Search Results (5)

The profitability of modern apple orchard plantings depends largely on how rapidly the costs of planting are returned. Tree establishment and growth in the formative years are often can be limited by transplant shock associated with bare-root trees. In this experiment, we examined the effect of two planting systems, air-pruning containers, and field-grown liners, on above- and below-ground growth and development during the first year in the nursery. M9 ‘Nic 29’ bench grafts for three apple cultivars of different vigor classes, ‘Fuji’ (high vigor), ‘Gala’ (moderate vigor), and ‘Honeycrisp’ (low vigor). We hypothesized that air root-pruning containers would alter rooting distribution compared to field-grown liners by increasing fine root production, and this, in turn, would result in improved resource allocation and greater biomass partitioned to above-ground organs. Bench grafts were divided evenly between a field-grown liner bed (for bare root production) and an air-pruning container system. Air-pruning containers produced trees with significantly more root tips and greater total root length per tree than field-grown liners. Importantly, air-pruning containers resulted in a marked and significant increase in roots < 0.4 mm in diameter; however, field-grown liners produced trees had significantly more roots with diameters > 1.5 mm and, thus, significantly greater root dry matter content (DMC). Above-ground parameters (scion length, DMC of wood and leaves, and individual leaf area and DMC) were significantly increased for plants in air-pruning containers. Generally, the growth benefits from air-pruning containers were less pronounced in ‘Gala’ compared to ‘Honeycrisp’ or ‘Fuji’. The percentage of total DMC partitioned to the canopies of air-pruning containerized trees was significantly greater than field-grown liners. Full article

Studies on plant growth and trait variation along environmental gradients can provide important information for identifying drivers of plant invasions and for deriving management strategies. We used seeds of the annual plant invader Ambrosia artemisiifolia L. (common ragweed) collected from an agricultural site in Northern Italy (226 m. a.s.l; Mean Annual Air Temperature: 12.9 °C; precipitations: 930 mm) to determine variation in growth trajectories and plant traits when grown along a 1000-m altitudinal gradient in Northern Italy, and under different temperature conditions in the growth chamber (from 14/18 °C to 26/30 °C, night/day), using a non-liner modeling approach. Under field conditions, traits related to plant height (maximum height, stem height, number of internodes) followed a three-parameter logistic curve. In contrast, leaf traits (lateral spread, number of leaves, leaf length and width) followed non-monotonic double-Richards curves that captured the decline patterns evident in the data. Plants grew faster, reaching a higher maximum plant height, and produced more biomass when grown at intermediate elevations. Under laboratory conditions, plants exhibited the same general growth trajectory of field conditions. However, leaf width did not show the recession after the maximum value shown by plants grown in the field, although the growth trajectories of some individuals, particularly those grown at 18 °C, showed a decline at late times. In addition, the plants grown at lower temperatures exhibited the highest value of biomass and preserved reproductive performances (e.g., amount of male inflorescence, pollen weight). From our findings, common ragweed exhibits a high phenotypic plasticity of vegetative and reproductive traits in response to different altitudes and temperature conditions. Under climate warming, this plasticity may facilitate the shift of the species towards higher elevation, but also the in situ resistance and (pre)adaptation of populations currently abundant at low elevations in the invasive European range. Such results may be also relevant for projecting the species management such as the impact by possible biocontrol agents. Full article

Field production of seedlings used to create nursery stock liners involves transplanting and root pruning that can alter root system architecture. Seedlings of eight species of trees commonly used in urban landscapes were selected based on the configuration of their woody lateral roots; Preferred (maximum gap between roots ≤90 degrees), Acceptable (maximum gap 120–150 degrees), and Inferior (≥180 degree gap—no lateral roots on one side). The lateral root configuration (LRC) of the seedlings was compared to the LRC one year after replanting. The number of lateral or regenerated roots alone was generally adequate to form an acceptable root flare (≥3 roots) one year after seedlings were replanted. The maximum gap in lateral roots as a seedling was not consistent with the maximum gap one year after the seedlings were replanted in most species. It often became larger. Neither lateral roots nor regenerated roots alone could reliably produce a root structure with an acceptable maximum gap between roots. Lateral roots and roots regenerated from the pruned end of the main root, together produced enough flare roots one year after replanting with a small enough maximum gap in the radial distribution for good stability. This information may be an initial step in developing criteria for seedling grading systems that will improve root systems of nursery stock grown for planting in urban landscapes. Full article

