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- Author or Editor: Thomas H. Whitlow x
Abstract
Only a few species are capable of colonizing extreme environments, whereas more moderate environments can support many more. The diversity of species in a habitat is thus controlled by the environment, whether by soil fertility, altitude or any other factor. This diversity reflects the number of species adapted to grow in a habitat, and the nature of this adaptation must be examined in light of the physiological effect of the environmental factors making up the habitat, and their variation in time and space (11).
Changes in photosynthesis and root morphology during flooding were studied in container-grown 2- to 3-year-old Acer rubrum L. saplings. The seed was collected from opposite ends of a hydrologic gradient: two upland xeric sites [the George Washington National Forest in Page County, Va. (38°25'N, 78°35'W), and the Robinson Forest in Perry County, Ky. (37 °9'N, 83°7'W)] and a floodplain hydric site [the Presquile National Wildlife Refuge along the James River in Chesterfield County, Va. (37°21'N, 77°16'W)]. Each xeric site, containing various half-sib families (maternal parent known, paternal parent from one or more sources), was compared to a different hydric site half-sib family. After 1 week of flooding, the xeric-site trees had lower net photosynthesis than the hydric-site trees and remained significantly lower for the duration of the study. After an initial drop, hydric-site plants showed a recovery in net photosynthesis, indicating a greater ability to acclimate to a flooding stress. Seventy-one percent of the hydric-site plants developed adventitious roots and all retained their leaves. Xeric-site plants did-not develop adventitious roots and 61% were defoliated after 60 days of continuous flooding. The results indicate ecotypic differentiation in physiological response between Acer rubrum populations collected from opposite ends of a hydrologic gradient.
Growth and physiological characteristics were evaluated in autografted and reciprocally grafted plants of Prunus avium L. ×pseudocerasus Lindl. `Colt' and Prunus cerasus L. `Meteor'. Containerized plants were grown for 150 days in a greenhouse under either well-watered or water-stressed conditions. Both the scion and rootstock influenced growth (relative growth rate, R̄), morphological [leaf area : root surface area (LARSA) and specific leaf area (SLA)], and physiological (mean net assimilation rate, Ē) characteristics of grafted plants. Regardless of the watering regime, plants with `Meteor' scions and `Colt' rootstocks maintained higher R̄ than plants with `Colt' scions and `Meteor' rootstocks. This enhanced growth occurred as a result of higher Ē. Measurements on water-stressed plants also showed that the graft combination of `Meteor' on `Colt' had the lowest LARSA, while the reciprocal combination of `Colt' on `Meteor' had the highest. Differences in LARSA among water-stressed plants primarily reflected changes in SLA, as influenced by both rootstock and scion, and not in partitioning of dry weight between these organs.
Tissue osmotic potential(Ψπ) and solute constituents were evaluated in leaves and roots of well-watered and water-stressed Prunus avium L. × pseudocerasus Lindl. `Colt' and Prunus cerasus L. `Meteor'. Osmotic potential at full turgorΨπ,sat decreased in response to water stress for leaves and roots of both cultivars. For `Colt', a cultivar with an indeterminate growth habit,Ψπ,sat decreased by 0.56 MPa and 0.38 MPa for terminal expanding leaves and older expanded leaves, respectively. For `Meteor', a cultivar with a determinate growth habit,Ψπ,sat decreased by ≈0.47 MPa in both terminal and older leaves. RootΨπ,sat was alike for both cultivars and showed a similar decrease of 0.20 MPa in response to water stress. Roots had considerably higherΨπ,sat than did leaves in both cultivars, irrespective of irrigation treatment. Soluble carbohydrates and potassium (K+) were the major solute constituents in both cultivars. Of the soluble carbohydrates, sorbitol was found in the greatest concentration and accounted for the bulk of water stress-induced solute accumulation in both cultivars. Regardless of the irrigation treatment, mature leaves of `Meteor' consistently had lowerΨπ,sat (typically 0.4 MPa) than `Colt'. This variation in Ψπ,sat between Prunus cultivars suggests the potential for selection of cultivars with low Ψπ,sat and possibly superior drought resistance.
Beach plum is a shrub native to Atlantic coastal sand dunes from Maine to Maryland, where it is subject to drought and low nutrient and water holding soil. Since colonial times beach plum fruit has been collected from the wild for the production of preserves, an activity that endures today as a cultural tradition and cottage industry. Currently, the supply of fruit from wild stands does not meet the market's demand; hence, beach plum could be a new crop for many growers in the Northeastern U.S. For the past 4 years, a partnership of growers, Univ. of Massachusetts Extension, and Cornell Univ. has experimented with standard orchard cultural methods for beach plum production in coastal Massachusetts. During Aug. 1999, we harvested the first crop from our experimental orchard. The factorial experiment evaluates the effects of irrigation, mulch, and fertilizer on growth and yield of beach plum. Basal and axial growth were strongly correlated and were greater in fertilized than unfertilized treatments. Within fertilizer regime irrigation and mulch had less effect on growth than fertilizer. Fruit yield (dry weight and fresh weight) was greater in fertilized plots. Irrigation had no positive influence on yield. Average fruit diameter and °Brix were greater in the fertilized and unirrigated treatments.
