Search Results
A study was conducted to determine the effects of crop removal on gas exchange parameters of `Thompson Seedless' grapevines grown in the San Joaquin Valley of California. Vines were either irrigated at full ET or not irrigated throughout the growing season. Clusters were removed subsequent to veraison, when the fruit soluble solids were ≈15° Brix. Reductions in leaf net CO2 assimilation rate (A) were measured within 1 day of fruit removal for both irrigation treatments and remained such until the end of the experiment. The greatest reduction in A due to crop removal on a diurnal basis was with the non-irrigated vines between 0800 and 1000 hr. The reduction in A subsequent to crop removal was not the result of an accumulation of either starch or sugars in leaf tissue. The greater reduction in A of non-irrigated vines after fruit removal may have been due to the lack of strong, alternate sinks as vegetative growth was minimal due to water stress during the experimental period.
A weighing lysimeter (with a soil container 2 m wide, 4 m long and 2 m deep) was installed at the University of California's Kearney Ag Center in 1987. Diurnal, daily and seasonal vine water use has been measured yearly since then. Vine water use was 350, 400 and 580 mm the first, second and third years after planting. respectively. Vine water use (from budbreak to October 31) the subsequent four years averaged 815 mm per year. Reference crop ET (ETo) averaged 1172 mm (from budbreak to October 31) over the course of the study. Diurnal vine water use was highly correlated with the diurnal course of solar radiation. Maximum ET averaged 50 L vine-1 day-1 during the middle part of the growing season. Experimental vines surrounding the lysimeter were irrigated at various fractions (from 0 to 140% in increments of 20%) of vine water was measured with the weighing lysimeter. Maximum yields were obtained with the 80% irrigation treatment This study demonstrated the deleterious effects of both over and under irrigation on yield of grapevines.
Entire Thompson Seedless grapevines (to include the root system) were harvested at regular intervals over a two year period. Dry matter, soluble carbohydrates, N and K were quantified on an individual organ basis for each date. The pattern of dry matter partitioning to the roots and trunk were similar from one year to the next. Decreases in dry weight in the roots and trunk were accompained by decreases in soluble carbohydrates. The concentration of K in the roots remained almost constant over the two year period while that of N fluctuated from less than 1% (dry wt basis) to more than 2.5% depending on the time of the year. The dynamics of N and K within the trunk on a concentration or content (g vine-1) basis were similar to one another. N and K were remobilized from the trunk early in the growing while only N was remobilized from the root system. Remobilization of N from the roots took place from berry set until harvest.
Abstract
Data were collected over 3 years to provide detailed information on growth and development of ‘Thompson Seedless’ grapevines used for raisin production. Leaf area and leaf, shoot, and cluster dry weights were measured throughout the growing season. Results were plotted against growing degree days (GDDs), using a minimum temperature threshold of 10°C, after budbreak. There was a linear increase in leaf area and vegetative dry matter from about 200 to 1000 GDDs after budbreak. Cluster dry weight increased linearly from 750 GDDs after budbreak until harvest. While shoot numbers per vine increased 70% from 1983 to 1985, there was not a similiar increase in the amount of dry matter per vine. Weight per unit leaf area (WL) increased from ≈ 40 g·m-2 early in the season to >65 g·m-2 90 days after fruit harvest. Results indicate that vines in this vineyard maintained a constant growth pattern year after year when growth was plotted vs. growing degree days.
Abstract
Nitrogen content and concentration were determined on field-grown ‘Thompson Seedless’ grapevines in the San Joaquin Valley of California. Individual vine replicates were harvested throughout the growing season over a 3-year period. There was a linear increase in vine N content from budbreak to 1000 growing degree days (GDDs) later. During this time, the accumulation of N was primarily in the stems and leaves. Subsequent to 1000 GDDs, the increase in vine N was due to the accumulation of N in the clusters. Throughout the season, N concentration in all vine parts decreased. The increase in cluster N content did not appear to occur at the expense of N remobilization from the vegetative structures measured in this study. On a single date, the N concentration of leaves varied throughout the canopy—the outer layer of leaves contained 3.2% N, while leaves in the interior of vine contained 2.4% N. The loss of N from the vine through leaf fall and cane pruning was about 20 and 15 g, respectively. The data were similiar from year to year with regards to both N concentration and content in leaves, stems, and clusters when plotted vs. GDDs. The approximate requirement of N for current season’s growth of ‘Thompson Seedless’ grapevines used for raisin production was 75 g/vine, or 84 kg·ha-1.
