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  • Author or Editor: Bruce R. Roberts x
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Abstract

Potted seedlings of white birch (Betula papyrifera Marsh.) and pin oak (Quercus palustris Muenchh.) were grown in the field for 3 months in relatively high- and low-ambient sulfur dioxide air. Biweekly throughout the growing season, plants from each site were harvested, and height and leaf, stem, and root dry weight were measured. The overall growth of white birch, an SO2-sensitive species, was found to be greater in the higher, but sub-phytotoxic SO2 environment. Conversely, the growth of pin oak, an SO2-tolerant species, was greater at the low SO2 site.

Open Access

Abstract

Intraclonal variation in Ulmus americana, American elm and U. pumila, Siberian elm was compared with seedling variation in the same species for the following characteristics: height growth; shoot, root, and total fresh weight; stem, leaf, root and total dry weight; root-shoot ratio, and leaf area. Intraclonal variation was as great as seedling variation for all characteristics in 3-month-old American and 12-month-old Siberian elms and for height growth in 13-month-old American elms. It was significantly less for all other characteristics in the 13-month-old American elm clone.

Open Access

Abstract

The capacity of rhododendron (Rhododendron catawbiense Michx., cv. Nova Zembla) and firethorn (Pyracantha coccinea M. J. Roem. var. Lalandii (Duren) Dipp.) to change ambient SO2 levels in a closed fumigation system was studied. P. coccinea removed greater quantities of SO2 at faster rates than R. catawbiense. Differences in leaf surface characteristics between the 2 species suggest that at least part of the SO2 uptake mechanism may involve a surface-mediated response to the pollutant.

Open Access

Two-year-old seedlings of red maple (Acer rubrum L.) were fumigated with SO2 (0.0, 0.5, 2.0, and 4.0 ppm) 8 hours daily for two 3-day periods spaced 3 days apart. Response to acute SO2 stress was determined by measuring changes in ethylene biosynthesis and membrane permeability. Ethylene evolution was a useful indicator of the onset of SO2 stress in red maple, but was not a particularly good indicator of the degree of stress. Membrane permeability was not as sensitive to the initial stages of SO2 stress, and significant changes in permeability were noted only at higher concentrations of this pollutant (> 2.0 ppm).

Free access

Self-incompatibility (SI) is the inability of otherwise fertile gametes to produce viable zygotes upon self-fertilization. The S locus of chromosome 1 in Lycopersicon is thought to be the main controlling factor in SI. However, the significance of other chromosome segments in the control of SI or the effect of a foreign genetic background on the S locus has not been thoroughly explored. In addition, the relationship between SI and wider interspecific crossing barriers remains unclear. Using DNA and protein markers for chromosome 1, we have created a series of backcross lines that contain either 1) the SI locus and flanking chromosome region from a SI species in a SC species background or 2) the same chromosome region from a SC species in a SI species background. The reproductive behavior of these plants will be discussed.

Free access

Two biosolid-containing waste media [sewage sludge compost and incinerated biosolids (flume sand)] were tested individually, together, and in combination with a commercial growing medium for growing wildflower sod in greenhouse trials over a 3-year period. A medium composed of flume sand and Metromix (7:3 weight/weight) in 7.5 {XtimesX} 10.5 {XtimesX} 2-inch deep (19 {XtimesX} 27 {XtimesX} 5-cm) plastic trays seeded at 20 oz/1000ft2 (6.1 g·m-2) with cosmos (Cosmos bipinnatus), cornflower (Centaurea cyannis), plains coreopsis (Coreopsis tinctoria), white yarrow (Achillea millefolium) and purple coneflower (Echinacea purpurea) produced a suitable wildflower sod in 10 to 12 weeks. A single application of slow release fertilizer (Osmocote 14-14-14, 14N-4.2P-11.6K) applied as a top dressing had no significant effect on sod development; however, a 4-mil [0.004-inch (0.10-mm)] polyethylene barrier placed in the base of each container resulted in increased dry weight accumulation and a higher root to shoot ratio relative to sod grown without plastic.

Full access

Two biosolid-containing waste media [composted sewage sludge (Com-Til) and incinerated biosolids (flume sand)] were evaluated as soilless media for growing `Crenshaw', `Penncross', and `ProCup' creeping bentgrass sod (Agrostis palustris). The media were combined with sand and either sphagnum peat or a commercial growing mix (Metromix) and leached with 5.1 fl oz (150 mL) tap water either zero, one or three times before seeding. Leaching with tap water to remove soluble salts had no beneficial effect on germination or dry mass accumulation. Flume sand was not a particularly good rootzone component for growing creeping bentgrass sod; however, a sieved [0.08-inch (2-mm)] medium consisting of sand, Com-Til and Metromix (8:1:1, by weight) seeded with `ProCup' creeping bentgrass at 2 lb/1000 ft2 (9.8 g·m-2) and grown over 4-mil (0.004-inch, 0.10-mm) plastic in 3.5 × 7.5 × 2-inch deep (9 × 19 × 5-cm) trays produced good sod in about 6 weeks.

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In the United States, urban population growth, improved living standards, limited development of new water supplies, and dwindling current water supplies are causing the demand for treated municipal water to exceed the supply. Although water used to irrigate the residential urban landscape will vary according to factors such as landscape type, management practices, and region, landscape irrigation can vary from 40% to 70% of household use of water. So, the efficient use of irrigation water in urban landscapes must be the primary focus of water conservation. In addition, plants in a typical residential landscape often are given more water than is required to maintain ecosystem services such as carbon regulation, climate control, and preservation of aesthetic appearance. This implies that improvements in the efficiency of landscape irrigation will yield significant water savings. Urban areas across the United States face different water supply and demand issues and a range of factors will affect how water is used in the urban landscape. The purpose of this review is to summarize how irrigation and water application technologies; landscape design and management strategies; the relationship among people, plants, and the urban landscape; the reuse of water resources; economic and noneconomic incentives; and policy and ordinances impact the efficient use of water in the urban landscape.

Free access