Search Results

You are looking at 1 - 9 of 9 items for

  • Author or Editor: Bert T. Swanson x
Clear All Modify Search

To increase root fibrosity, acorns of northern red oak (Quercus rubra L.) were germinated and subjected to several radicle clipping (+/-) and K-IBA concentration treatments combintations prior to planting. Taproots and laterals ≥ 1 mm in diameter at the point of origin were counted. Low concentrations of K-IBA (0-4000 ppm) resulted in four root morphologies: 1) a single taproot and 3-6 laterals (no clipping/no K-IBA), 2) 4-5 taproots and 1-3 laterals (clipped only), 3) a single taproot and 5-12 laterals (not clipped/K-IBA) and 4) 6-12 taproots and 1-2 laterals. High concentrations of K-IBA (4000-10,000 ppm) `clipped' unclipped radicles resulting in root systems similiar to those clipped by hand. Stem height was unaffected by treatment. Radicle-clipping may increase stem caliper. K-IBA treatments may decrease root dry weight.

Free access

A manual for certified nursery and landscape professionals has been developed by the University of Minnesota Extension Service in conjunction with the Minnesota Nursery and Landscape Association (MNLA). The purpose of the certification manual is to facilitate the improvement of basic skills and knowledge of nursery and landscape professionals, to further the education and training of competent nursery and landscape professionals, and to serve as a training and reference manual for most levels of nursery and landscape culture and management. The manual consists of thirty-four chapters covering all aspects of woody plant biology and culture: abiotic and biotic plant stress; landscape design; installation and maintenance; plant marketing, merchandising and sales; and laws, regulations and safety concerns for nursery, landscape and garden center personnel. A concise glossary, the American Standard For Nursery Stock, and an illustrated nursery catalog are also included in the manual. The manual is an important part of the MNLA Certification Program whose purpose is to improve the skills, knowledge and, expertise of nursery and landscape professionals. The Certification Program also strives for faster recognition and promotion of professionalism within the industry and to the general public.

Free access

Exogenous ethylene could not substitute for NAA to induce adventitious root initiation in juvenile petiole explants of English ivy (Hedera helix L.), indicating that the action of auxin-stimulated root initiation was not directly mediated through ethylene production. Mature petioles did not initiate roots under any auxin or ethylene treatment combination. Ethephon or ACC supplied at 50 or 100 μm was inhibitory to NAA-induced root initiation in juvenile petioles. The pattern of ethylene production stimulated by NAA application was significantly different in juvenile and mature petioles. Ethylene evolution by juvenile petioles declined to near control levels during from 6 to 12 days after NAA application. Reduction in ethylene production was due to reduced availability of ACC in juvenile petioles. Mature petioles continued to produce ethylene at elevated levels throughout the course of the experiment. Ethylene does not appear to play a significant role in the differential root initiation response of juvenile and mature petioles treated with NAA. However, ethylene appeared to have an inhibitory effect during root elongation stages of adventitious root development in juvenile petioles. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC); 1-napthaleneacetic acid (NAA); 2-chloroethylphosphonic acid (ethephon).

Free access

Several inhibitors of ethylene biosynthesis and action, as well as an atmospheric ethylene scrubber, were used to investigate the role of ethylene in adventitious root initiation in de-bladed petioles from the juvenile and mature phase of English ivy (Hedera helix L.). Induction of root primordia required NAA regardless of the inhibitor treatment. Difficult-to-root mature petioles have been shown to produce higher amounts of ethylene than easy-to-root juvenile petioles. However, mature petioles failed to root under any combination of NAA and inhibitor treatment, indicating that the continued evolution of ethylene in NAA-treated mature petioles was not responsible for the absence of a rooting response. Root initiation in juvenile petioles was not affected by treatment with the ethylene action inhibitors STS and NDE, nor by removal of atmospheric ethylene with KMnO. Inhibition of ethylene biosynthesis using AVG or AOA reduced root initiation in juvenile petioles, but this response was not well-correlated to the observed reduction in ethylene evolution. The inhibitory action of AVG could not be reversed by the addition of ethylene gas or ACC, which indicated that AVG could be acting through a mechanism other than the inhibition of ethylene biosynthesis. Chemical names used: 1-naphthalene acetic acid (NAA); l-aminocyclopropane-l-carboxylic acid (ACC); silver thiosulfate (STS); 2,5-norbornadiene (NDE); aminoethyoxyvinyl-glycine (AVG); aminooxyacetic acid (AOA).

