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,
Wild rye (Elymus) contains several species of cool season grasses that are important components of forest and woodland ecosystems. Little specific information is known about seed dormancy in wild rye species, but cool season grasses generally display endogenous, non-deep physiological dormancy that would normally be satisfied by moist chilling during winter to permit early spring germination. However, few studies have documented the effect of extended chilling stratification on dormancy release in cool season grasses. Therefore, the objective of this study was to document the dormancy condition of representative wild rye species and to observe the impact of chilling stratification on dormancy release. Three species of wild rye (E. virginicus, E. macgregorii, and E. villosus) were selected based on their taxonomic and ecological relationships. All species showed conditional dormancy with respect to germination temperature. At 15 °C, E. virginicus, E. macgregorii, and E. villosus germinated at 75%, 81%, and 40%, respectively, compared to 5%, 3%, and 12% for each species at 20 and 25 °C. Chilling stratification at 10 °C improved germination compared to non-stratified seeds to 95% and 94% for E. m acgregorii and E. villosus, but had no effect or reduced germination in E. virginicus. Stratification at 5 °C was not as effective as 10 °C for dormancy release and appeared to cause chilling injury in E. virginicus and E. macgregorii. The data suggest that these wild rye species express a form of conditional endogenous, non-deep physiological dormancy that is most pronounced when seeds are germinated at non-optimal temperatures.
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.
Redbud (Cercis canadensis) is a small woody ornamental legume that has a hard seed coat, which imposes physical dormancy, typical of many legumes. Redbud also possesses an internal embryo dormancy that must be overcome by stratification. In order to observe the relationship between anatomy and germination, seeds were embedded in JB-4 resin during various developmental and germination stages. The seeds were cut longitudinally with a glass bladed microtome, to observe the radicle, vascular traces and testa. It appears that the vascular traces left from the funiculus serve as a weak point in non-dormant seeds that allows the radicle to rupture the testa during germination.
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).
Impatiens (Impatiens wallerana Hooker F.) and petunia (Petunia ×hybrida Hort. Vilm.) seeds were imaged using a flat-bed scanner interfaced with a personal computer programmed to capture images every hour. Images were used to measure time to radicle protrusion and seedling growth. Time to radicle protrusion was calculated as time to 50% germination or as actual germination for each seed. Seedling growth after germination was calculated from linear regression of growth over time. Radicle protrusion and seedling growth were evaluated as indicators of seed vigor. Both were good indicators of seed vigor in impatiens seed lots. These measurements of vigor were highly correlated for each impatiens seed lot and for pooled seed lots. However, there was little or no correlation between time to radicle protrusion and seedling growth on an individual seed basis. The relationship between germination speed and seedling growth rate observed in impatiens was confirmed in two petunia seed lots. This study supports the use of time to radicle emergence and seedling growth as good indicators of seed vigor. However, it appears that different aspects of seed vigor may be measured by these indicators because there was no relationship between time to radicle protrusion and seedling growth rate on an individual seed basis.
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.
Purple coneflower, Echinacea sp. (Asteraceae), is a herbaceous perennial native to North America. Within the past decade, extensive research has been conducted to confirm echinacea's immunostimulatory, antiviral, and antibacterial benefits to humans. E. angustifolia, E. purpurea, and E. pallida are the primary species grown and studied for the herbal industry. However, there are other species and cultivars that may produce higher yields in biomass and chemical quality. The objective for this study is to evaluate the differences in biomass and phenolic content of five cultivars of E. purpurea and five species of Echinacea under Kentucky growing conditions. Differences in biomass (dry weight) of Echinacea species and cultivars harvested after the first year of growth was determined. There was a significant difference in total dry weight between E. purpurea cultivars. E. purpurea `Bright Star' and `Clio' produced significantly greater total dry weight compared to all other cultivars. There was no significant difference in root or flower biomass between cultivars. Biomass production differed between Echinacea species for root, vegetative, and flower parts. The total biomass of E. purpurea and E. tennesseensis was significantly higher compared to other species. E. pallida and E. paradoxa were not significantly different from E. purpurea in root biomass, even though both species produced less above-ground growth. E. tennesseensis produced 45% to 105% more flowers compared to other species. Differences in phenolic content between species and cultivars will also be presented.
Purple Coneflower [Echinacea sp. (Asteracea)] is of great value to the horticultural, pharmaceutical, and herbal industry. More research is needed to determine cultural practices that will produce a plant high in biomass and phenolic content, the chemical used for testing the quality of the harvested plant on a percent basis of roots, flowers and vegetative parts. The objective of this experiment is to determine if biomass and phenolic content of Echinacea purpurea and E. purpurea `Magnus' is influenced by fertilization after flower bud removal and vegetative pruning. The second objective of this study is to form an evaluation of the differences in biomass and phenolic content of five cultivars of E. purpurea and five species of Echinacea. Biomass and phenolic content will be evaluated to determine if exposing these plants to various treatments increases the quality of the plant over 1 and 2 years of growth. Differences in dry weights of Echinacea species and cultivars harvested after the first year of growth was determined. There was a significant difference in total dry weight between E. purpurea cultivars. Echinacea purpurea `Bright Star' and `Clio' significantly produced the most total dry weight compared to all other cultivars. There was no significant difference in root or flower biomass between cultivars. Biomass of Echinacea species was significantly different in root, vegetaive and flower parts. The total biomass of E. purpurea and E. tennesseensis was significantly higher compared to other species. Echinacea pallida and E. paradoxa were not significantly different from E. purpurea in root biomass, even though both species were small in above ground growth. Echinacea tennesseensis significantly produced 45% to 105% more flowers compared to other species. Differences in phenolic content between species and cultivars will also be presented.