Search Results
You are looking at 1 - 10 of 16 items for :
- Author or Editor: Kenneth R. Schroeder x
- HortScience x
According to brain-based learning theory, learning is enhanced by challenge and inhibited by threat. Effective learning occurs when students are immersed in the educational experience, challenged yet not threatened, and encouraged to actively process information. All of these components are part of simulation or role-play games. With these basic concepts in mind, we approached the challenge of enhancing student learning in a plant identification course taught in a large class setting. Considering that plant identification requires some basic detective skills, and the popularity of criminal investigation television programming, we designed a role-play exercise involving case files, investigation zones, and detective teams. As a spin-off from the television shows “CSI: Crime Scene Investigation” and “CSI: Miami,” the exercise was coined “CSI: Manhattan, Conifer Site Investigation in Manhattan, Kansas.” It was designed to fit into a 50-minute class period. Throughout the exercise, detective teams (students) needed to collectively locate and identify plants based on previous knowledge and clues within the case files and at the sites. Upon completion, plant specimens were checked in and identification logs discussed in order to provide immediate feedback and reinforcement of learning. Students enjoyed the exercise, offering positive feedback and conversations about the exercise throughout the balance of the semester. Six months later, while walking past one of the investigation sites, students remembered the site, exercises performed, and the plant name. The exercise includes both interactive and experiential learning components. This session will discuss the “CSI” exercise and its value in linking action to information.
Hypocotyls from Antirrhinum majus L. were excised at 2 weeks of age from seedlings grown under a 16-hour photoperiod or continuous darkness. Explants were cultured on modified Murashige-Skoog (MS) medium containing 0, 0.44, 2.22, 4.44, 8.88, or 44.4 μm BA to investigate adventitious shoot formation. Excised hypocotyls from eight commercial cultivars, three inbred lines, and an F1 hybrid between two of the inbreds were cultured on MS medium containing 2.22 μm BA to assess genotypic effects on adventitious shoot formation. The influence of seedling age was assessed by excising hypocotyls from seedlings at 6, 10, 14, 18, 22, 26, or 30 days. Optimal conditions for adventitious shoot formation on excised hypocotyls included: seedling growth in a lighted environment, use of hypocotyls from 10-day-old seedlings, and culture on medium containing 2.22 μm BA for 3 weeks. Under these conditions, up to a 5-fold improvement in number of shoots per hypocotyl over previous studies was achieved. Adventitious shoot formation was genotype-dependent and appeared to be a dominant trait. Chemical name used: N 6-benzyladenine (BA).
Leaf impressions were made from two short-lived (4 and 5 d) inbreds, a long-lived (11 d) inbred, and their hybrids (8 and 9 d) of Antirrhinum majus L. using Super Glue and glass microscope slides. Leaves were taken from mid stem, pressed on glass slides (under side down), spread with a small amount of Super Glue, set for 3 to 4 s. Then, the leaf was peeled off leaving a permanent impression in the glue. Slides were placed under a microscope equipped with a video imaging system and computer images were taken to facilitate counting of stomatal complexes. Number of stomata ranged from 10,400 to 21,300 per cm2 of leaf. A LI-COR LI-3100 area meter (LI-COR, Inc. Lincoln, Neb.) was used to measure total leaf area of 40-cm cut flower stems of each accession. Stomata per flowering stem ranged from 1,074,000 to 2,282,000, with the long-lived inbred having the fewest stomata, the hybrids intermediate with 11% to 21% more, and the short-lived inbreds having 40% to 113% more stomata per stem. It appears long postharvest life of A. majus is associated with flowering stems with fewer stomata per cut stem.
A phenol-sulfuric acid assay was used to quantify non-specific neutral carbohydrates in Antirrhinum majus L. flowering stems of three inbreds and their hybrids. Flowering stems 40 cm long were harvested with five to six florets open and flower, leaf, and stem tissue separated, freeze-dried, and finely ground. Carbohydrates were extracted from the tissue with 95% ethanol in a 70 °C water bath and combined with a 5% w/v phenol solution and concentrated sulfuric acid. Glucose equivalents were determined with a spectrophotometer at absorbance of 490 nm. Averaged over tissue type, results were genotype dependent, ranging from 213 to 291 μg glucose equivalent per mg dry tissue with a LSD0.05 = 13. Flowers had the highest concentration of 340 μg/mg dry tissue, followed by stems, then leaves with 36% and 38% lower concentrations, respectively. Carbohydrate concentrations in two inbreds were compared when grown under cool (16 °C) and warm (29 °C) conditions. A genotype x environment interaction exists with inbred 3 exhibiting no reduction, 6% increase, and a 45% reduction in carbohydrate concentration when grown in warm conditions, while inbred 2 exhibited 15%, 23%, and 37 % reductions for flowers, leaves, and stems, respectively. Overall, there were 10% and 21% reductions in carbohydrate concentration for inbreds 2 and 3, respectively, when plants were grown under warm conditions.
Efforts to improve postharvest longevity of fresh-cut flowers has only recently turned toward selection and breeding. Conventional methods to extend keeping longevity of cut flowers depend on use of chemical treatment placed in holding solutions. Postharvest longevity studies were initiated with Antirrhinum majus L. (snapdragon) to determine: if natural genetic variation existed for cut-flower longevity, the inheritance of the trait, heritability, and associated physiology. Evaluation of commercial inbreds held in deionized water revealed a range in cut-flower longevity from a couple of days to 2.5 weeks. The shortest- and longestlived inbreds were used as parents in crosses to study the aforementioned areas of interest. Information will be presented on inheritance of cut flower longevity based on populations evaluated from matings for generation means analysis and inbred backcross method. Also presented will be information on stomata, transpiration, carbohydrate, fresh-weight change, and forcing temperature relative to postharvest longevity.