Four each of landscape-sized Fraxinus Pennsylvania Marsh. (green ash), Quercus coccinea Muenchh. (scarlet oak), Corylus colurna L. (Turkish hazelnut) and Syringa reticulata Hara `Ivory Silk' (tree lilac) were established on a rhizotron in Ithaca, New York, and root and shoot growth characteristics were observed throughout 1992. Root growth did not begin on any species before bud break. Green ash, scarlet oak and Turkish hazelnut exhibited recurrent shoot growth. Most root growth occurred during periods of bud rest, although no marked antagonism between shoot and root growth was evident. Green ash root growth was synchronous with shoot growth. The root harvest zone of green ash and tree lilac contained higher root length densities, and roots contained within appeared less suberized than that of Turkish hazelnut or scarlet oak. Root spread: crown spread ratio was greatest for Turkish hazelnut. Little root growth occurred on any species after fall leaf drop or when soil temperatures were below 5C. Implications for transplanting are discussed.
Root and shoot phenology were observed, and root length within rootballs were calculated for Fraxinus pennsylvanica Marsh. (green ash), Quecus coccinea Muenchh. (scarlet oak), Corylus colurna L. (Turkish hazelnut), and Syringa reticulata (Blume) Hara `Ivory Silk' (tree lilac) trees established in a rhizotron. Easy-to-transplant species (green ash and tree lilac) had more root length within rootballs than difficult-to-transplant species (Turkish hazelnut and scarlet oak). Shoot growth began before root growth on all species except scarlet oak, which began root and shoot growth simultaneously. Fall root growth ceased for all species just after leaf drop. Implications for tree transplanting are discussed.
Lead contamination of surface soils is a frequently encountered problem of environmental concern, and Pb toxicity in humans is considered the most immediate environmental risk associated with Pb-contaminated soils. Phytoextraction, using plants to remove pollution from soil, is the subject of recent phytoremediation research. Major limitations of lead phytoextraction are low Pb availability in soil and poor Pb translocation from roots to shoots. These limitations indicate that the accumulation of Pb in shoots can be feasible only through the application of synthetic chelation agents, such as EDTA, which facilitate metal dissolution, uptake, and transport. Induced phytoextraction of Pb from contaminated soils has been demonstrated with Brassica juncea (Indian mustard), but B. juncea is not ideal for phytoextraction because of its low biomass. Inducing Pb accumulation in low-input, high-biomass perennial plants is a more practical and manageable strategy for phytoextraction. Tree and turf species have not been explored as a plant community to remove Pb from contaminated soils. The objective of this study is to induce Pb absorption from contaminated soil with low-input perennial plants, Festuca arundinacea (tall fescue) and Acer rubrum (red maple), through proper timing and application of synthetic chelation agents. This study is expected to benefit the community of scientists and environmental researchers concerned with the development of ecologically sound and economically desirable technologies for the remediation and restoration of contaminated soils. This poster presentation provides a condensed visual interpretation of the Pb phytoextraction, background information, and an update on progress of the study. E-mail rsbl2@cornell.edu
The objectives of this study were to determine root and shoot growth periodicity for established Fraxinus pennsylvanica Marsh. (green ash), Quercus coccinea Muenchh. (scarlet oak), Corylus colurna L. (Turkish hazelnut), and Syringa reticulata (Blume) Hara `Ivory Silk' (tree lilac) trees and to evaluate three methods of root growth periodicity measurement. Two methods were evaluated using a rhizotron. One method measured the extension rate (RE) ofindividual roots, and the second method measured change in root length (RL) against an observation grid. A third method, using periodic counts of new roots present on minirhizotrons (MR), was also evaluated. RE showed the least variability among individual trees. Shoot growth began before or simultaneously with the beginning of root growth for all species with all root growth measurement methods. All species had concurrent shoot and root growth, and no distinct alternating growth patterns were evident when root growth was measured by RE. Alternating root and shoot growth was evident, however, when root growth was measured by RL and MR. RE measured extension rate of larger diameter lateral roots, RL measured increase in root length of all diameter lateral roots and MR measured new root count of all sizes of lateral and vertical roots. Root growth periodicity patterns differed with the measurement method and the types of roots measured.
Floricane-fruiting (summer-bearing) raspberries (Rubus idaeus L.) were grown outdoors in pots in upstate New York until mid-December when the chilling requirement was fulfilled. They were moved into a greenhouse and placed at a density that is three times higher than field planting. Bumble bees (Bombus impatiens Cresson) were introduced at flowering for pollination. Fruiting occurred from mid-February through mid-April, a time when the retail price for raspberries is between $3.00 and $6.00 for a half pint (180 g). Fruit quality was high, and individual 2-year-old plants averaged 11 half pints (2 kg) of marketable fruit. These yields and retail prices are equivalent to 19,000 lb and $142,000 per acre (21 t, $350,000 per ha). Raspberry production during winter allows growers to dramatically extend the harvest season and to produce a high-value crop at a time when greenhouses often are empty.