Softwood shoots can be forced from sections of branches of trees or from basal stems of shrubs by cutting into ≈40-cm lengths and placing these segments horizontally in flats filled with perlite. We have had our best success using stems that are >1.5 cm in diameter. Although the best environment that we have found for producing the most and longest softwood shoots is under intermittent mist, this is unacceptable for producing explants because of microbial contamination. Rather, for micropropagation, watering must be done two to three times a day and care must be taken to avoid water spray onto the stem segments or the subsequent softwood growth. Irrigation can be by hand or by using drip irrigation. For trees, using the basal portions of large branches allows for selection of shoots from within the “cone of juvenility.” Theoretically, these should propagate better than shoots taken from the outer, more adult portions. Although late winter through spring are the best times for forcing, some shoots will grow if the stem sections are harvested nearly any time of the year, except for October through December in southern Illinois.
John E. Preece
John E. Preece
In an effort to improve higher education, most states now require non-graded assessment of students enrolled in publicly funded universities. Assessment may be across the curriculum or within a major at graduation, yearly, or during individual courses or lectures. I have used two assessment techniques in my classroom that are effective and require a minimum of time. These techniques encourage student participation in class and allow for non-graded anonymous assessment in a manner that the students take very seriously. During the first class of the term students are handed filing cards and given 5 minutes to write their course objectives. By comparing their objectives with mine, I am able to react to student interests and needs in a constructive manner. At the end of one out of three lectures per week, students are given 1-2 minutes to write the “muddiest point” of the day's lecture. This enables the instructor to determine which points need further clarification. Discussion will focus on these techniques and their implications for learning horticulture at both the graduate and undergraduate levels.
John E. Preece
Two nongraded techniques are described that assess student expectations and learning in horticulture classes. These involve anonymous, in-class student responses that can encourage and enhance interaction, communication, and learning without being a burden to the instructor. During the first class meeting, students were given 5 minutes to write their course objectives onto filing cards. By summarizing their objectives, reviewing them with the class at the beginning of the next period, and comparing their objectives with mine, I was able to react to student interests and needs in a constructive manner. About once per week at the end of a lecture, students were given 3 minutes to write the “muddiest point” of that lecture. This enabled me to clarify points orally, in writing, or by specific reading assignments. If the instructor responds in a timely manner, these assessment techniques will be taken seriously by the students. Such techniques can increase interest, understanding, and the perception that students can have a positive influence on the quality of their instruction.
Sharon Bates and John E. Preece
At three different times throughout the growing season, white ash seeds representing different maturity levels were transversely dissected, surface sterilized, and placed on agar-solidified MS medium containing 10 μM thidiazuron (TDZ) and a factorial combination of 0, 1, and 5 μM 2,4-D and 0, 0.5, and 1 μM glyphosate. After four weeks, explants were transferred to MS medium containing 5 μM BA and 5μM NAA. After 12 weeks in vitro, the greatest percent (60%) of explants with organogenesis (adventitiously produced leafy structures that could grow into shoots) was when seeds were exposed to 1 μM 2,4-D. Organogenesis occurred on explants only exposed to TDZ (31%), therefore auxin was not necessary for, but enhanced organogenesis. Seed explants were not consistently stimulated, or inhibited by these levels of glyphosate. Compared to immature-seeds, mature see explants were the most organogenic (67%) and had the greatest amount of adventitious shoots (14%).
Kathryn Keeley and John E. Preece
Hard-to-root hardwood cuttings of Vitis aestivalis `Norton' were collected during Feb. 1999. Cuttings had three nodes and were 10 to 15 cm long. Prior to treatments, cuttings were submersed in a solution of 9.5 g/1L of ZeroTol (a mixture of hydrogen dioxide and peroxyacetic acid). The bottom two nodes were placed into 1 vermiculite: 1 perlite (by volume) and set under mist in the greenhouse at of 20/15 °C day/night). About 5 weeks after treatment, number of roots and root length data were collected. The bottom 2 cm of cuttings in one experiment received a 30-s dip in 0, 2500, 5000, 7500, or 10,000 mg/L IBA and/or NAA to determine the effects of these treatments on rooting of hardwood cuttings. IBA and NAA are not significantly different, however there was a positive linear relationship between rooting and concentration of auxin. As concentration of auxin increased, mean number of roots increased. In additional experiments, cuttings treated with 0 or 5000 mg/L of IBA were compared based on timing after harvest of cuttings and treatment. Of the cuttings treated and placed under mist on 26 Mar. 1999, 30% of the control cuttings rooted and 50% of the cuttings treated with 5000 mg/L rooted. Two weeks later, 65% and 55% of the cuttings treated with 5000 mg/L rooted respective to the 0- and 5000-mg/L treatments. One week later (14 Apr. 1999), 77.5% and 72.5%, respectively, rooted. This suggests that timing after harvest for placing the cuttings in a propagation bed is important for increasing the rooting percentage of `Norton' hardwood cuttings.
