone vineyard, managed such as the one used in this study, there is no long-term negative impact on soil carbon sequestration through removing PVB. This implies that growers could confidently harvest PVB for use in biofuel production.

Removal of methylene blue from aqueous solution using common bean vine and cowpea vine biomass

Removal of methylene blue from aqueous solution using common bean vine and cowpea vine biomass

Use of remote sensing-derived fPAR data in a grapevine simulation model for estimating vine biomass accumulation and yield variability at sub-field level

Grapevine simulation models are mostly used to estimate plant development, growth and yield at plot scale. However, the spatial variability of pedologic and micro-climatic conditions can influence vine growth, leading to a sub-field heterogeneity in plant vigor and final yield that may be better estimated through the assimilation of high spatial resolution data in crop models. In this study, the spatial variability of grapevine intercepted radiation at fruit-set was used as input for a grapevine simulation model to estimate the variability in biomass accumulation and yield in two Tuscan vineyards (Sites A and B). In Site A, the model, forced with intercepted radiation data as derived from the leaf area index (LAI), measured at canopy level in three main vigor areas of the vineyard, provided a satisfactory simulation of the final pruning weight (r2 = 0.61; RMSE = 19.86 dry matter g m−2). In Site B, Normalized Difference Vegetation Index (NDVI) from Sentinel-2A images was firstly re-scaled to account for canopy fraction cover over the study areas and then used as a proxy for grapevine intercepted radiation for each single pixel. These data were used to drive the grapevine simulation model accounting for spatial variability of plant vigor to reproduce yield variability at pixel scale (r2 = 0.47; RMSE = 75.52 dry matter g m−2). This study represents the first step towards the realization of a decision tool supporting winegrowers in the selection of the most appropriate agronomic practices for reducing the vine vigor and yield variability at sub-field level.

Effect of grafting and cover crop quality on nitrogen uptake from different pools by drip irrigated heirloom tomatoes in an open field trial

Fresh-market tomatoes (Lycopersicon esculentum Mill.) are increasingly produced with subsurface drip irrigation in California, as growers adapt to decreased water availability. Drip irrigation improves water use efficiency, but may reduce the soil volume where conditions are optimal for microbial and root activity. This poses complications for organic growers, whose cropping systems are dependent on microorganisms to convert the nitrogen (N) from organic sources into plant-available N. To investigate grafting as a potential practice to increase access to N, grafted and non-grafted “Brandywine” heirloom tomatoes were grown with drip irrigation in a two-year field trial. The three rootstocks were “Maxifort,” “Fortamino,” and “DRO138TX.” Prior to each growing season, a legume cover crop mix was grown and labeled with 15N ammonium sulfate to track tomato N uptake from cover crop residues. There were no significant differences in yield, N uptake and N partitioning in the plants due to rootstock treatments. Leaf analyses suggested that the tomato plants were not N deficient in either year. However, there was a significant difference in total N uptake from cover crop residues between years. This was caused by large differences in N concentration in the cover crop. Plants responded to a lower N availability by producing less vine biomass, while producing the same fruit yield. A budget revealed that the tomato plants accessed a considerable amount of N from the soil below 60 cm of the profile to cover their demand.

Nitrate Uptake and Transport Properties of Two Grapevine Rootstocks With Varying Vigor.

In viticulture, rootstocks are essential to cope with edaphic constraints. They can also be used to modulate scion growth and development to help improve berry yield and quality. The rootstock contribution to scion growth is not fully understood. Since nitrogen (N) is a significant driver of grapevine growth, rootstock properties associated with N uptake and transport may play a key role in the growth potential of grafted grapevines. We evaluated N uptake and transport in a potted system using two grapevines rootstocks [Riparia Gloire (RG) and 1103 Paulsen (1103P)] grafted to Pinot noir (Pommard clone) scion. Combining results of nitrate induction and steady-state experiments at two N availability levels, we observed different responses in the uptake and utilization of N between the two rootstocks. The low vigor rootstock (RG) exhibited greater nitrate uptake capacity and nitrate assimilation in roots after nitrate resupply than the more vigorous 1103P rootstock. This behavior may be attributed to a greater root carbohydrate status observed in RG for both experiments. However, 1103P demonstrated a higher N translocation rate to shoots regardless of N availability. These distinct rootstock behaviors resulted in significant differences in biomass allocation between roots and shoots under N-limited conditions, although the overall vine biomass was not different. Under sufficient N supply, differences between rootstocks decreased but 1103P stored more N in roots, which may benefit growth in subsequent growing seasons. Overall, greater transpiration of vines grafted to 1103P rootstock causing higher N translocation to shoots could partially explain its known growth-promoting effect to scions under low and high N availability, whereas the low vigor typically conferred to scions by RG may result from the combination of lower N translocation to shoots and a greater allocation of biomass toward roots when N is low.

