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Robert L. Geneve and Charles W. Heuser

Abstract

Ethylene liberated from control and auxin-treated cuttings of Vigna radiata (L.) R. Wilcz cv. Berken was monitored for 14 hours. For root initiation, naphthaleneacetic acid (NAA) and indolebutyric acid (IBA) were the most effective with indoleacetic acid (IAA) intermediate and 2,4-dichlorophenoxyacetic (2,4-D) the least effective. No correlation was observed between the quantity of auxin-induced ethylene evolved and the number of roots formed. Decreasing the NAA solution pH from 7.0 to 3.0 reduced the evolution of ethylene but did not alter the rooting response of the cuttings. It was concluded that stimulation of adventitious root initiation by auxin is not mediated by ethylene.

Open access

Robert L. Geneve, Wesley P. Hackett, and Bert T. Swanson

Abstract

An in vitro system has been developed to study adventitious root initiation in the juvenile and mature phases of English ivy (Hedera helix L.). The system uses de-bladed petiole explants cultured in a defined liquid medium. Adventitious roots are visible macroscopically after 18 days. Juvenile petiole explants show a dose-response to auxin application with optimal root initiation at 100 μM NAA or IAA. With optimal auxin concentration, root initials form in juvenile petiole explants directly from cortical parenchyma cells, which involves induction (1–6 days), meristem organization (6–9 days), and root elongation stages (9–18 days). Sucrose is required for outgrowth of root primordia but not for initiation of primordia. Mature petiole explants respond to auxin with random cell divisions in cortical parenchyma cells; root initials form at a low frequency from callus resulting from this cortical cell division. Distribution of 14C at various times after administration of 14C-labeled NAA is similar in juvenile and mature petioles. Because of their difference in rooting potential, coupled with similarity in anatomical organization, distribution of 14C from NAA, and identical genotype, juvenile and mature petioles provide an excellent experimental system for analyzing the morphogenetic, physiological, and genetic basis of rooting potential. Chemical names used: 1-napthaleneacetic acid (NAA); 1H-indoIe-3-acetic acid (IAA).

Open access

Robert L. Geneve and Charles W. Heuser

Abstract

Adventitious root initiation decreased in ‘Berken’ mung bean cuttings treated with ≥ 10−4 m (2-chloroethyl) phosphonic acid (ethephon). Ethephon at 10−3 but not 10−5 m reduced root length and caused a redistribution of roots along the hypocotyl. The application of ethephon in combination with indoleacetic acid (IAA), indolebutyric acid (IBA), naphthaleneacetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D) reduced root initiation. An initial treatment of ethephon followed by NAA, or NAA followed by ethephon, inhibited root initiation to the same degree. Ethephon—whether applied at the time of cutting preparation or up to 12 hours later—inhibited root initiation to the same extent.

Full access

Servet Caliskan, Sharon T. Kester, and Robert L. Geneve

A laboratory exercise is presented that demonstrates the impact of seed coverings and hormones on seed dormancy and release in seeds with endogenous, physiological dormancy. The materials and methods are simple and inexpensive and can be accomplished as an on-campus laboratory or as a distance education exercise. The execution of the laboratory is rapid (≈1 hour), and the results are obtained in 2 weeks. The exercise generates an opportunity for the discussion of a complex subject that involves the interaction of two tissue types within the seed (the embryo vs. the seed coverings) and nicely illustrates their role in seed dormancy maintenance.

Free access

Sandra B. Wilson, Robert L. Geneve, and Fred T. Davies

Interactive web-based questions were developed for students to review subject matter learned in an online plant propagation course. Articulate Storyline software was used to build nearly 250 review questions with five different testing styles to ascertain proficiency in subject areas, including the biology of propagation, the propagation environment, seed propagation, vegetative propagation, micropropagation, and cell culture. Questions were arranged to correspond to the supporting textbook chapters in Hartmann and Kester’s Plant propagation: Principles and practices, ninth edition. These are open access and available to instructors and students worldwide. Users received immediate feedback for each question answered correctly or incorrectly. The system remembers where one leaves off, which enables starting and stopping multiple times within a chapter. Means of pre- and posttest responses to nine content knowledge items showed that students perceived a significant content knowledge gain in the course. These online interactive reviews can be adapted easily to other courses in a variety of fields, including horticulture, botany, systematics, and biology. They can also be expanded to overlay multiple objects and trigger events based on user response. Since inception, the website hosting these online reviews averaged 156 unique visitors per month. Students have reported this to be a useful tool to prepare them for course exams.