John E. Preece and Gale McGranahan
Luther Burbank began making controlled crosses between walnut species in the late 19th century after hearing about a “supposed natural European hybrid walnut.” He crossed Juglans hindsii (northern California black walnut) × J. regia (Persian walnut) and produced progeny that he named ‘Paradox’ because of its extremely fast growth and other “anomalies.” He also crossed two American species, J. hindsii × J. nigra (eastern black walnut), producing ‘Royal’ walnut progeny that were fast-growing and prolific nut producers. A third interspecific hybrid was a cross between J. ailantifolia (Japanese walnut) × J. regia that resulted in extremely vigorous progeny but was not named. He observed segregation in the F2 populations and described giants and dwarfs as reversions to ancestral forms. Luther Burbank also made selections for walnut scion cultivars and was especially interested in thin-shelled nuts. He collected seeds from a J. regia growing in San Francisco because it produced regularly and had very high-quality nuts with relatively thin but poorly sealed shells. He selected one of its seedlings as ‘Santa Rosa Soft-Shell’ and described it as bearing large crops of nuts that were nearly white with thin shells and delicious white meat. Burbank’s contributions to the walnut industry endure to this day, especially through the widespread use of seedling and clonal ‘Paradox’ walnut rootstocks.
Katayoun Mansouri and John E. Preece
A factorial combination of gibberellic acid (GA3) and benzyladenine (BA) was applied in 20% white exterior latex paint to large (40 cm long, >2.5 cm diameter) stem segments of Acer saccharinum L. (silver maple) to determine the effects on forcing new softwood shoots in the greenhouse or laboratory and the subsequent growth of these new shoots in vitro. Stem segments were harvested from 10-year-old field-grown coppice shoots. The GA3/BA-paint mixes were applied to the entire stem segments that were forced in plastic flats filled with 1 perlite: 1 vermiculite (by volume) and watered with care so as not to wet the new softwood shoots. The flats and stem segments were drenched weekly with Zerotol (0.18% H2O2). The softwood shoots were harvested when they were at least 3 cm long. After disinfesting and rinsing, the nodal and shoot tip explants were established aseptically in vitro on DKW medium with no cytokinin or with 10-8M thidiazuron. Coppice shoots were harvested, cut, and painted on 9 Sept., 28 Oct., and 12 Dec. 2005. Although there were no significant differences in shoot production among stem segments painted with various combinations of GA3/BA, stems treated with plant growth regulators produced a mean of 2.7, 1.8, or 0.5 shoots for the three harvest dates compared to 0.5, 0.0, or 0.25 shoots on control stem segments. It is well-known that shoot forcing is poor from September through January; however, use of GA3/BA resulted in growth of dormant epicormic shoots. Shoot tip explants produced the most shoots in vitro after 8 weeks if they were harvested from stem segments treated with 0.03 mM GA3, whereas nodal explants produced the most shoots if harvested from segments that had been treated with 0.01 mM GA3.
Ksenija Gasic and John E. Preece
Paul E. Cappiello and John E. Preece
A single clone of Acer saccharinum was selected and propagated from each of 15 provenances across the plant native range. The clones were field grown in Carbondale, Ill., during the study period. Plants were sampled during Winter 1992-93 and 1993-94 and assayed for low-temperature tolerance. During both winters, plants exhibited greatest variation in tolerance around the November and April sampling dates. In midwinter, there was little variation observed and 13 of 15 clones were tolerant to at least -40C. The relationship among Acer saccharinum provenance and cold tolerance curves will be discussed.