Early vine harvesting of dual-purpose sweet potato (Ipomoea batatas) increases feeding quality and total biomass without comprising tuber production

Sweet potato is an important food crop throughout much of sub-Saharan Africa with the important attribute as a dual-purpose crop. While tuberous crops are grown for human consumption, the sweet potato can also provide substantial vine biomass suitable for feeding animals without competing for human feed resources. Sweet potato is generally low in nutrient other than carbohydrate. The newly developed orange-fleshed varieties of sweet potato, high in beta-carotene yield large quantities of vines with very little exploration of their agronomic attributes to date. Intermediate vine harvesting (ratooning) has been promoted as a strategy to further increase the value of sweet potato as a dual-purpose human/animal feed crop. The results of this practice on yields of other types of sweet potato have been equivocal or highly variable. Production effects on three new orange-fleshed dual-purpose sweet potato (Kenspot 1, SPK 013, SPK 117) developed by the International Potato Centre (CIP), of intermediate plus final (INT) versus final only (FIN) vine harvesting were assessed in a randomized block with a split plot trial. Cultivar SPK013 produced the greatest vine, tuber and total biomass yield of the three varieties tested, but also the greatest decline in tuber yields after intermediate vine harvesting. While intermediate harvesting increased vine yield in all varieties (p<0.05), in cultivar SPK013, it caused a 58% decline in tuber yield (p<0.05). The variation in performance between cultivars assessed in this study, reflects what is seen in the general literature. What is clear from the present study is that, there is a substantial interaction between environment/cultural practice and genotype. As such, it seems impossible to generalize that Intermediate vine harvesting is beneficial for vine production in the cultivars studied. It should be borne in mind that this practice may also be associated with a substantial decline in tuber yield in some cultivars. Thus, results should not be extrapolated to other varieties without investigation.

The simulation of the vine biomass at different planting ages in Ningxia vineyards using DNDC model

The vine total biomass of different planting ages from plants in vineyard (1–12 years) was investigated by analysing biomass in stands with various ages and also simulated using the denitrification-decomposition (DNDC) model in the east Helan Mountains, Ningxia in 2011. The results indicated that the DNDC model accurately simulated the total biomass at different planting ages in the studied vineyard; the simulated results were approximately 93.6% of the measured results, and the biomass determination coefficient R2 between the model simulation and the in situ observations was 0.948 (p < 0.01), representing a significant correlation. Under the simulation, the vine biomass accumulation was found to be sensitive to the changes of fertilisation depth, soil organic carbon content, pH and other factors, and would effectively increase by appropriate increase of the fertilisation amount and decrease of the irrigation amount at the same time. Therefore, the DNDC model is applicable for simulating biomass in Ningxia vineyards and it has the potential to be widely applied to assess crop biomass variations under different climate conditions or management methods.

Effect of leaching pretreatment on the gasification of wine and vine (residue) biomass

Utilization of biomass residues for energetic purposes increases the share of renewables in the total energy balance. Gasification is one of the thermochemical processes that converts solid biomass to valuable gaseous products. Prior to the gasification process, biomass material could be treated to improve the quality or composition of the product gas. Our focus is on fluidized bed gasification of untreated vine and pretreated vine residue and pretreated wine residue. Natural and artificial leaching were used as pretreatment methods. Our results showed that CO and H2 content in the product gas are higher in leached (16.9 and 10.0% respectively) vine residue than in untreated material (14.5 and 7.7% respectively). The naturally leached wine residue was found to have the highest CO content (18.1%) and relatively high H2 content (9.7%) in the product gas, but lower CH4 (1.0%) and CO2 content (5.6%). The results of tar measurements indicated that the leaching pre-treatment lowers the tar content in the evolved product gas, e.g. by 36% in the case of vine residues. As a result, the controlled leaching pretreatment is recommended as an effective way of upgrading the composition of agricultural biomass.

Allometric relationships for estimating vegetative and reproductive biomass in grapevine (Vitis viniferaL.)

