INTERACTIONS OF 1-METHYLADENINE AND THE SURFACE OF STARFISH OOCYTE

Three metabolic inhibitors, mycostatin, concanavalin A (Con A) and cytochalasin B (CB) were used to study the interactions between l-methyladenine (1-MA) and the starfish oocyte surface leading to germinal vesicle breakdown (GVB). Mycostatin and Con A had no obvious effects on GVB. CB did not inhibit, but did delay GVB. This delaying effect was interpreted as having multiple 1-MA reactive "sites" on the surface. The results also suggested that not all of them were needed to react with 1-MA to bring about GVB.     

Lipid Metabolism in Dehydrating Peanut Kernels

Metabolism of radioactive lipids in kernels from peant plants subjected to ¹⁴C₂ under field conditions was studied during dehydration (curing) of the seeds at 22°C or 50°C. Synthesis of lipid was predominant during the first 6 to 12 hours of dehydration whereas degradation dominated between 12 to 24 hours of curing. These changes were related to the moisture content of the dehydrating kernels; a moisture range of 42 to 47% was found to be an important factor influencing the observed pattern of lipid metabolism. The results from the present study also indicate compartmentalization of lipid metabolism in dehydrating peanut kernels.     

FURTHER OBSERVATIONS ON THE PATHOGENICITY OF CALONECTRIA RIGIDIUSCULA (BERK. & BR.) SACC. TO THEOBROMA CACAO L

Quantitative data are provided for the occurrence of Calonectria rigidiuscula and other fungi in occluded Mirid lesions and other sites in shoots of cacao plants. Mirid lesions appear to be particularly favourable for the development of C. rigidiuscula. The fungus also occurs as a saprophyte on cacao pods, and as a wound parasite in woody plants other than cacao; it was successfully introduced into plants of varied affinities by inoculation. C. rigidiuscula spreads from inoculations in cacao stems much more rapidly than other fungi. The results confirm that it is the most important fungus infecting Mirid lesions and causing dieback of cacao in West Africa.
Inoculation tests with a range of Amelonado and Trinitario clones suggested that the clones vary in their susceptibility to C. rigidiuscula , but the plant-to-plant variation was too great to conclude that any one is highly resistant. Various types of introduced cacao were also tested; preliminary experiments indicate that certain types of Upper Amazon cacao may be resistant, but they need further investigation.     

The Labelling of Malic and Citric Acids of Pea Leaves and Cotyledons of Germinating Peas by 14CO2 in the Dark

Leaflets of green pea plants and cotyledons of germinating peaswere kept in the dark in air containing ¹⁴CO₂. The malate extractedwas labelled to 35–40 per cent in the C-1 position andthe citric acid was labelled to 70–75 per cent in theC-6 position. This showed that two carboxylations, at least,were involved in both tissues, i.e. probably of a three-carbonacid to form malate, and of -oxoglutarate to form isocitrate.     

THE MUTUAL EFFECT OF RYEGRASS AND CLOVER WHEN GROWN TOGETHER

Italian ryegrass and a late-flowering red clover were grown together, with abundance of water and nutrients for both. It was found that even a small number of ryegrass plants reduced the growth of clover by 30%. This effect varied very little with increasing density of the clover crop.
The presence of clover reduced the ryegrass crop by an amount diminishing as the density of the ryegrass was increased. In a sparse crop of ryegrass, clover reduced the growth of the grass considerably more than did barley under comparable conditions.
There is no evidence of any specific effect of the roots of one plant on the other. When ample nitrogen is available the clover tends to take some that would otherwise be available for the grass and does not provide the grass with additional nitrogen.     

Minchinia teredinis N. Sp. (Balanosporida, Haplosporidiidae), a Parasite of Teredinid Shipworms

ABSTRACT. A new species of ascetosporan parasitizing tissues of woodboring mollusks of the genus Teredo , including T. navalis Linnaeus, T. furcifera von Martens, and T. bartschi Clapp, is described from light and transmission electron microscopical observations. The new species is assigned the name Minchinia teredinis sp. n. (Phylum Ascetospora, Class Stellatosporea, Order Balanosporida, Family Haplosporidiidae). Plasmodia, sporonts, sporocysts, and mature spores are found in all host tissues, but primarily in the gill. Spores are obovate, operculate, and characterized by four projections from the epispore membrane. The species is found from Long Island Sound to Virginia on the east coast of the United States. The parasite causes extensive damage to host tissues and is correlated with reductions in host populations.     

Tail skin of the dipnoan Neoceratodus larva: fine structure and differentiation

The fine structure of the tail skin oflarval Neoceratodusforsteri , between stages 40 and 50 (Kemp, 1982), is described and where applicable specific cellular components are compared and contrasted with comparable ones in the skin of adult dipnoans, teleosts and larval and adult amphibians.
The epidermis of the early developing tail, within the range studied, differentiates a variety of different cell types. Surface epithelial lucent and vacuolated lucent cells and basal cells are distinguished, and goblet (mucous) cells, Merkel cells and macrophages appear in the epidermis towards the end of the series.
Below a poorly developed collagenous basement lamella, immature melanophores with premelanosomes are present, and likewise there are non–myelinated nerves, some striated muscle fibres, capillaries and mesenchymal fibroblasts.
The tail epidermis is innervated by naked neurites from the beginning of the series, and the earliest recognizable Merkel cell is in synaptic association with neurites.