Free access

Abstract

An in vitro system has been developed to study adventitious root initiation in the juvenile and mature phases of English ivy (Hedera helix L.). The system uses de-bladed petiole explants cultured in a defined liquid medium. Adventitious roots are visible macroscopically after 18 days. Juvenile petiole explants show a dose-response to auxin application with optimal root initiation at 100 μM NAA or IAA. With optimal auxin concentration, root initials form in juvenile petiole explants directly from cortical parenchyma cells, which involves induction (1–6 days), meristem organization (6–9 days), and root elongation stages (9–18 days). Sucrose is required for outgrowth of root primordia but not for initiation of primordia. Mature petiole explants respond to auxin with random cell divisions in cortical parenchyma cells; root initials form at a low frequency from callus resulting from this cortical cell division. Distribution of 14C at various times after administration of 14C-labeled NAA is similar in juvenile and mature petioles. Because of their difference in rooting potential, coupled with similarity in anatomical organization, distribution of 14C from NAA, and identical genotype, juvenile and mature petioles provide an excellent experimental system for analyzing the morphogenetic, physiological, and genetic basis of rooting potential. Chemical names used: 1-napthaleneacetic acid (NAA); 1H-indoIe-3-acetic acid (IAA).

Open Access

Abstract

The relationship of foliar injury in Pinus sylvestris (Scots pine) to low temperature and irradiance levels was studied in growth chambers at –l°C(warm) and –7°(cold) under 3 light treatments: 1) nonshaded (1000 watt, Metalarc), 2) 47% shade cloth, and 3) 4-mil white polyethylene. During the 9-week treatment period, plants were tested for hardiness, electrolyte leakage, chlorophyll content, and relative water content. Foliar injury was observed in plants under the cold treatment but the degree of injury was not related to irradiance level. After 6 weeks, electrolyte leakage levels were greater than 50% for all cold-treated plants. No foliar injury occurred on warm-treated plants regardless of light treatment. Minimizing desiccation and rapid temperature fluctuations did not prevent injury. Needle water content of plants from both temperature regimes decreased about 6% over the duration of the experiment. Maximum foliar temperature fluctuations were 5.5° (l.l°/minute) and 4° (0.8°/minute) in the cold and warm chambers, respectively. Although warm-treated plants showed no injury during the treatment period, they deteriorated after several weeks in the greenhouse. Severe root injury to the warm-treated plants may have caused this deterioration.

Open Access

Composting of municipal solid waste (MSW) has received renewed attention as a result of increasing waste disposal costs and the environmental concerns associated with using landfills. Sixteen MSW composting facilities are currently operating in the United States, with many more in the advanced stages of planning. A targeted end use of the compost is for horticultural crop production. At the present time, quality standards for MSW composts are lacking and need to be established. Elevated heavy metal concentrations in MSW compost have been reported; however, through proper sorting and recycling prior to composting, contamination by heavy metals can be reduced. Guidelines for safe metal concentrations and fecal pathogens in compost, based on sewage sludge research, are presented. The compost has been shown to be useful in horticultural crop production by improving soil physical properties, such as lowering bulk density and increasing water-holding capacity. The compost can supply essential nutrients to a limited extent; however, supplemental fertilizer, particularly N, is usually required. The compost has been used successfully as a sphagnum peat substitute for container media and as a seedbed for turf production. High soluble salts and B, often leading to phytotoxicity, are problems associated with the use of MSW compost. The primary limiting factor for the general use of MSW compost in horticultural crop production at present is the lack of consistent, high-quality compost.

Full access

Media fertility is a critical factor in the successful production of container grown plants. Fertility treatments including fertigation and slow-release fertilizers (topdressed and incorporated) were compared. Fertility treatments were studied over a two-year period on a variety of deciduous and evergreen plant materials. Plant growth was quantified based on height, volume, branching, and quality. Soil fertility levels based on leachates were followed during the study. Nutrient release for incorporated fertilizers tested was variable although less so than when the same fertilizers were topdressed. Fertility treatment effects were species-dependent. Several incorporated, slow-release fertilizers, especially those high in nitrogen (Sierra 17-6-10, Sierra High N 24-4-6, Woodace Briquettes 23-2-0, Woodace 21-4-10), show promise for use in two-year container production systems.

Free access

A study was designed to ascertain the efficacy, water use efficiency, runoff potential, and cost effectiveness of four container irrigation systems: overhead sprinkler irrigation, in-line trickle irrigation, capillary mat with leaky hose, and sub-irrigation. Results were species dependent. Plant growth was best under capillary mat and trickle irrigation treatments, however, differences in plant growth and performance between irrigation treatments were minimal. Differences in water use, however, were quite significant. Overhead irrigation was inefficient regarding water use while capillary mat and trickle systems used much lower volumes of water. Conservative irrigation systems which maintain acceptable plant growth using less water and reduce runoff from container production areas can clearly benefit growers by reducing production and environmental costs.

Free access