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Sullivan Lynch, Rachel K. Johnston, Ron O. Determann, Jennifer M. Cruse-Sanders and Gerald S. Pullman

estimated to have the greatest number (2553) of endangered and threatened species ( Pence, 2010 ). Successful seed cryopreservation using direct immersion or slow cooling followed by rapid thawing has been demonstrated for several commercial and endangered

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Paula M. Pijut and Melanie J. Moore

Juglans cinerea L. (butternut) is a hardwood species valued for its wood and edible nuts. Information on the vegetative propagation of this species is currently unavailable. Our objective was to determine the conditions necessary for successful stem-cutting propagation of butternut. In 1999 and 2000, 10 trees (each year) were randomly selected from a 5- and 6-year-old butternut plantation located in Rosemount, Minn. Hardwood stem cuttings were collected in March, April, and May. Softwood cuttings were collected in June and July. K-IBA at 0, 29, or 62 mm in water and IBA at 0, 34, or 74 mm in 70% ethanol were tested for root induction on cuttings. The basal end of cuttings were dipped in a treatment solution for 10 to 15 seconds, potted in a peat: perlite mixture, and placed in a mist bed for 5 to 8 weeks. Rooted cuttings were gradually hardened off from the mist bed, allowed to initiate new growth, over-wintered in a controlled cold-storage environment, and then outplanted to the field. For hardwood cuttings, rooting was greatest for those taken in mid-May (branches flushed out), 22% with 62 mm K-IBA and 28% with 74 mm IBA. Softwood cuttings rooted best when taken in June (current season's first flush of new growth or softwood growth 40 cm or greater) and treated with 62 mm K-IBA (77%) or 74 mm IBA (88%). For 1999, 31 out of 51 rooted softwood cuttings (60.8%) survived overwintering in cold storage and acclimatization to the field. For 2000, 173 out of 186 rooted softwood cuttings (93%) survived overwintering and acclimatization to the field. Chemical names used: indole-3-butyric acid-potassium salt (K-IBA); indole-3-butyric acid (IBA).

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Martín Mata-Rosas, Rosario Julieta Baltazar-García and Victor Manuel Chávez-Avila

threatened species ( Jiménez et al., 1998 ; SEMARNAT, 2002 ). Tissue culture techniques have been used to propagate and conserve endangered orchid species ( Sarasan et al., 2006 ) and reports of such research with native Mexican orchid species are becoming

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Justin A. Porter, Hazel Y. Wetzstein, David Berle, Phillip A. Wadl and Robert N. Trigiano

Georgia plume ( Elliottia racemosa , Ericaceae) is a beautiful, rare, small tree endemic only to Georgia, where it is listed as a threatened species ( Georgia Department of Natural Resources, 2006 ). It produces spectacular plume-like white

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Seong Min Woo and Hazel Y. Wetzstein

Georgia plume has not been previously reported and may be a method for the conservation and propagation of this threatened species. The overall goal of this study was to develop tissue culture protocols for the mass propagation of Elliottia racemosa

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Seong Min Woo and Hazel Y. Wetzstein

Georgia plume (Elliottia racemosa Muhlenb. ex. Elliott) is a rare deciduous shrub or small tree. It has sustained severe loss of habitat and its range is now restricted to a limited number of sites in the state of Georgia. Tissue culture protocols have been developed as a means to propagate and conserve this threatened species using leaf explants induced on medium supplemented with 10 μm thidiazuron (TDZ) and 5 μm indole-3-acetic acid (IAA). Bud-like clusters, elongated embryo-like protrusions, and shoot-like structures were produced from the leaf explants. Morphological and histological evaluations of cultures during induction and development were conducted using light microscopy of sectioned material and scanning electron micrography. Histology of explant tissues indicates that plant regeneration of Georgia plume occurs through a shoot organogenesis pathway that involves the formation of actively dividing meristematic regions originating in subepidermal cell layers that proliferate to form protuberances on the explant surface. Numerous well-formed shoot apical meristems with leaf primordia are produced, as well as fused shoot-like structures. Elongated, embryo-like structures had various degrees of shoot apex development. Evaluations of serial sections found that they lacked a defined root apex, and that basal portions were composed of parenchymatous files of cells with a broad point of attachment to the parent tissue. The lack of bipolarity and a root pole signifies that true somatic embryogenesis does not occur.

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Margaret R. Pooler, Ruth L. Dix and Joan Feely

The issue of invasive plants has become a concern to a variety of groups, including environmentalists, policymakers, and nurserymen. Although many surveys of invasive plants have been made, little research on the biology of hybridization has been conducted. Bittersweet (Celastrus) species serve as a good model system to test the effects of interspecific hybridizations since native and introduced species are found in the U.S. The American bittersweet (Celastrus scandens L.) is a deciduous climbing or twining shrub native to eastern and central North America. Although the bark has been used for medicinal purposes, the plant is cultivated as a nursery crop primarily for its bright red berries. In its natural habitat, native bittersweet is also an important source of food and cover for wildlife. Over the past several decades, populations of native bittersweet have declined to such low levels that some states are considering listing it as a threatened species. One reason for the rarity of American bittersweet in the wild is thought to be competition and possibly hybridization with an aggressive introduced species, oriental bittersweet (Celastrus orbiculatus Thunb.), which was introduced from Asia into the U.S. in 1860 as an ornamental. This plant can form dense, tangled, impenetrable thickets or climb small trees to girdle and smother them. It has been seen in at least 21 states since it was first recorded as an escape plant in 1912. Our objective was to determine whether oriental bittersweet can hybridize with native bittersweet, thus contributing to the loss of native populations in the United States. We performed controlled pollinations using C. scandens as the female parent and C. scandens or C. orbiculatus as the male parent. Although the intraspecific pollinations resulted in significantly more germinating seedlings than the interspecific crosses, the seedlings from the interspecific crosses had less seed dormancy and were more vigorous and more quick to vine than the intraspecific seedlings. These results indicate that the decline of the American bittersweet may be due to interspecific hybridizations with the invasive introduced species.

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Thomas E. Marler

, horticulturists would collaborate with the conservation and restoration community to identify pertinent applications for their contributions. My interest in how horticultural research can contribute to conservation of threatened species evolved because of

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Andrea N. Brennan, Valerie C. Pence, Matthew D. Taylor, Brian W. Trader and Murphy Westwood

cryopreservation, another potential conservation method for oaks ( Xia et al., 2014 ). Oak tissue culture research has predominantly focused on a handful of economically important, rather than threatened, species. These include english oak [ Quercus robur