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- Author or Editor: James Affolter x
Horticultural science has an essential role to play in the conservation of rare plants, but to date, most horticultural research in this field has taken place on an informal rather than experimental basis. Plant conservation as a scientific and practical discipline would benefit greatly from applying the more rigorous approach characteristic of commodity-oriented horticultural research. In turn, the profession of horticultural science has a great deal to gain by participating more actively in plant conservation programs. Benefits include an influx of new ideas, new people, and new resources. Some of the traditional research fields within horticulture that are directly relevant to rare plant conservation include: seed technology, propagation and tissue culture, nutrition, growth regulation, soil management, and protection from pests and diseases. Three case studies illustrate various ways in which the theory, technology, and knowledge base of horticulture can be applied to plant conservation. They include the rare plant propagation program at Bok Tower Gardens, Lake Wales, Fla.; mountain meadow revegetation projects in Mount Rainier and Olympic National Parks in Washington; and research activities of the recently established Georgia Plant Conservation Alliance.
The province of Cordoba in central Argentina is naturally rich in aromatic and medicinal herbs that are in high demand as ingredients in teas and herbal medicines. Most of the herbs sold are harvested from natural populations, and this activity is a primary source of income for families in the Sierra de Cordoba region. As a result of over-collection and other poor harvesting practices, many native plant populations have been reduced in size or extirpated. The economic consequence of the gradual decline of this resource has been a loss of real income in rural areas coupled with a pattern of emigration from small towns to larger cities. PRODEMA is a collaborative effort by universities in Argentina and the United States, with the sponsorship of the Cordoba government, to domesticate and to market the most commercially important species. Horticultural research has focused on the development of propagation techniques and identification and selection of desirable chemotypes.
Georgia plume (Elliottia racemosa, Ericaceae) is a threatened, woody plant endemic to Georgia's Coastal Plain region in the southeastern United States. Populations of the plant have a fragmented distribution within a restricted range and are characterized by low genetic diversity and a lack of sexual recruitment. Georgia plume cannot be effectively propagated using conventional methods. We have developed an in vitro shoot regeneration system that is effective with explants obtained from mature plants in the wild. The objective of this study was to determine the efficacy of using this in vitro protocol to regenerate proliferating shoot cultures from 34 georgia plume genotypes obtained from divergent populations. Young expanding leaves were cultured on Gamborg's media supplemented with 10 μM thidiazuron and 5 μM indole-3-acetic acid. After 8 weeks, tissues were transferred to a shoot elongation medium with 25 μM 2-isopentenyl adenine. Of the 34 genotypes tested, 91% formed shoot primordia and 85% regenerated shoots within 6 months of inoculation. This study verifies that tissue culture can be used to produce adventitious shoots from a wide range of georgia plume genotypes. Within a coordinated conservation program, tissue culture is a feasible system to use for safeguarding and reintroduction of genetically diverse plant material, which may be critical to the survival of this rare species.
The use of medicinal plants in the United States is increasing. Holy basil (Ocimum tenuiflorum L. and Ocimum gratissimum L.), a medicinal herb native to India, has become increasingly popular for its therapeutic benefits. Traditionally, holy basil has been used to promote longevity by reducing stress and restoring balance to the body. Because it is easy to grow and adapts to a wide range of growing conditions, there is great potential for holy basil production in the southeastern United States. The purpose of this study was to evaluate holy basil varieties for harvestable weight and essential oil content. Fourteen varieties of holy basil were grown during the 2015 and 2016 seasons and compared. The main active compound in the holy basil essential oil fraction, eugenol, was quantitated and compared for each variety, because it is believed to be responsible for many of the health-promoting effects. Overall, there were significant differences in harvestable weights and essential oil yields among the varieties, and a significant effect of growing season. The eugenol content was highly variable among the varieties examined, with higher eugenol contents in 2016 than in 2015. The variety that had the overall highest yield, essential oil content, and eugenol concentration was PI 288779, a USDA accession, suggesting its use in future breeding research.