Background and Aims Vineyards, one of the most widespread agricultural systems, have significant but scarcely evaluated carbon sequestration potential. Allometry is a cost-effective approach to estimate plant biomass, but few studies – focused mainly on permanent structure carbon fixation – have dealt with it in grapevine. This study develops allometric models that accurately estimate grapevine standing biomass (total vine biomass at harvest), using extensive field-collected data sets. Methods and Results Data were obtained in vineyards located in Spanish regions representative of the variability found in warm semi-arid Mediterranean regions. We developed and validated functions to estimate vine biomass for all vine organs. The models obtained estimated accurately the biomass fixed by each organ separately and even more accurately at the whole plant scale. To illustrate the potential of the models, they satisfactorily assessed the influence of seasonal vine water status on vine biomass production and partitioning using an independent data set. Conclusions and Significance of the Study The models constitute a powerful tool to determine in a non-destructive and cost-effective manner standing biomass from simple vine measurements, which makes them suitable for quantifying carbon stocks and allocation patterns, and for evaluating the influence of climate or cultural practices at large scale to estimate better – at a regional or international level – the contribution of grapevine culture to CO2 balances.

From berries to blocks: carbon stock quantification of a California vineyard

BackgroundQuantifying terrestrial carbon (C) stocks in vineyards represents an important opportunity for estimating C sequestration in perennial cropping systems. Considering 7.2 M ha are dedicated to winegrape production globally, the potential for annual C capture and storage in this crop is of interest to mitigate greenhouse gas emissions. In this study, we used destructive sampling to measure C stocks in the woody biomass of 15-year-old Cabernet Sauvignon vines from a vineyard in California’s northern San Joaquin Valley. We characterize C stocks in terms of allometric variation between biomass fractions of roots, aboveground wood, canes, leaves and fruits, and then test correlations between easy-to-measure variables such as trunk diameter, pruning weights and harvest weight to vine biomass fractions. Carbon stocks at the vineyard block scale were validated from biomass mounds generated during vineyard removal.ResultsTotal vine C was estimated at 12.3 Mg C ha−1, of which 8.9 Mg C ha−1 came from perennial vine biomass. Annual biomass was estimated at 1.7 Mg C ha−1 from leaves and canes and 1.7 Mg C ha−1 from fruit. Strong, positive correlations were found between the diameter of the trunk and overall woody C stocks (R2 = 0.85), pruning weights and leaf and fruit C stocks (R2 = 0.93), and between fruit weight and annual C stocks (R2 = 0.96).ConclusionsVineyard C partitioning obtained in this study provides detailed C storage estimations in order to understand the spatial and temporal distribution of winegrape C. Allometric equations based on simple and practical biomass and biometric measurements could enable winegrape growers to more easily estimate existing and future C stocks by scaling up from berries and vines to vineyard blocks.

Vine Signal Extraction – an Application of Remote Sensing in Precision Viticulture

This paper presents a study of precision agriculture in the wine industry. While precision viticulture mostly aims to maximise yields by delivering the right inputs to appropriate places on a farm in the correct doses and at the right time, the objective of this study was rather to assess vine biomass differences. The solution proposed in this paper uses aerial imagery as the primary source of data for vine analysis. The first objective to be achieved by the solution is to automatically identify vineyards blocks, vine rows, and individual vines within rows. This is made possible through a series of enhancements and hierarchical segmentations of the aerial images. The second objective is to determine the correlation of image data with the biophysical data (yield and pruning mass) of each vine. A multispectral aerial image is used to compute vegetation indices, which serve as indicators of biophysical measures. The results of the automatic detection are compared against a test field, to verify both vine location and vegetation index correlation with relevant vine parameters. The advantage of this technique is that it functions in environments where active cover crop growth between vines is evident and where variable vine canopy conditions are present within a vineyard block.

Seasonal Growth, Biomass Allocation, and Invasive Attributes Manifested by Dioscorea bulbifera L. (Air-Potato) Plants Generated from Bulbils in Florida

