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- Author or Editor: Sven E. Svenson x
Students enrolled in three different horticulture courses were given traditional, in-class exams. After the in-class exams were completed, students were given another copy of the same exam to complete as a take-home test. Their final overall score was weighted as 65% for the in-class exam, and 35% for the take-home. During the process of completing the take-home portion, students identified incorrect responses written on the in-class exam. The self-identified errors helped the students remember correct information on subsequent final exams. Students participating in the second-chance procedure scored over 5% higher on comprehensive final exams. The procedure has many variations, including written- defenses of selected responses, but it requires the allocation of additional time by the instructor.
Influence of uniconazole (UNI) and benzylaminopurine CBA) on flowering and growth of Acalypha hispaniolae was evaluated. Drenches of UNI at 0.02, 0.1 and 0.2 mg ai per pot, and foliar application of 112, 225, or 450 mg BA/liter were applied 4 weeks after potting. UNI applied at 0.02 mg ai increased number of racemes produced 5 and 10 weeks after treatment, but did not influence shoot growth or stem length. At higher rates, UNI reduced flowering and growth. Application of 450 mg BA/liter increased number of racemes and shoot growth 5 weeks after treatment, but not 10 weeks after treatment. The best combination of rapid shoot growth, increased number of racemes, and increased size of racemes resulted from the interactive application of 0.02 mg ai UN1 per pot and 450 mg BA/liter. Better growth management might be obtained from a refinement of the concentration ranges studied.
Rooting and growth of Verbena cuttings (Verbena × hybrids Voss) were measured to determine response to foliar-applied benzylaminopurine (BA). There was no rooting response to BA application when visible nodal roots were present at the base of the cutting. There was no response to 30, 100, or 300 mg BA/liter applied to the foliage 48 or 96 hours after excision from the stock plant. Rooting-zone dry mass, total cutting dry mass, and number of roots were increased by 30 mg BA/liter applied immediately after excision when there were no visible nodal roots at the base of the cuttings. Foliar application of BA at 10 or 30 mg·liter-1 increased lateral bud elongation of subsequently rooted shoots by 20% and 49%, respectively. Application of BA during cutting propagation to enhance subsequent lateral bud elongation does not appear to inhibit rooting in Verbena stem cuttings. Chemical name used: 6-benzylaminopurine (BA).
The objective of this study was to determine if shading and DCPTA application interactively influence seedling emergence and shoot growth of Hypoestes phyllostachya Bak. seedlings. Hypoestes `Carmine Red' seeds were soaked for 6 h in distilled water, and then soaked 6 h in solutions containing' 10 mg DCPTA/liter (30 mM) and 0.1% Tween-80, 0.1% Tween-80, or distilled water. Date of seedling emergence was recorded after sowing (0.5 cm) in 9-cm (460 ml) pots filled with 440 ml of a 5 pine bark: 4 Florida sedge peat: 1 sand medium. Forty pots from each of the three seed-soak treatments were grown under 30%, 63%, or 84% shading, provided by saran-type shadecloth, using natural photoperiods (completely randomized design). Shoot heights and dry weights were recorded 75 days after sowing. Neither shading nor DCPTA influenced total seedling emergence or seedling emergence rate (time to 50% emergence). Under 30% shading, seedlings from DCPTA-treated seeds were taller and had more shoot dry weight than seedlings from surfactant- or water-treated-seeds; however, DCPTA did not influence seedling height or shoot weight under 63% or 84% shading.