For urban trees with strong taproots, a shift in root growth towards increased lateral root development could improve tree performance in compacted, poorly drained urban soils. In effort to achieve this desired shift, various propagation and production practices exist within the nursery industry. However, the effectiveness of practices used to disrupt taproot development, as well as their impact on root architecture, has been largely undocumented. To determine how seedling root systems respond to taproot growth disruption, we pruned oak seedling taproots either mechanically at 5 and/or 15 cm, or via air pruning at 15 cm. Taproot regeneration and lateral root development were evaluated after two years. Taproot pruning resulted in multiple regenerated taproots. The location and number of times the taproot(s) was pruned did not appear to alter the ultimate number. Mechanical taproot pruning did not affect lateral root development above the first pruning cut location at 5 or 15 cm, but generally increased the density of lateral roots below the pruning cut, likely due to the multiple taproots present. Most lateral roots were fine roots less than 1 mm in diameter (fine roots), being unlikely to become long-lived components of the root system architecture. The average number of lateral roots on air pruned (AP) seedlings was generally greater than on the same taproot segment of control (C) seedlings. To determine how these seedling changes impact the root regeneration of liner stock, we planted both taproot pruned and taproot air pruned seedlings in in-ground fabric bags filled with field soil (B) or directly into the field without bags (F). Root regeneration potential (RRP) at the bottom and lateral surfaces of the root ball were evaluated. There was less RRP on the lateral surface of the root ball in taproot air pruned, container-grown (CG) compared to taproot pruned, bare root (BR) bur oak liners, and there was no difference in red oak liners. The multiple taproots of mechanically pruned BR seedlings did not result in excessive taproot development as liners. In contrast, CG seedling taproots restricted by air pruning produced more regenerated taproots after transplanting. While seedling taproot growth disruption does disrupt the growth of a dominant single taproot and alters the architecture toward increasing the number of lateral roots, these practices do not result in laterally dominated root architecture at the liner stage of nursery production. Future research should determine how these production methods effect lateral root growth after a tree is established in the landscape and determine appropriate combinations of production methods for different species. Full article

‘BRS Isis’ is a new hybrid seedless table grape tolerant to downy mildew with a good adaptation to the tropical and subtropical climates. Gray mold, caused by Botrytis cinerea Pers. ex Fr. is known as the most important postharvest mold in table grapes, causing extensive losses worldwide. As the postharvest behavior of ‘BRS Isis’ is still unknown, the objective of this work was to evaluate the postharvest preservation and B. cinerea mold control of this new grape cultivar, grown under the double-cropping a year system. Grape bunches were purchased from a field of ‘BRS Isis’ seedless table grapes trained on overhead trellises located at Marialva, state of Parana (South Brazil). Grapes were subjected to the following treatments in a cold room at 1 ± 1 °C: (i) Control; (ii) SO₂-generating pad; (iii) control with bunches inoculated with the pathogen suspension; (iv) SO₂-generating pad with bunches inoculated with the pathogen suspension. The completely randomized experimental design was used with four treatments, each including five replicates. The incidence of gray mold and other physicochemical variables, including bunch mass loss, shattered berries, skin color index, soluble solids (SS), titratable acidity (TA), and SS/TA ratio of grapes, were evaluated at 50 days after the beginning of cold storage and at seven days at room temperature (22 ± 2 °C). The ‘BRS Isis’ seedless grape, packaged with SO₂-generating pads and plastic liners, has a high potential to be preserved for long periods under cold storage, at least for 50 days, keeping very low natural incidence of gray mold, mass loss, and shattered berries. Full article