Dioscorea bulbifera is a serious invader of various ecosystems in Florida, where plants generated by its two morphotypes climb aggressively and smother supporting vegetation. There is a dearth of published research on its invasive biological attributes including vine growth and biomass production by plants generated from bulbils. Herein, we assessed these parameters in common garden studies by planting bulbils from four biomass categories (PBBCs I–IV) of both morphotypes. Vine lengths, longevity-based growth rates (VLGR), biomass, and quantities of leaves and daughter bulbils in both morphotypes showed positive correlation with the biomass of planted parental bulbils. This indicated similarity between corresponding attributes in two morphotypes. Total vine length showed strong positive correlation with VLGR, biomass, and quantities of leaves and bulbils. Overall vine longevity among plants from PBBCs I–IV did not significantly differ whereas the total vine lengths, VLGRs, number of branches, and quantities of leaves and bulbils increased with the biomass of the parental bulbils. Plants recruited by smaller bulbils allocated more biomass to leaves and tubers compared to stems and bulbils, whereas the plants recruited by larger bulbils allocated more biomass to leaves and bulbils compared to tubers and stems. Higher proportion of biomass allocation to leaves and bulbils presumably ensures immediate faster growth, longer vines, and a greater number of daughter bulbils for future recruitment of new plants. Vine length (associated with faster growth rate, capable of blanketing supporting structures and producing large quantities of bulbils) has been noted as the primary invasive biological attribute that facilitates D. bulbifera's status as a noxious exotic weed in Florida. Control measure that can reduce vine length should reduce or eliminate the invasive behavior of D. bulbifera in Florida.

Analysis of energetic performance of vine biomass residues as an alternative fuel for Chilean wine industry

The chip pruning of five different vine-producing wines was physically characterized, and its energetic value was analyzed (calorific value and ashes content principally). The material with a better energy performance was established. TCO2 emissions of this wood biomass were compared with the pine pellet, which is the most currently used solid biofuel in this industry. In both cases, the material obtaining process was studied, along with the fuel production and transport required measured in TCO2 emitted per tons.This process was done in order to replace the pellets used in the boilers of the vineyards for the chip pruning of the studied vines. The use of chips as solid biofuel inside the vineyard produces a lower TCO2 emissions than the use of pellets (0.01 and 0.484 TCO2, respectively) because less energy is needed for its production and transportation. This resulted in a decrease in the carbon footprint of the analyzed vineyard. The cost of using this chip instead of the pellets inside the vineyard was also calculated, with an annual savings in vineyard fuel requirements of US$ 23,142 from not purchasing pellets while the annual savings of using ashes instead of industrial fertilizer (CaO) is US$ 450.

Recovery of15N Labeled Fertilizer byVitis viniferaL. cv. Cabernet Sauvignon: Effects of N Fertilizer Rates and Applied Water Amounts

A study was conducted to investigate the interaction of N fertilization rates and different irrigation amounts on N fertilizer recovery efficiency (REN) of Cabernet Sauvignon in a commercial vineyard near Oakville, California. The fertilizer treatments consisted of a control (no fertilizer) and two 15N labeled ammonium nitrate fertilizer applications (6.5 and 13.0 g N/vine). The N fertilizer was applied two weeks before anthesis. The irrigation treatments were various fractions (0.25, 0.5, and 1.0) of estimated vineyard water use (ETc), with the applied water amount for the 1.0 irrigation treatment from 7 Apr to 9 Sept equivalent to 312 mm. Midday leaf water potential (Ψl) was measured throughout the season to monitor vine water status. The labeled N fertilizer was detected in the petioles and leaf blades two weeks after application. Irrigation and fertilization treatments significantly affected midday Ψl. There were significant differences in aboveground vine biomass among the treatments. In general, those supplied with more water and/or N fertilizer had greater biomass compared with nonfertilized vines under deficit irrigation. Vine uptake of the 15N labeled fertilizer increased with increasing fertilization rates and irrigation amounts. The REN was significantly different between the two 15N fertilizer treatments (29% for 6.5 g N/vine and 24% for 13.0 g N/vine). REN at harvest for the 0.25, 0.5, and 1.0 ETc irrigation treatments was ~24, 28, and 27%, respectively, although not significantly different. The data indicate that fertilizer amount had a significant effect on REN under the conditions of this study and that irrigation rates at full ETc tended to increase REN in this vineyard when compared with deficit irrigation.

