A METHOD TO SCREEN WEED-SUPPRESSING ALLELOCHEMICALS IN FLORIDA BIOMASS
Wood chip mulches derived from woody species grown in Florida are sometimes used for weed suppression in perennial fruit crops, especially in sustainable and organic production systems. A method for testing allelopathic qualities of these materials was developed, including wood chip incubation and filtering followed by bioassays of lettuce seed germination and growth. Eluates of wood chips from red maple ( Acer rubrum cv. ‘ Rubrum ’ L.), swamp chestnut oak ( Quercus michauxii Nutt.), red cedar [ Juniperus silicicola (Small) E. Murray] and sweet bay ( Magnolia grandiflora L.) highly inhibited germinating lettuce seeds, as assessed by germination percentage, radicle and hypocotyl growth. The effects of eluates from these four species were more than or equal to that found for eluates from wood chips of black walnut ( Juglans nigra L.) a species with a high level of allelopathic activity. In the United States annual estimated waste biomass of urban tree and wood mill residues totaled 38,000 and 5,600 dry metric tons, respectively (National Research Council, 2000). Wood chip mulches from such biomass applied as a preor post-plant treatment have been shown to suppress weeds (Autio, 1999), moderate soil temperature (Harris, 1983), soil moisture (Russel, 1939), and increase growth of young pecan trees (Foshee et al., 1996; Smith et al., 2000). Experiments to determine allelopathic activity of woody species and their derived materials have included interplanting corn with black walnut (Jose et al., 1995) and application of plant tissue extracts to weeds growing in the field (Al-Saadawi and Al-Rubeaa, 1985; Al-Saadawi et al., 1985). Other laboratory studies assessing allelopathic activity of cover crops have used germinating lettuce seeds as a test crop because of its high sensitivity to bioactive substances (Fujii and Shibuya, 1992). Our objective was to test a laboratory bioassay for allelopathic chemicals from wood chips of species commonly found in woody biomass waste management operations. Once developed, such a laboratory bioassay could be used to evaluate biomass allelopathic potential prior to longer term field trials. This research was supported by the Florida Agricultural Experiment Station and approved for publication as Journal Series No N-02514. This research was supported by a grant from the University of Florida Center for Biomass Programs. 1 Corresponding author
Allelopathic effects of juglone on germination and growth of several herbaceous and woody species
Laboratory experiments were conducted to determine juglone sensitivity of 16 species (Trifolium incarnatum, Coronilla varia, Vicia villosa, Lespedeza stipulacea, L. cuneata, Acer ginnala, Caragana arbor-escens, Elaegnus angustifolia, E. umbellata, Lonicera maackii, Quercus alba, Fraxinus americana, Liriodendron tulipifera, Alnus glutinosa, Pinus strobus, andP. sylvestris) being considered for mixed plantings withJugions nigra (black walnut). All species were sensitive to juglone, but seed germination and radicle elongation were less affected than shoot elongation and dry weight accumulation. Seed germination and radicle elongation were affected by juglone in 6 and 11 species, respectively, mainly by the higher concentrations (10−3 M and 10−4 M). Shoot elongation and dry weight accumulation of all species were affected by juglone; many species were sensitive to concentrations as low as 10−6 M. Seedlings of all species were severely wilted and eventually killed by 10−3 M juglone, and most were chlorotic and severely retarded by 10−4 M juglone. Seedlings inhibited by 10−6 M and 10−5 M juglone did not showany visible signs of injury. Based on the effects on seedling shoot elongation and dry weight accumulation, the five species found to be most sensitive to juglone were:Lonicera maackii, Lespedeza cuneata, Trifolium incarnatum, Alnus glutinosa, and Elaeagnus umbellata.
The measuriment of ferromagnets magnetic characteristics using Labview software
The digital method of measurement and registration of dynamic loops hysteresis family of magneto-soft materials where, along with known analogues from electro-technical steel, magnetic materials with considerably smaller specific magnetic losses such as amorphous alloys on the basis of iron, is offered. Tests of magnetic properties of materials are carried out on the base of the hardware-software measuring complex in which along with the standard established electric equipment and USB oscillograph for realization of a digital method, the software for the personal computer developed in the environment of visual programming of Borland Delphi 7.0, connected through the ActieveX technology with the Labview 7.0 environment, is applied. The software allows carrying out input of basic data concerning geometry of prototypes of cores from magnetic materials and numbers of rounds of the magnetizing and measuring windings located on their surface. Experimental data on voltage at measuring winding terminals are processed by means of the virtual integrator in a Labview package. The developed software provides the possibility of saving the obtained hysteresis loop in the form of a text file, and creation of the hysteresis loops family on the virtual oscillograph screen.