An ongoing study measuring grapevine (Vitis vinifera L., cv. Thompson Seedless) water use with a weighing lysimeter is being used to develop a model to simulate vine water use on both a diurnal and seasonal basis. A method to calculate the aerodynamic resistance (ra) of the vines was first determined. Subsequently, a model to predict canopy resistance (rc based solely upon intercepted photon flux density (PFD) was developed. The modeled values of ra and rcwere substituted into a resistance-energy balance equation to predict vine ET. The modeled parameters were validated against diurnal measurements of ET from the lysimeter. The greatest difference between modeled and measured rc occurred prior to 1000 h and subsequent to 1500 h each day. The model overestimated vine ET by 14 and 23% on 16 and 24 June, 1992, respectively. Ambient temperature and vapor pressure deficit were greater on 24 June than on 16 June. Refinements in calculating PFD interception by the vine's canopy early and late in the day and incorporating the effects of other environmental factors on grape stomatal conductance should improve the predictive capabilities of the model.
Leaf area development and canopy structure are important characteristics affecting yield and fruit quality of grapevines. Trellising systems and wide row spacing are common viticultural practices that violate key assumptions of currently available indirect methods of leaf area determination. We have developed a protocol for using a commercially available instrument to determine leaf area index (LAI) indirectly in a trellised vineyard. From knowledge of plant spacing, leaf area per vine can be calculated as required. A derived calibration equation resulted in a near 1:1 relationship (y = 0.00 + 1.00 X; r2 = 0.998) between actual and indirectly determined LAI over a range of LAI induced by irrigation treatments. The protocol involved covering 75% of the sensor with a manufacturer-supplied field of view delimiter and masking data from the outer three (of five) concentric radiation sensors. The protocol could form the basis for a general measurement technique, but may require local calibration.
Abstract
Cytokinins applied to axillary buds of apple shoots overcame apical dominance. Axillary buds on actively growing apple shoots produced spurs and lateral branches when treated with cytokinins. Buds on shoots that had not received sufficient chilling to break rest were also induced to grow with cytokinins.
A study was conducted to compare three measurements of determining water status of grapevines (Vitis vinifera L.) in the field. Predawn leaf water potential (ΨPD), midday leaf water potential (Ψl), and midday stem water potential (Ψstem) were measured on `Chardonnay' and `Cabernet Sauvignon' grapevines grown in Napa Valley, California late in the 1999 growing season. Both cultivars had been irrigated weekly at various fractions (0, 0.5, and 1.0 for `Chardonnay' and 0, 0.5, 0.75, and 1.5 for `Cabernet') of estimated vineyard evapotranspiration (ETc) from approximately anthesis up to the dates of measurements. Predawn water potential measurements were taken beginning at 0330 hr and completed before sunrise. Midday Ψl and Ψstem measurements were taken only between 1230 and 1330 hr. In addition, net CO2 assimilation rates (A) and stomatal conductance to water vapor (gs) were also measured at midday. Soil water content (SWC) was measured in the `Chardonnay' vineyard using a neutron probe. Values obtained for ΨPD, Ψl, and Ψstem in this study ranged from about -0.05 to -0.8, -0.7 to -1.8, and -0.5 to -1.6 MPa, respectively. All three measurements of vine water status were highly correlated with one another. Linear regression analysis of Ψl and Ψstem versus ΨPD resulted in r 2 values of 0.88 and 0.85, respectively. A similar analysis of Ψl as a function of Ψstem resulted in an r2 of 0.92. In the `Chardonnay' vineyard, all three methods of estimating vine water status were significantly (P < 0.01) correlated with SWC and applied amounts of water. Lastly, ΨPD, Ψl, and Ψstem were all linearly correlated with measurements of A and gs at midday. Under the conditions of this study, ΨPD, Ψl, and Ψstem represent equally viable methods of assessing the water status of these grapevines. They were all correlated similarly with the amount of water in the soil profile and leaf gas exchange as well as with one another.
Abstract
The relationship between net CO2 assimilation rate (A) and nitrogen (N) content during leaf senescence was determined on field grown Vitis vinifera L. ‘Thompson Seedless’ leaves. Measurements commenced subsequent to fruit harvest and were made at weekly intervals until leaf fall. Maximum A was greater than 2.0 nmoles CO2 cm-2s-1 when leaf N content was greater than 3.0%. There was a linear relationship between A and percent N content regardless of whether A was expressed on an area or dry weight basis. However, the correlation between A on a dry weight basis and percent leaf N was greater than that between A on an area basis and percent leaf N. The percent N content and net CO2 assimilation rate decreased as weight per unit leaf area (W) increased. There was no effect on leaf N content on stomatal conductance (gs) when N content was greater than 2%. The results suggest that leaf N content could be used an as indicator of a grapevine's leaf photosynthetic capacity subsequent to fruit harvest.