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- Author or Editor: Robert L. Geneve x
An interactive multimedia presentation was developed using authoring software (Authorware from Macromedia) to provide information on plant anatomy and cell biology. Our current course in growth and development of horticultural crops has limited time and lab facilities available for these subjects, yet a good foundation in this area is important to understanding growth and development. This software uses a variety of techniques, including color digital images, illustrations, cartoon animation, and video, to teach aspects of cell biology and different plant cell types. In addition, a review session allows students to interactively test their knowledge of the subject. The software was placed on a Dept. of Horticulture server that provided student access to a folder for course work. Students were able to access the software from anywhere on campus via the University network. Multiple students can use the software simultaneously. The approach of using a local server provided easy access and avoided some of the delays involved with viewing large (1 mb) images found when using the World Wide Web. It took students several weeks to complete the software's modules. Then, students completed an independent plant anatomy lab using the software for reference. Students were required to create a virtual notebook of labeled digital images captured from prepared microscope slides using a microscope attached with a digital camera and linked to a computer. Students found this approach to learning to be challenging, and initial feedback has been very positive.
Adventitious root formation in debladed petiole cuttings of English ivy proceeds via a direct rooting pattern for the easy-to-roof juvenile phase, while the difficult-to-root mature phase roots through the indirect pattern, Juvenile petiole cuttings treated with NAA (100 μM) plus the polyamine biosynthesis inhibitor, DFMA (1 mM), formed an increased number of roots per cutting initiated through the indirect rooting pattern. The increased formation and the change in rooting pattern were reversed by the addition of putrescine (1 mM). Delaying auxin application to petiole cuttings for 15 days, also induced juvenile petioles to root by the indirect pattern. This could be reversed by rebounding the base of the cutting prior to auxin application at day 15. The data support the use of the terms “pre-competent root forming cells” (PCRFC) and `induced competent root forming cells' (ICRFC) to describe the target cells for the initial events of root formation for the direct and indirect patterns, respectively,
Seed dormancy in Eastern redbud (Cercis canadensis var. canadensis L.) can be overcome by seedcoat scarification to allow water imbibition, followed by chilling stratification to permit germination. During chilling stratification, there was an increase in the growth potential of the embryo as indicated by the ability of the isolated embryo to germinate in osmotic solutions. Penetration resistance of the testa also decreased after chilling stratification. The combination of seedcoat alteration and the increase in embryonic growth potential was associated with overcoming dormancy in redbud seed. GA3 or ethephon (50 μm) stimulated germination (28% and 60%, respectively) and increased the growth potential of treated embryos. Chemical names used: gibberellic acid (GA3), (2-chloroethyl) phosphoric acid (ethephon).
Different planting dates, plant densities and pinching practices were used to determine the production practices that produced the best quality cut stems from field grown godetia under Kentucky conditions. Godetia `Grace Salmon' transplants were planted at a plant density of 40 plants m-2 on Mar 23, Apr 8 and Apr 23, 1991 in ground beds with black plastic mulch. All plants flowered in early to mid June, but plants from the Mar 23 planting date had the highest yields of commercial quality stems (387 stems m-2) and over 80% of the stems were longer than 55 cm. In a separate experiment, transplants of `Grace Red' and `Grace Rose Pink' were planted on April 5 at plant densities of 4.5 m-2 (unpinched), 10 m-2 (soft pinch on May 1) and 23 m-2 (hard pinch on May 1). Pinching treatments were used to increase the number of secondary and tertiary branches on each plant. Although the pinching treatments produced more branches, a low percentage of the branches were commercial quality cut stems.
Early seedling growth rate can be used to estimate seed vigor for small-seeded vegetable and flower seeds. However, hand measurement of small seedlings is tedious and difficult to reproduce among analysts. Computer-aided analysis digital images of seedlings should improve accuracy and reproducibility. A flat-bed scanner fitted with base and top lighting provided high resolution images of even small-seeded species like petunia [Petunia ×hybrida `Blue Picotee' (Hort) Vilm.] and lisianthus [Eustoma grandiflorum `Mariachi Pure White' (Raf.) Shinn]. Uniform lighting was provided and images were captured and analyzed in less than 2 minutes. A clear, cellulose film was used as the germination substrate in petri dish germination assays to facilitate capturing images with a flat-bed scanner. The transparent medium permitted seedlings to be imaged without removal from the petri dish and also allowed for repeated measures of the same seedlings in order to calculate growth rate. Six species evaluated in this study included cauliflower (Brassica oleracea L., var. Botrytis), tomato (Lycopersicon esculentum Mill. `New Yorker'), pepper (Capsicum annuum L. `North Star'), impatiens [Impatiens walleriana Hook. f. `Impact Lavender'], vinca [Catharanthus roseus (L.) G. Don. `Little Bright Eye'], and marigold (Tagetes patula L. `Little Devil Flame'). For germination and early seedling growth, the cellulose film compared favorably with other standard germination media (blue blotter and germination paper) for five of the six species tested. Computer analysis of seedling length was possible for all six species and was statistically similar to hand measurements averaged for three analysts.
Somatic embryos from Eastern redbud show a high degree of malformation during development and a low conversion rate to seedlings. This problem is common with somatic embryo systems, especially with legume species. A procedure for multiple shoot formation from somatic embryo explants of Eastern redbud was developed that bypasses the need for germination to recover plantlets. Somatic embryo explants cultured on DKW medium containing benzyladenine (BA) and thidiazuron (TDZ) produced more shoots than either treatment alone. The highest number of shoots (3.3 to 3.4 shoots per explant) was obtained from partially desiccated and wounded explants treated with a combination of 5 or 10 M BA and 0.5 or 1.0 M TDZ for 20 days before being transferred to the same medium without TDZ. The number of shoots formed was increased from 1.5 to 3.2 shoots per explant by cutting through the cotyledonary node prior to culture. In addition, the frequency of explants forming shoots was increased by desiccation of somatic embryo explants to ≈50% moisture and by using somatic embryos with two well-formed cotyledons as explants.
The seedcoat anatomy in the hilar region was examined in dry, imbibed and germinating seeds of Eastern redbud (Cercis canadensis L.). A discontinuous area was observed between macrosclereid cells in the palisade layer of the seedcoat which formed a hilar slit. A cap was formed during germination as the seedcoat separated along the hilar slit and was hinged by the macrosclereids in the area of the seedcoat opposite to the hilar slit. The discontinuity observed in the palisade layer was the remnant of the area traversed by the vascular trace between the funiculus and the seedcoat of the developing ovule. There were no apparent anatomical differences in the hilar region of the seedcoat between dormant and nondormant imbibed seeds. However, the thickened mesophyll of the seedcoat in this region and the capacity of the endosperm to stretch along with the elongating radicle may contribute to maintaining dormancy in redbud seeds.
Adventitious shoot induction was studied using isolated parts of in vitro grown seedlings of Eastern redbud. The explants studied included the cotyledon node (with or without cotyledons), cotyledon, hypocotyl, epicotyl, root, nodal stem and seedling leaf pieces. Explants were treated with a factorial combination of benzylaminopurine (BAP) and thidiazuron (TDZ) on DKW medium. Cultures of Eastern redbud produced a low frequency of adventitious shoot formation for all explants tested except for explants with the cotyledonary node. These explants produced 5.9 shoots per culture after treatment with 10μM BAP + 1μM TDZ. However, shoots produced on a medium containing TDZ failed to elongate. Many of the TDZ induced shoots were abnormal and distorted. Shoot elongation was promoted by transferring explants to a medium with BAP alone.