The population genetics of Festuca rubra on park grass

An explanation for the ubiquity of sexual reproduction remains elusive although it is commonly suggested that sex and recombination facilitate a more rapid response to environmental change than clonal reproduction. If this suggestion is true then one would expect the frequency of sexual reproduction within populations to increase with rate of environmental change. The study described here investigates the potential correlation between mode of reproduction and rate of environmental change in red fescue, Festuca rubra, a clonal/sexual species of perennial grass. Populations are identified that have experienced contrasting histories of change over the past 138 years, and within which the ratios of clonally to sexually derived individuals have been determined. From these ratios the selection pressures on mode of reproduction in each of the Festuca rubra populations investigated are inferred. The unexpected discovery that Festuca rubra is represented by two sub-species at the main study site has also prompted investigations into the factors governing their relative frequencies and distributions. Since the sub-species represent different cytotypes within the red fescue aggregate, this has allowed for inferences to be made relating to their observed coexistence and the apparent overcoming of minority cytotype exclusion by the subspecies found at lower frequencies

A comparative study of phenolics in chestnut (Castanea), and their relationships with resistance to Endothia Parasitica

American chestnut (Castanea dentata Borkh.) was a highly valued forest species in the Appalachian region prior to introduction of the chestnut blight fungus (Endothia parasitica (Murr.) A. & A.), which practically eliminated it. Since no control method has been devised and oriental species and hybrids are not generally satisfactory replacements, breeding resistant individuals through selection offers some hope of reestablishment. A chemical method for screening resis-tant individuals for retention in a breeding program would be of great benefit. Since phenolic compounds have been implicated in disease resistance of some cultivated crops and forest and fruit trees, this study is an initial attempt to develop a chemical screening method by studying comparative phenolic composition of five types of inner bark samples. Inner bark of individual American chestnut trees was sampled from sound and infected stems, sound roots and debudded twigs. Sound inner bark from exotic (blight resistant) chestnut individual trees was also sampled. A stepwise extraction of air-dried bark samples was carried out in a Soxhlet apparatus using four organic solvents of increasing polarity; this resulted in twenty crude extract groups. Each extract group was investigated by one- or two-dimensional thin-layer chromatography. Phenolic compounds were located by spraying chromatograms with ferric chloride-potassium ferricyanide. Over 225 phenolic components were located. In some cases components from different samples extracted with the same solvent were indistinguishable. Some components were tentatively placed into more specific chemical classes. These compounds were found to most likely be derivatives of flavonoids, catechins, leucoanthocyanins, guaiacol and vanillin acid. A distinctive difference in chromatographic pattern was noted between American chestnut sound bark extracts and infected bark extracts from the same trees. There was almost no correlation between American chestnut root bark extracts and stem bark extracts. Little correlation was noted between American chestnut and exotic chestnut extracts; only eight components were found to be indistinguishable. Several similarities were noted between American chestnut sound stem bark and debudded twig extracts from the same trees. Individual tree data indicated considerable qualitative and quantitative variation among American chestnut trees in the extractable phenolic composition of their inner bark. A method adaptable to small quantities of extract was applied to bioassays with E. parasitica. In general, bioassay results did not correspond with observed field resistance to the chestnut blight fungus. Extracts from American chestnut infected bark extracts were most inhibitory; those from root bark of the same species least inhibitory

A Proposal for Wired City Television

This Article proposes that a national system of wired city television (WCTV), inexpensively interconnected, is the best avenue to more and more varied programs. Television would then have capacity and incentive to educate, inform, and entertain specialized interests as well as general interests and mass tastes. To put the matter as simply as possible, a system of wired city TV makes it possible to increase very greatly the number of operating channels available to almost all of the homes in the nation. The carriage of a television signal to the home from a local studio camera or tape machine then becomes far less expensive than now. Intercity connections would be accomplished as under present arrangements-microwave and cable-or could take advantage of the new satellite technology discussed by Leland Johnson. We try to show below that the great increase in availability of low-cost television channels would be a sufficient condition to insure significant increases in numbers of programs and diversity, and that other alternatives cannot accomplish this as well