Georgia plume (Elliottia racemosa) is a threatened woody plant endemic to the Coastal Plain region of Georgia in the southeastern United States. Seed set is low in most populations, and sexual recruitment has not been observed in recent times. The objective of this study was to describe the floral biology of georgia plume. which is fundamental information needed to develop an understanding of the causes for lack of sexual reproduction in natural populations. Floral development was characterized and morphological characteristics at key developmental stages ranging from small, unopened buds to open flowers with receptive stigmas were examined using light and scanning electron microscopy. Flowering is protandrous, and anthers dehisce releasing pollen within closed buds before stigmas are receptive. Pollen tetrads, aggregated by viscin strands, are presented on unreceptive stigmas when petals reflex. Receptive stigmas developed a raised and lobed central region with a clefted opening leading to a stylar canal containing exudate produced in secretory regions. Receptivity of the non-papillate stigma is indicated by the formation of an exudate droplet, which is formed within 1 day after flower opening. Pollen viability was low to moderate; tetrad germination ranged from 20% to 40% using in vitro germination assays indicating poor pollen quality and may contribute to lack of seed development in some populations. No developmental abnormalities in stigmas or styles were observed indicating other factors are responsible for lack of sexual recruitment in the wild.
Lysimachia congestiflora Wils. (Primulaceae) is a new crop for American nurseries and may be used as an annual in the north and a half-hardy perennial in the south. The purpose of this study was to investigate the influence of photoperiod, temperature, and irradiance on its flowering and growth. Three experiments were conducted with photoperiod of 8, 12, 16 hrs day-1, temperature of 10, 18, 26C, and irradiance of 100, 200, 300 μmol m-2s-1, respectively. Plant.9 given long day photoperiod (16 hours) flowered 21 and 34 days earlier, respectively, than plants at 12 sad 8 hour photoperiods. Plants under long day treatment produced more flowers than those at 8 and 12 hours. Plant dry weight did not differ between treatments, but plants grown in the long day treatment produced fewer but larger leaves. Total plant growth increased as temperature increased, but lower temperature (10C) decreased flower initiation and prevented flower development, while high temperature (26C) reduced the longevity of the open flowers. Flowering was accelerated and dry weight increased as plants were subjected to high irradiance levels. The results suggest that Lysimachia congestiflora is a quantitative long day plant. It should be grown under a photoperiod of at least 12 hours at a temperature of approximately 20C. Low light areas should be avoided and supplemental lighting to provide the long days may improve the plant quality.
Many bromeliad species indigenous to the rain forests of Central and South America are threatened because of over-collection and habitat destruction. Studies were conducted to develop propagation protocols for Tillandsia eizii, a rare ornamental bromeliad of ceremonial significance to the Highland Maya communities in Chiapas, Mexico. We anticipate using in vitro propagation for the conservation of this species with the potential of utilizing bromeliads as an alternative and sustainable forest resource. Protocols were developed for the sterilization and germination of axenic seed. Seedling growth in vitro was assessed and outplanting studies were conducted. Media were evaluated to promote adventitious bud production in experiments using the plant growth regulators naphthaleneacetic acid and benzylaminopurine. Pulse time and duration, as well as the stage of seed development, had a marked effect on bud production. The effects of various potting media on plant growth and survival were assessed. A pure pine bark medium elicited over 95 percent survival. Plants exhibited a “tank-like” morphology characteristic of plants in the wild.
Tillandsia eizii is an epiphytic bromeliad that due to over-collection, habitat destruction, and physiological constraints has declined to near threatened status. This species exhibits high mortality in the wild, and seed are characterized by low percentages of germination. As a means to conserve this species, in vitro culture protocols were developed to enhance seed germination and seedling growth. A sterilization protocol using 70% ethanol for 2 minutes followed by 2.6% NaOCl for 40 minutes disinfested seed and promoted seedling growth. Sucrose incorporated into the culture medium had no effect on germination or growth, while NAA inhibited growth, but not germination. Cultures maintained under a 16-hour photoperiod at 22 °C exhibited greater growth than those grown at 30 °C. Seed that germinated in the dark remained etiolated and failed to develop even after transfer to light conditions. Plants grown in vitro were successfully acclimatized and transferred to the greenhouse. Over 86% survival and rapid growth were obtained with either an all-pine-bark medium, or a mixture of 2 redwood bark: 2 fir bark: 2 potting mix: 1 perlite. This demonstrated that in vitro culture of seed may be used to rapidly produce large numbers of T. eizii, and thus can be used for the conservation and reintroduction of this species.