Role of Soils in Determining Sites for Lowland Heathland Reconstruction in England

No guidelines are currently available that advise which soil properties of arable land can be used to suggest suitable locations for heathland reconstruction. This paper reviews studies comparing soil properties of heathland or semi-natural grassland with those of adjacent arable fields, investigations in the autecology of the dominant heathland plant, Calluna vulgaris (common heather), and long-term experiments of fertilizer inputs on arable soils. Three properties must be assessed before the suitability of a field can be determined: extractable phosphorus, exchangeable calcium, and pH. A number of other nutrients may also be important, but evidence is currently insufficient to substantiate this. Natural changes in levels of extractable phosphorus, exchangeable calcium, and pH appear to be very slow, so nutrient stripping and acidification will be necessary where recommended levels are exceeded to successfully restore heathland vegetation.     

Phytochrome controlled acid RNase: An “attached” protein of ribosomes

The light-dependent increment in RNase activity (which is ribosome bound in cell extracts) is distributed as a gradient increasing from base to hook of lupin hypocotyls. No evidence was found of non-specific or of specific activation of pre-formed enzyme molecules following isolation, either before or after (latent activity) destruction of particles. The autodegradation capacity of ribosomes isolated from irradiated cells was almost double that of ribosomes from etiolated tissue. It is proposed that association between the bulk of the light-controlled RNase fraction and lupin ribosomes results from binding of soluble protein. It is not clear whether binding is specific or an artifact of isolation.     

Modifications of the fertilized egg surface following the cortical reaction in Limulus polyphemus L. as viewed with the scanning electron microscope

In the development of the horseshoe crab, Limulus polyphemus, the fertilized egg undergoes a complicated cleavage (Stages 1–3) resulting in blastoderm formation (Stage 4). Stage 1 involves intralecithal cleavage and consists of nine discrete surface modifications (events) which have been briefly described with light microscopy by Brown and Barnum ('83). Since in Stage 1 the cortical reaction (events 1–4) has already been examined with ultrastructural methods, the objectives of the present study were to examine with scanning electron microscopy: (1) the first two of three intermittent granulations (events 5 and 7), and (2) the associated events characterized by smooth surfaces (events 4, 6, and 8). The first granulation occurs 2 1/2 to 3 hours after fertilization (22°C) and lasts approximately 1 1/2 hours. The second granulation appears approximately 5 hours after fertilization and lasts about 3 hours. The dynamic changes that occur during the two granulations involve the transformation of a smooth appearing embryonic surface, liberally coated with microvilli, into a granule-dominated surface on which microvilli are greatly reduced in number. Also of considerable interest are the numerous projections which begin to appear on the surface near the end of the second granulation (event 7) and dominate the surface of the following smooth step stage (event 8). Hypotheses on the significance of these dynamic changes and surface modifications involve relationships to the cell cycle, possible mechanisms for membrane storage, and secretory function.