No abstract

Aim: The nutrient reserves in the grapevine perennial structure perform a critical role in supplying the grapevine with nutrients when demand cannot be sustained by root uptake. The seasonal changes in these reserves largely depend on the developmental stage and the associated growth requirements. These stored reserves are, in turn, influenced by environmental conditions and vineyard management practices, such as production levels and water availability. The aim of this study was to assess the nutrient dynamics of a major wine grape variety grown in Australia to determine the key nutrient uptake periods and to understand the mobilization patterns throughout a season.Methods and results: The own-rooted 10-year-old Shiraz vines used for the trial were located in the Riverina, which is a hot inland grape-growing region in New South Wales, Australia. Uniformly sized vines, identified by trunk circumference, were selected for 11 excavation dates with four replicates, from a month before bud-burst to leaf-fall. The above-ground section of the vines were separated into the different perennial, vegetative and reproductive organs. The below-ground section of the vines were obtained in an allocated area (6 m2/vine) and were excavated to a depth of 1 m, and the roots were separated into rootstock and three root sizes. Sub-samples of each tissue were freeze-dried and the remaining tissues were oven-dried at 70°C, and for both procedures the dry weight (DW) was recorded. For the nutrient analysis, the tissue sub-samples were ground up, and nutrients were determined with an nitrogen analyzer and an ICP-OES.The annual organs showed the highest nitrogen (N) concentrations in spring, with the leaves having 3% and inflorescences 2.5%, but stem N concentration was highest at the end of the season with 0.7% DW. Root N concentrations are at least double the other perennial sections, with these reserves declining early in the season and being replenished by leaf-fall. The changes in concentrations for perennial sections are similar for the other macro nutrients, but differ for Ca and S in the annual tissues. The N content of the perennial structure declined considerably until flowering, with a sharp increase after harvest. The majority of the N uptake occurred four weeks before flowering and four weeks before veraison, and more than half the N of the vine was allocated to the annual organs at harvest. Other macro nutrients show a pattern of decline and replenishment in the roots and wood and most nutrients were taken up predominantly four weeks prior to flowering.Conclusions: An important finding from the study revealed that the amount of each nutrient allocated to the perennial structure and annual parts varied between the nutrients. This understanding of the nutrient dynamics will lead to an optimization of individual nutrient status and supply for grapevines.Significance and impact of the study: This is the first time that whole-vine nutrient levels were followed through the season under Australian conditions and on a wine grape variety for all macro nutrients. Such information is critical to allow precise prediction and modeling of grapevine nutrient requirements.

To gain a better understanding of environmental effects on grapevines and the physiological regulation of acclimation, we determined the effects of soil temperature (14 or 24°C) between anthesis and veraison on growth, nonstructural carbohydrates, cytokinins, abscisic acid, and leaf function of potted Vitis vinifera cv. Shiraz. Plants of each regime were selected from two groups that had been grown in a glasshouse from three weeks prior to budbreak at an average soil temperature of either 13 or 23°C. Soil temperature between anthesis and veraison affected utilization and restoration of root and trunk nonstructural carbohydrates and changes in biomass of major plant organs. Soil warming promoted shoot growth via utilization of starch reserves, while soil cooling promoted starch storage in both the root and wood and shifted overall biomass partitioning to the roots. A change in soil temperature from warm to cool through flowering was also associated with reduced fruit set. Diurnal courses of photosynthesis, transpiration, and stomatal conductance after fruit set were significantly affected by soil temperature. Phytohormones (cytokinin and abscisic acid) were measured in the xylem sap and leaves at fruit set and veraison. Differences between these two sample types during grapevine development highlight a phytohormone shift likely involved in postveraison fruit ripening. We conclude that soil temperature significantly affects grapevine growth and that the responses are mediated largely by an influence of temperature on mobilization of nonstructural carbohydrates from the roots.

Variability in fruit quality greatly impedes the profitability of an orchard. Modelling can help find the causes of quality variability. However, studies suggest that the common assimilate pool model is inadequate in terms of describing variability in organ biomass. The aim of the current study was to compare the performances of the common assimilate pool and phloem carbohydrate transport models in simulating phloem carbohydrate concentration and organ biomass variability within the whole-plant functional-structural grapevine (Vitis vinifera L.) model that we developed previously. A statistical approach was developed for calibrating the model with a detailed potted experiment that entails three levels of leaf area per vine during the fruit ripening period. Global sensitivity analysis illustrated that carbohydrate allocation changed with the amount of leaf area as well as the limiting factors for organ biomass development. Under a homogenous canopy architecture where all grape bunches were equally close to the carbohydrate sources, the common assimilate pool and phloem transport models produced very similar results. However, under a heterogeneous canopy architecture with variable distance between bunches and carbohydrate sources, the coefficient of variation for fruit biomass rose from 0.01 to 0.17 as crop load increased. These results indicate that carbohydrate allocation to fruits is affected by both the size of crop load and fruit distribution, which is not adequately described by the common assimilate pool model. The new grapevine model can also simulate dynamic canopy growth and be adapted to help optimise canopy architecture and quality variability of other perennial fruit crops.