Changes in volatile terpene and diterpene resin acid composition of resistant and susceptible white spruce leaders exposed to simulated white pine weevil damage

Induced (traumatic) resin in white spruce (Picea glauca (Moench) Voss) leaders resistant or susceptible to the white pine weevil (Pissodes strobi Peck) was analyzed for volatile terpenes and diterpene resin acids after simulated white pine weevil damage. Leaders from 331 trees were wounded just below the apical bud with a 1-mm diameter drill, coinciding with the natural time of weevil oviposition in the spring. Leaders were removed in the fall, and the bark and xylem from the upper and lower regions of the leader extracted and analyzed by gas chromatography. Unwounded trees had low amounts of resin in xylem compared with bark. In response to wounding, volatile terpenes and diterpene resin acids increased in the upper xylem (area of wounding), with resistant trees showing a greater increase than susceptible trees. Wounding caused monoterpenes in particular to decrease in the lower region of the leader (away from the drilled area) in greater amounts in susceptible trees than in resistant trees. In response to wounding, the proportion of monoterpene to resin acid increased in the upper and lower xylem of resistant trees, and slightly increased in the upper xylem of susceptible trees. Monoterpene-enriched resin is more fluid than constitutive resin, and probably flows more readily into oviposition cavities and larval mines, where it may kill immature weevils. Loss of resin components in the lower xylem suggested catabolism and transport of these materials to the site of wounding; however, energetic and regulatory data are necessary to confirm this hypothesis. This study provides a basis for measuring the ability of a tree to undergo traumatic resinosis that could be used to screen for resistance to white pine weevil.     

Spectrophotometric determination of polyacrylamide in waters containing dissolved organic matter

Using polyacrylamide (PAM) to reduce soil erosion in irrigated land has increased rapidly in recent years. A simple and reliable method to measure the PAM concentration in waters containing dissolved organic matter (DOM) is of great importance in assessing the fate and efficiency of PAM application. In this research, an analytical method to determine the PAM concentration of waters with correction for DOM interference was developed and tested. The method is based on a combination of determining the total concentration of amide groups by the N-bromination method (NBM) and determining the DOM content spectrophotometrically. The total concentration of amide groups of both PAM and DOM was determined by NBM at 570 nm. The DOM moiety, which is proportional to DOM concentration, was determined by spectrophotometry using a UV 254-nm wavelength. The actual PAM concentration of a water sample (soil extract containing PAM in this study) was obtained from NBM readings subtracted by the interferential DOM contribution using a correction curve. Analysis of PAM in two soil-water samples showed that the recoveries ranged from 94 to 100.3% for the 2 mg/L PAM sample and from 98.4 to 101.4% for the 10 mg/L PAM sample with various DOM concentrations. The coefficients of variation were <6% in all cases.     

Use of Internet-based resources to support an introductory animal and poultry science course.

This article describes the development and implementation of a World Wide Web page to support a team-taught introductory animal and poultry science course. The objectives were to examine the capabilities of this type of instructional resource, determine students' willingness to use this type of resource, create opportunities for interactive learning, and improve students' enthusiasm for the subject area. A variety of course materials were made available through the Internet, including the class syllabus, lecture notes, and practice questions to support and augment class lectures. Additional on-line resources included a bulletin board for instructor announcements, a list-serve for student discussions concerning administrative and educational issues arising during the semester, a class E-mail list, and a page with links to other sites of agricultural interest. Materials were accessible from a variety of computer resources, including campus computing laboratories, dial-up access, and access via other Internet service providers. Use of the materials was evaluated by analysis of log files from the server. Effectiveness of the resources was determined from surveys of students conducted before and after implementation of the on-line resource. Students indicated that the most useful components of the Web page were the class notes and practice/review questions. Effectiveness of the site was related to the amount of material available through the site, the level of interaction, whether the task was required, and the ease of access to computers and the Web site. Student evaluations indicated that this form of instructional supplement is a viable method for enhancing the learning experience in the introductory animal sciences.