Establishment of allometric models and estimation of biomass recovery of swidden cultivation fallows in mixed deciduous forests of the Bago Mountains, Myanmar

We established allometric models for fallow forests following swidden cultivation, to estimate biomass accurately in the fallows around a village in the Bago Mountains, Myanmar. By harvesting 160 individual trees from 53 species and 132 sample culms from four bamboo species, allometric equations were determined between tree/culm size variables, such as diameter at breast height (D130) and tree/culm height (H), and plant biomass components such as trunk/culm, branch, and leaf biomass in the fallows. The correlation coefficient for the allometric model for total above-ground tree biomass as a function of D1302H was high (0.956), although the value for leaf biomass was relatively low (0.626). In addition, best-fit allometric relationships for four bamboo species were established. All allometric models involving total above-ground biomass for all bamboo species had significantly high R2 values: 0.817 for G. nigrociliata, 0.877 for B. polymorpha, 0.910 for B. tulda, and 0.963 for D. strictus. A comparison between the present models and previously reported equations for above-ground biomass for tropical forests revealed that our allometric models followed the general trend for biomass estimation, with substantial differences among forest types. In addition, our results suggest that when allometric models are developed using destructive sampling methods, either all mixed species combined or select dominant species can be used, although the optimal approach would include models with all species combined to estimate biomass accumulation for mixed-species forests. Using the best-fit allometric models for trees and bamboo, we estimated tree and bamboo biomass at the community level, supplemented by understory and vine biomass. Biomass accumulation in the study area generally increased with fallow age, with a large contribution of bamboo in the fallows. To estimate biomass of secondary forests accurately, especially fallow forests, relevant allometric relationships and the intensity of swidden cultivation must be considered.

Nitrogen Status and Fermentation Dynamics for Merlot on Two Rootstocks

Adequate yeast assimilable nitrogen (YAN) levels in grape juice are necessary for yeast cells to complete fermentation to dryness. Nitrogen (N) uptake by grapevine roots varies seasonally; therefore, environmental conditions and cultural practices can affect grapevine N status. In addition, genetic differences between rootstock cultivars can influence root dynamics and, subsequently, N uptake, canopy biomass, and fruit composition. Two rootstock cultivars, 1103P and 101-14 Mgt, were fertilized with nitrogen during spring or fall or received no treatment. Vine biomass, leaf N concentration, fruit composition, juice amino-N levels, and fermentation kinetics were measured. The rootstock 1103 Paulsen (Vitis berlandieri × V. rupestris cv. 1103P) has a root system that tends to produce large canopies and high shoot growth. The rootstock 101-14 Millardet et de Grasset (V. riparia × V. rupestris cv. 101-14 Mgt) has a root system associated with smaller canopies and moderate shoot growth. The scion Merlot (V. vinifera L. cv. Merlot clone 1) was grafted onto the two rootstocks in an experimental block in Oakville, California. Merlot on 1103P had higher YAN levels and completed fermentation faster compared to Merlot on 101-14 Mgt. Differences in fermentation kinetics were observed within rootstock N treatments that were not explained by YAN levels, indicating that other factors related to N metabolism may play important roles in fermentation dynamics. Results indicated that Merlot grown on 1103P in the Napa Valley may require little to no N supplementation while Merlot on 101-14 Mgt may require N supplementation to avoid slow fermentations.

Reductions in biomass accumulation, photosynthesis in situ and net carbon balance are the costs of protecting Vitis vinifera 'Semillon' grapevines from heat stress with shade covering.

Covering whole vines with shade cloth is used to protect the vines from heat stress, but may have costs on vine productivity through reduced light availability. Our aim was to assess the carbon balance of vines growing with and without shade to quantify the impact of the covering. Whole vines were covered with 70 % shade cloth, and shoot leaf area and leaf, stem and bunch growth were followed over two growing seasons. Photosynthesis was measured in situ in all leaves along selected shoots over the growing season. A carbon balance was constructed from the difference in acquisition of carbon and the sequestration of carbon as biomass across the growing seasons. Shade covering had no initial impact on shoot growth but later reduced leaf growth and later still bunch growth. Stem growth was unaffected. Photosynthetic properties were characteristic of shade leaves, with lower rates and lower light saturation compared with well-exposed leaves. Overall, net photosynthesis was reduced by 40 % by the shade covering and was attributed to the reduced photon flux densities. From the carbon balance, vines were reliant on carbon reserves over 6 weeks after budbreak until current photosynthate increased sufficiently to supply the growth. Shade covering impacted most on biomass accumulation to leaves and bunches at the stage when the vines became autotrophic, consistent with the reduction in carbon acquisition. The markedly high carbon demand by bunches caused a mid-season negative carbon balance, implying that shoots had to draw further on reserves to supply the carbon. Shade covering over whole grapevines exacerbated the imbalance between the supply of and demand for carbon and greatly reduced vine biomass, especially reproductive allocation. Covering vines with shade cloth to protect the vines from heat events, therefore, had major costs in the carbon economy.