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- Author or Editor: Frederick T. Davies x
Abstract
During 1982, the Propagation Working Group (ASHS) conducted a survey on the content and organization of plant propagation courses. The survey, sent to 112 major colleges or universities, was composed of 4 sections: 1) general information, 2) course organization, 3) course content, and 4) evaluation. The following results were compiled from 28 completed forms.
Arbuscular mycorhizal fungi (AMF) have been used in phytoremediation and can increase tolerance and growth of plants in contaminated environments. However, little is known about the influence AMF on plant growth to organic contaminants in soils. A greenhouse experiment was conducted to study the response of seedlings of annual ryegrass (Lolium perenne L.) var. Passerel Plus inoculated with Glomus intraradices Schenck & Smith in soil contaminated with sweet Arabian median crude oil. Inoculated (AMF) and non-inoculated (Non-AMF) plants were established in an pasteurized and artificially contaminated sandy loam soil with 0; 3000; 15,000; or 45,000 mg of petroleum kg-1 soil (n = 20). Plants were inoculated with 500 spores of G. intraradices (MycoriseĀ® ASP, PremierTech Biotechnologies, Canada). After 90 days, plant growth of AMF or Non-AMF plants, was drastically affected at all petroleum concentrations. However, G. intraradices enhanced plant growth, chlorophyll content, and gas exchange of plants grown at 3,000 mg kg-1 compared to Non-AMF plants. Total leaf area, chlorophyll, and net photosynthesis were also higher (+380%, +63%, and +81%, respectively) at this concentration. Water use efficiency (net photosynthesis/stomatal conductance) of AMF-plants was three times greater than Non-AMF at 3,000 mgĀ·kg-1. At concentrations of 15,000 and 45,000 mg kg-1 AMF did not have effect, but colonization was observed (11.8% and 18.6%, respectively). These values of colonization were significantly lower than those observed in AMF-plants at 0 (42.5%) and 3,000 mgĀ·kg-1 (55.6%). Studies are currently being conducted to understand the physiological role of AMF on plants exposed to organic contaminants.
A phytoremediation study in a 3 Ć 3 Ć 2 factorial experimental design was conducted to determine the effect of Glomus intraradices (AMF) inoculation and inorganic fertilization on the growth and development of Lolium multiflorum cv. Passarel Plus, and on the degradation of total petroleum hydrocarbons (TPH). The 80-day study was done with pots containing sandy soil. Seedlings of L. multiflorum were transplanted to uncontaminated or soil contaminated with Arabian crude oil (ACO) at concentrations of 3000 and 15,000 mgĀ·kg-1. Half of the seedlings were inoculated with 500 spores of AMF. Plants were fertilized with Long Ashton Nutrient Solution (LANS) at 0.5Ć, 1.0Ć, or 2.0Ć strength, modified to supply 30 Ī¼gĀ·mL-1 P to maximize the AMF establishment. Total plant dry weight and leaf antioxidant activity were reduced by ACO when compared to control plants. The LANS fertilization enhanced plant growth under ACO-contamination, and allowed similar antioxidant activity in plants exposed to 15,000 mgĀ·kg-1. Soil rhizosphere respiration was increased by LANS, particularly with 15,000 mgĀ·kg-1 ACO. AMF inoculation did not enhance plant growth, antioxidant activity, or microbial respiration. The average root colonization was around 30% in contaminated and uncontaminated rhizospheres, indicating that the tolerance of AMF symbiosis to ACO. Greater TPH degradation was achieved in non-AMF plants at 3000 mgĀ·kg-1 ACO in combination with 0.5Ć LANS. LANS-fertilization with 1.0Ć or 2.0Ć did not enhance TPH-degradation when compared to 0.5Ć LANS.
A mobile web application called PropG was developed for students to quickly access more than 270 glossary terms defined in a plant propagation textbook. The functionality and usefulness of the app was evaluated by 53 students enrolled in a semester-long online course in plant propagation. Means of pre- and post-test responses to 17 knowledge items showed students perceived a significant knowledge gain in the course for each of the subject categories evaluated. Most students agreed or strongly agreed this learning tool was organized and easy to navigate and would use it in the future. Since 2021, PropG received 153,645 total page views, 90,818 unique visits, and 17,216 returning visits, showing its widespread use in plant propagation.