Shoot and root growth responses of `Cunningham's White' rhododendron (Rhododendron x) was studied when grown in black plastic or molded fiber pots treated with copper hydroxide, or not treated. Containers of two sizes were studied, and the influence of pot type on substrate temperature was recorded. Rhododendron shoot height and dry weight was not influenced by pot volume, pot type, or copper treatment at 49, 131, or 362 d after potting. Rhododendron shoots were larger when grown in 3.8-L (trade 2-gal) pots compared to 2.8-L (trade 1-gal) pots, or when grown in 3.8-L fiber pots compared to 3.8-L plastic pots, both 131 and 362 d after potting. Copper treatment did not influence shoot size. Copper treatment reduced the amount of circling or matted roots at the container-substrate interface for both plastic and fiber pots, but there was better control of root growth in 3.8-L pots compared to 2.8-L pots. Substrate average minimum temperatures were warmer, and average maximum temperatures were cooler when pots were located near the center of the growing block compared to the southwest corner ofthe growing block. Substrate average maximum temperatures were cooler in fiber pots compared to plastic pots, but only when pots were located on the southwest corner of the growing block.
Extensive growth of liverwort (typically Marchantia sp.) on the surface of the growing medium in plant containers is a serious problem in many nursery and greenhouse operations. A spray application of cinnamic aldehyde at 0%, 0.25%, 0.5%, or 1% a.i. was applied to uninfested 4-inch-diameter containers, and to containers infested with Marchantia polymorpha. Application to uninfested containers delayed liverwort establishment for an additional 1, 2, and 4 weeks at the 0.25%, 0.5%, and 1% applications rates, respectively, compared to the 0% control. Ten days after application, 0%, 70%, 95%, and 100% of liverwort thalli covering the growing medium surface of infested containers were killed by the 0%, 0.25%, 0.5%, or 1% application, respectively. However, only the 1% rate also killed the gemmae cups growing on the thalli surface. Regrowth of liverwort began 2, 3, and 5 weeks following application, respectively. Prevention of infestations is desirable, as dead liverworts are less attractive than live growth. No phytotoxicity symptoms were observed on Rhododendron growing in the treated containers.
The influence of no shading; 30%, 47%, or 63% black polypropylene stationary shading; and white poly retractable shading (50% shade operated to provide morning “cold trapping”) on substrate temperature was studied for Coreopsis verticillata `Zagreb' and Forsythia `Lynwood' growing in 2.75-L black polycontainers filled with an unamended Douglas-fir bark substrate. The southwest region of the rootball had the highest daily substrate temperatures under all the shading systems. Substrate temperatures were highest under no shading or 30% shading (often >45 °C) and lowest under retractable shading (never >38 °C). Root death occurred on the southwest portion of the rootball on plants growing under all shading systems except under retractable shading. Coreopsis and Forsythia were taller when grown under 63% stationary shading compared to other shading systems but had more shoot dry weight when grown under retractable shading. Cooler substrate temperatures that prevent damage to the root system may help explain increased growth of some nursery crops when produced under retractable shading.
Pinus taeda L. seedlings inoculated with the ectomycorrhizal fungus, Pisolithus tinctorius, were grown in a glasshouse for eight months, and then subjected to rapidly developing cyclic water deficits, or to a single slowly developing water deficit. Water deficits developed at a rate of -0.16 MPa per day (predawn total water potential) for five cyclic water deficits, and at -0.04 MPa per day for the slow water deficit. In unstressed seedlings, carbon exchange rates (CER) did not differ between noninoculated and inoculated seedlings. During slow water deficit development, CER steadily declined. During rapid water deficit development, CER remained unchanged, then declined rapidly when water potentials fell below -1.3 MPa. Inoculated seedlings had higher CER when water potential was lower than -1.5 MPa.
`Pink Splash' Hyoestes were grown in chambers fitted with single-walled polycarbonate. Chambers were shaded with various photoselective shading compounds, using a white shading compound as a non-selective control. When grown under orange shading, plants had more shoot dry weight, greater leaf area, larger stem diameters, and were taller compared to plants shaded with white. When grown under green shading, plants had less shoot dry weight, less leaf area, smaller stem diameters, and were taller compared to plants shaded with white. Intermediate responses were recorded when plants were grown under red, blue or yellow shading. Differences in the ratio of red to far-red light among shading compounds did not provide a consistent explanation of growth responses.