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Bipul K. Biswas*, Nirmal Joshee, and Anand K. Yadav

Guava (Psidium guajava L.), also called `apple of tropics,' is immensely nutraceutical and horticulturally important. Being a tropical plant, it cannot stand temperatures below 25° F and needs frost protection to grow in temperate regions. To adapt in cold climate, cold hardy guava cultivars are needed. Conventional ways are uneconomic in time and efforts. Still, transgenic plants developed using biotechnological approaches of tissue culture and rDNA technology, appear to have great potential. Thus, protocols for in vitro propagation of guava were developed via organogenesis and somatic embryogenesis using nodal explants from mature trees and young zygotic embryos, respectively. Nodal explants induced multiple shoots when cultured on MS medium fortified with KIN, BAP and Ad.S. Adding a (NO3)2 to medium was useful to prevent in vitro shoot tip browning of adventitious shoots. Rocker liquid culture greatly increased growth of multiple shoots compared to the agar-based medium. It appears to be a good tool for woody plant tissue culture. Induction of somatic embryos in guava was also achieved on MS medium supplemented with IAA auxin. About 80% to 90% somatic embryos germinated normally. To achieve Agro-bacterium-mediated gene transfer in guava, on-going co-cultivation of organogenic tissues of guava is to optimize protocols for freeze tolerance gene (CBF1, CBF2, CBF3) transfer. Plasmid vectors containing selectable markers (nptII gene for antibiotic selection and GUS reporter gene as scorable gene mediated selection), with CaMV 35S promoter gene has been introduced into guava tissues and the resultant plants showed antibiotic resistance. Details of the experimental procedures and up-to-date results will be discussed.

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F.J. Lawrence, G.J. Galletta, and D.H. Scott

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Douglas C. Sanders

The diversity of site-specific management opportunities is demonstrated by the list of topics and speakers we have in the colloquium. These techniques will help use to better understand, adapt, and adjust horticultural management to the benefit of producers, researchers, and the consumer. With these technologies we will be able to reduce costs, environmental impacts, and improve production, and quality. Horticulture will use more both remote and manually operated devices that allow more intensive planning and management of our production systems. This colloquium has just scratched the surface of the potential of these techniques in horticulture. We hope that the sampling will whet your appetite for great depth of study of the opportunities that are just around the corner.

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Lee S. Altier, R. Richard Lowrance, and R.G. Williams

Even with careful management, within-field practices are often insufficient to prevent considerable nonpoint source pollution to adjacent streams. Water resources suffer from sediment, N, and P transported in surface runoff and N in subsurface movement when fields are cultivated up to stream banks. The maintainance of forested buffer systems between farmland and streams has been proposed as a remedy for mitigating pollution. Chemical movement through such a buffer system has been monitored for several years at the University of Georgia Coastal Plain Experiment Station. With the aid of that data, the Riparian Ecosystem Management Model is being developed to simulate biological, chemical, and hydrologic processes in order to evaluate the effectiveness of buffer system management for reducing the influx of pollutants to streams. The model allows an examination of the long-term potential of a buffer system under changing environmental conditions.

Open access

M. N. Westwood

Abstract

Of the 90 plant collections listed by Wyman (The arboretums and botanical gardens of North America, Chronica Botanica X: 395-497, 1947) 54 indicated their chief function as either education, research, or both. These terms have different meanings to different people but either function could best be carried out if the collected species were authentic and correctly labelled.

Open access

Robert C. de Wilde

Abstract

In 1946 Kabachnik and Rossiiskaya (96) reported the chemical synthesis of “2-chloroethanephosphonic” acid and in 1963 Maynard and Swan (125) described the formation of ethylene from this compound. When (2-chloroethyl)phosphonic acid (ethephon; also variously cited as 2-chloroethanephosphonic acid, Amchem 66-329, CEPA and Ethrel® disintegrates, it releases ethylene and also chloride and phosphate ions (43, 67, 125, 196, 202) Ethephon is essentially stable in aqueous solutions below pH 4. When the presence of hydroxyl ions is increased and the pH rises above 4, disintegration of the chemical takes place. The pH of the cytoplasm of plant cells is generally greater than 4, so the plant growth activity of ethephon has been attributed primarily to its ability to release ethylene to plant tissues (14, 43, 132, 195, 196). Ethrel formulations provide a convenient way to apply ethylene without the need of gas-confining chambers.