Flowering stems from three commercial inbreds and their F1 hybrids of Antirrhinum majus L. were cut when the first eight basal florets opened. Tops of the stems were removed above the eighth floret and florets were removed leaving two, four, six, or eight open florets on a stem. A completely random design with 10 replications was used. Flowering stems were placed in plastic storage containers 35 × 23 × 14 cm (L × W × H) with 2.5 L deionized water for postharvest evaluation. Evaluation took place under continuous cool-white fluorescent light (9 μmol·m–2·s–1) at 24°C Postharvest life was determined as the number of days from cutting to discard when 50% of the open florets on a flowering stem wilted, turned brown, or dried. Results showed postharvest life increased as the number of open florets on a stem decreased. Mean postharvest life increased as much as 4.7 days when only two florets remained on a stem. These results indicate a direct relationship between number of florets on a cut flower stem and postharvest life.
One-centimeter hypocotyl explants from 2-week-old Antirrhinum majus L. (snapdragon) seedlings germinated and grown in vitro under 12-h cool-white fluorescent light and 12 h dark or 24 h dark were placed on Murashige and Skoog (MS) medium containing 0, 0.44, 2.22, 4.44, 8.88, or 44.4 μM N6-benzyladenine (BA). Cultures were maintained under the light/dark regime at 25°C. After 2 weeks, adventitious shoots were counted. A shoot was considered adventitious and counted if a stem and leaf developed. Shoots developed along the entire length of the hypocotyl sections. Mean shoot production per hypocotyl explant ranged from 2.4 to 6.1 shoots when seedlings were germinated and grown in 24 h darkness and 2.2 to 10.9 shoots when started in the light/dark regime. Highest shoot counts were attained /from hypocotyl explants when seedlings were germinated and grown under the light/dark regime for 2 weeks and transferred to 2.22, 4.44, or 8.88 μM BA. Shoot development appeared normal at the 2.22 and 4.44 μM level, while at 8.88 μM BA, development was slightly abnormal along with slightly more callus production.
Cut flowers of a short(S) lived (3 days) inbred, a long(L) lived (15 days) inbred and their hybrid (F1, 7.3 days) of Antirrhinum majus L. were evaluated for water loss when held in deionized water under continuous fluorescent light at 25°C. Flowering stems for water loss evaluation were harvested when the basal five to six florets expanded. Cut stems were placed in narrowed-necked bottles with the open area between the stem and bottle sealed with Parafilm. Stem weight and water weight in the bottle were taken every 24 h. Water loss evaluation was continued until 50% of the open florets on the flowering stem wilted or turned brown. Overall, water loss from all accessions was highest 24 h postharvest, declined rapidly between 24 to 96 h, and remained unchanged throughout the remainder of postharvest life. Between 24 to 96 h, the slope of the line for water loss was greatest for L, least for S, and intermediate for the F1. It appears that longest postharvest life of A. majus is associated with the most rapid decline of water loss immediately postharvest to a level, which remains constant.
Postharvest longevity (PHL) is important in determining quality and consumer preference of cut flowers; thus, it remains a pressing problem for the florist industry. Information on genetics and heritability of cut flower PHL is lacking. This study focused on determining gene numbers and inheritance of Antirrhinum majus L. cut flower PHL. An inbred backcross population was generated from a yellow short-lived (YS; 6d PHL) and a white long-lived (WL; 14 d PHL) inbred. F1 hybrids were backcrossed reciprocally three times to each parent. Parental backcross (BC) populations contained 55 to 65 lines. Lines within each BC generation were self-fertilized three generations by single-seed descent without selection to produce BC1S3, BC2S3, and BC3S3 generations. Cut flowers from all generations were evaluated together for PHL in deionized water. Gene numbers were estimated using confidence intervals and the proportion of non-parental BC lines. Continuous variation, estimates of a minimum of two to four genes controlling PHL, and significant environmental variation suggest selection for increased PHL would be successfu,l but slow. A negative correlation between PHL and yellow flower color was detected in this study. In spite of that fact, mean PHL of the yellow flowered inbred lines improved 1 to 2 d when backcrossing to YS and 3 to 4 d when backcrossing to WL without selection. Thus, inbred backcrossing to a long-lived parent with selection for flower color should make acquisition of longlived colored lines attainable.
Leaf explants of Nicotiana alata Link and Otto. were surface disinfested and cultured on Murashige and Skoog (MS) medium containing 2.66 μm N6-benzyladenine (BA) to promote shoot proliferation. After 5 weeks, proliferated shoots were removed and remaining callus saved. Callus was inoculated with Agrobacterium tumefaciens encoding a senescence-specific promoter SAG12 cloned from Arabidopsis thaliana fused to a Agrobacterium tumefaciens gene encoding isopentenyl transferase which catalyzes cytokinin synthesis. Following inoculation, the callus was cocultivated for 6 days on BA medium. Selection for transgenics was done on BA medium plus 100 mg Kanamycin and 400 mg Ticarcillin (antibiotics) per liter. Proliferating shoots were rooted on MS medium containing antibiotics. Rooted cuttings were transplanted to soil, acclimated and flowered in the greenhouse. Transgenics were outcrossed to a commercial N. alata hybrid. Seed was germinated in vitro on half-strength MS medium plus antibiotics. Segregation of transgenics to nontransgenics was 1:1. Evaluation of leaf senescence on 5-month-old plants showed 2 to 14 times fewer senesced leaves on the transgenic than the nontransgenic plants.