Free access

Liliek S. Utami, Robert L. Geneve, Robert G. Anderson, and Sharon T. Kester

Satin flower (Clarkia amoena ssp. whitneyi - syn. Godetia) is a cool season native to the Western U.S. being studied for its potential use as a cutflower crop in Kentucky. In May 1989, plants of `Grace Salmon' were transplanted to the field into black fabric mulch. A factorial experiment was conducted with three pinching treatment (no pinch, pinched early at the third mode prior to transplanting, and pinched in the field at the third mode after the first flower bud was visible) and at three spacings (15, 30 end 45 cm). There were significant main and interaction effects for both pinching and spacing for the number of flowering stems, stem length and plant diameter. However, no treatment combination consistently produced flowering stems of sufficient length for commercial quality. This may be due to the later spring planting date and hot weather in 1989. In an attempt to increase flower stem length, Godetia `Grace Salmon' plants have bean transplanted on April 10, 25 and May 10, Plants will be pinched in the greenhouse or grown without pinching et 45 or 15 cm spacing, respectively, The. effect of supplemental lighting and long days during transplant production will also be considered,

Free access

Victoria M. Anderson, Douglas D. Archbold, Robert L. Geneve, Dewayne L. Ingram, and Krista L. Jacobsen

Organic and low-input production systems are increasingly of interest in medicinal plant production, such as Calendula officinalis, a medicinal plant grown for essential oils. However, in these systems the effects of nutrient availability and water stress may act singularly or in combination to affect plant growth and medicinal compound production. This study investigated the effects of organic and conventional fertility sources and drought stress effects on four calendula cultivars. Soil nitrogen (N) status, plant growth, productivity, and essential oil quality and quantity were measured. The plant growth response to increased N availability varied by cultivar, indicating that some cultivars may be better suited to low-input fertility regimes. Fertility source did not significantly affect essential oil quality or quantity. Drought stress reduced plant growth but increased the quality of essential oil, as indicated by the concentrations of specific constituents, although it did not reduce total oil yield. These results indicate that organic and low-input farming systems may significantly reduce plant growth, but may not necessarily affect essential oil yield or quality. As such, the sustainability of medicinal plant production systems may be improved by reductions in water and conventional fertilizers without significant reductions in medicinal compound production.

Free access

Susmitha Nambuthiri, Amy Fulcher, Andrew K. Koeser, Robert Geneve, and Genhua Niu

Market researchers have found that nursery and greenhouse production practices that reduce plastic use can increase consumer interest. However, there are broader crop performance, production efficiency, and environmental factors that must be considered before adopting containers made with alternative materials. This review highlights current commercially available alternative containers and parent materials. In addition, findings from recent and ongoing nursery, greenhouse, and landscape trials are synthesized, identifying common themes, inconsistencies, research gaps, and future research needs.

Free access

Tera M. Bonney, Shawn P. Brown, Snake C. Jones, Kirk W. Pomper, and Robert L. Geneve

The pawpaw [Asimina triloba (L.) Dunal] is a native plant found mainly in the southeastern and eastern United States, and its fruit has great potential as a new high-value crop in these regions. Although there are ≈45 named pawpaw cultivars, breeding for improvement of specific traits, such as fruit size and quality, is desirable. Our long-term goal is to utilize molecular marker systems to identify markers that can be used for germplasm diversity analyses and for the construction of a molecular genetic map, where markers are correlated with desirable pawpaw traits. The objective of this study was to identify random amplified polymorphic DNA (RAPD) markers that segregate in a simple Mendelian fashion in a controlled A. triloba cross. DNA was extracted from young leaves collected from field-planted parents and 20 progeny of the cross 1-7 × 2-54. The DNA extraction method used gave acceptable yields of ≈7 μg·g-1 of leaf tissue. Additionally, sample 260/280 ratios were ≈1.4, which indicated that the DNA was of high enough purity to be subjected to the RAPD methodology. Screening of 10-base oligonucleotide RAPD primers with template DNA from the parents and progeny of the cross has begun. We have identified two markers using Operon primer B-07 at 1.1 and 0.9 kb that segregate in a simple Mendelian fashion in progeny of the 1-7 × 2-54 cross. Other primers and controlled crosses will also be screened.

Free access

Erin G. Wilkerson, Richard S. Gates, Sérgio Zolnier, Sharon T. Kester, and Robert L. Geneve

Rooting stage, transpiration capacity, and relative water content were measured in cuttings every 5 days for 25 days. Cell divisions in phloem parenchyma were evident between 5 and 10 days after sticking, organized subcuticular root primordia were present between 10 and 12 days, and roots emerged between 12 and 15 days. Transpiration was measured in poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch `Freedom Dark Red') cuttings under light or dark conditions at increasing vapor pressure deficit (VPDair) levels during different stages of rooting. Transpiration capacity did not increase until roots emerged on the cuttings. Light had a significant impact on transpiration rates only after roots emerged. Light was more significant than VPDair for determining actual transpiration. Between visible rooting (15 days) and 25 days, increase in total root length was linear (r 2 = 0.92) and significantly correlated with transpiration (r 2 = 0.98). Transpiration capacity increased after visible rooting, but did not significantly increase under non-misted conditions until cuttings were well-rooted and had a total root length >50 cm (18 days after sticking). Relative water content measured before and after entering the transpiration chamber confirmed that cuttings were only able to take enough water from the medium to continue sustained transpiration after 18 days. A cutting coefficient was developed from transpiration data to modify the misting interval for dynamic controlled misting. Greenhouse studies showed a 55% or greater reduction in water use with dynamic control compared to constant static or stepped down static control. Rooting performance was unaffected by misting interval. Foliar nutrition was significantly reduced in all cuttings after 7 days in the mist bench, but changes in foliar elemental content were not correlated with misting interval.