Most of 36 crabapple and 19 other woody plant taxa demonstrated the ability, when dormant, to grow a continuous row of callus along the cambial region on split-stem pieces within 5 to 7 days of incubation at 25 °C. The ability to grow callus after freezing tests was compared with discoloration and electrical conductivity for determining laboratory freeze injury to selected taxa. Hardiness levels were determined using the procedures of callus growth, discoloration, and electrical conductivity after freezing stem pieces of Jack crabapple [Malus baccata (L.) Borkh. `Jacki'], pink bud Sargent crabapple [M. sargentii Rehd. `Rosea'], Mary Potter crabapple [Malus sp. `Mary Potter'], and snowberry mountainash [Sorbus discolor (Maxim.) Maxim.]. Sampling dates for laboratory freezing tests were chosen to represent midwinter cold hardiness and partial hardiness of either late fall or early spring. There was a high correlation between discoloration and callus ratings for most plants; however, the two methods usually did not identify the same critical temperature (T50) for injury. The critical temperatures identified by callus growth was often 3 to 6 °C lower than for discoloration. For many taxa, callus growth was easier to see than discoloration of cambium and phloem, providing a less subjective evaluation of injury. TTC (2,3,5-triphenyl tetrazolium chloride) treatment was sometimes useful to identify callus growth that died after forming. The critical temperature (Tc), the highest temperature at which relative electrical conductivity differed significantly from the control temperature, was higher in most cases, indicating less cold hardiness than the T50 for callus and discoloration. The callus procedure may have value for evaluating injury to the cambial zone from freezing and other plant stresses because it determines the ability of the plant to continue growth.
Norman E. Pellett and David A. Heleba
Milton E. Tignor*, Gene A. Giacomelli, Tracy A. Irani, Chieri Kubota, Margaret J. McMahon, Sandra B. Wilson, and David A. Heleba
Currently, in the United States, the greenhouse industry covers more than 15,000 acres and is supported by a diverse number of firms with employee expertise that includes greenhouse manufacturing, engineering, irrigation, horticulture, IPM, sales, marketing, and business management. The growing greenhouse industry continues to be in need of highly trained undergraduates that have mastered an amalgam of scientific and business concepts necessary to be competitive in today's agricultural marketplace. Using a multidisciplinary approach we are creating a multimedia instrument for utilization in a variety of greenhouse related courses. This instrument ultimately will be available on the web for anyone to access. To ensure that our vision matches need, we have reviewed the courses offered throughout the United States at 1862, 1890, and 1994 land grant institutions. Course information collected includes; college, Dept., title, level, description, website (if available) and instructor e-mail (if available). Interestingly, there are at least 84 courses offering some aspect of greenhouse science in the U.S. Most are offered in Colleges of Agriculture or Engineering, but are housed in 17 diverse Dept.s. Examples include Dept.s of Horticulture; Agronomy and Horticulture; Agricultural Biosystems and Engineering; Plant, Soil, and Entomological Science; and Horticulture, Forestry, Landscape & Parks. This information will be utilized to focus the instructional design phase of the multimedia instrument, to contact current course instructors for feedback, and to frame future development of the resource.
Milton E. Tignor, Sandra B. Wilson, Lisa S. Hightower, Efren Fitz-Rodriguez, Gene A. Giacomelli, Chieri Kubota, Emily Rhoades, Tracy A. Irani, Margaret J. McMahon, Andrew N. Laing, David A. Heleba, and Sarah M. Greenleaf
Using a multidisciplinary approach, we are creating an instrument for utilization in a variety of greenhouse related courses. We now have over 3 hours of edited and titled video segments that were obtained at different locations by the same videographer. The greenhouse businesses in Arizona, Vermont, Ohio, and Florida were chosen due to their unique business strategies, level of computerization, type of greenhouse construction, management philosophies, and climate challenges. Individual video segments are based on nine topics that were covered at each location including computers, structure, plant life cycle, and labor. The videos have been placed on a streaming media server and will be burned to a DVD. An interactive Flash-based greenhouse environment simulator is nearly complete. This instrument allows students to model greenhouse environments based on climate data from each of the four video locations. Additionally, a searchable digital repository has been established that will allow other participants to submit materials for educational use. This open source software (DSpace) has an integrated distribution license which streamlines compliance with the Digital Millennium Copyright Act. Several hundred high quality images have already been uploaded, described and tagged. Learning assessment tools based on numerical self-evaluation and verification narratives are also being developed in conjunction with the multimedia tools. We have created a database of all the greenhouse courses at 1862, 1890, and 1994 institutions and hope to build a community of teachers that will utilize and contribute to the multimedia greenhouse collection. This community has already grown to include two international greenhouse experts who contributed interactive software for educational use.