A revision of the Dip lop salts group of dinoflagellates (Dinophyceae) based on material from the British Isles

SEM has made possible a detailed re-examination of the thecal plates of marine dinoflagellates belonging to the Diplopsalis group which have been collected in an extensive survey of the seas around the British Isles. Six genera are recognized: Diplopsalis, Diplopsalopsis, Dissodium, Oblea, Zygabikodinium and die new genus and species Boreadinium pisiformis Dodge 8c Hermes. The confused taxonomic history of the group is discussed, the valid species are listed and a key for the identification of the genera is given.     

Resource density regulates the foraging investment in higher termite species

1. Resource density can regulate the area that animals use. At low resource density, there is a conflict in terms of balance between costs of foraging and benefits acquired. The foraging of the higher termite Nasutitermes aff. coxipoensis consists of searching throughout trails and a building galleries phase. 2. In this study, a manipulative field experiment was used to test the hypothesis that colonies of N. aff. coxipoensis forage towards a more profitable balance between the establishment of trails and gallery construction at low resource density. 3. The experiment was conducted in north‐eastern Brazil. Seven experimental plots were established with a continuous increase in resource density (sugarcane baits). Entire colonies of N. aff. coxipoensis were transplanted from their original sites to the experimental plot, totalling 35 nests. The number, branches and total length of trails and galleries were quantified. 4. The results show that N. aff. coxipoensis optimises its foraging output, intensifying the establishment of trails at the cost of gallery construction when resource density is low. The number of trails, the number of trail branches and the total length of trails decreased with increasing resource density. Interestingly, at low resource density, the search effort was concentrated on forming longer and a greater number of trails, a small proportion of which were converted into galleries. The opposite relationship was observed at high resource density. 5. These results suggest an optimisation of search efforts during foraging depending on resource density, a mechanism that may help researchers to understand the use of space by higher termite species.     

A survey of thecal fine structure in the Dinophyceae

The structure of the theca of some 30 marine and freshwater members of the Dinophyceae has been examined by light and electron microscopy. The basic arrangement of membranes, an outer continuous plasma-membrane beneath which lies a single layer of flattened vesicles, is the same in all flagellated forms. The periplast of coccoid and encysted forms is somewhat different. Thecae have been found to fall into eight reasonably distinct categories as follows: (1) Outer membrane underlain by irregular vesicles. (2) Membrane underlain by close-packed vesicles. (3) As Group 2 but with plug-like structures attached to the inner membrane of the vesicles. (4) As Group 2 but with thin plates within the vesicles and all plates of more or less similar shape. (5) As Group 4 but plates have slight overlap. (6) Similar to Group 5 but plates are reduced in number and can be individually recognized. (7) As Group 6 but plates have elaborate flanges and their surfaces are covered by reticulations. (8) Theca mainly consisting of only two plates. It is suggested that the thecal types could from the basis for some revision of the taxonomy of the class.     

Some Biochemical Effects of Glyphosate on Plant Meristems

Glyphosate promoted the activity of phenylalanine ammonia lyase(PAL) in both single node rhizome buds of Agropyron repens androot tips of wheat seedlings, in the latter case correlatinginversely with decline in respiratory activity. Differentialrates of ¹⁴C-amino acid incorporation suggest that glyphosatedepleted the phenylalanine protein precursor pool with resultantinhibition of protein synthesis, as evidenced by a rapid declinein the level of ‘soluble’ protein. Promotion ofPAL is assumed to occur by derepression through decline in end-productlevels. Activities of shikimate: NADP oxidoreductase (SORase),chorismate mutase, and polyphenol oxidase (PPO) were also elevated,but to lesser extents than for PAL.     

Modifications of chloroplasts of flax cotyledons treated with monuron: myelinoid figures formed under low light conditions

Abstract. Monuron treatment of flax cotyledons in the dark and at a low light intensity of 0.2 Wm⁻² caused a retardation of chlorophyll breakdown. With low light, carotenoid breakdown occurred more rapidly, suggesting a possible overloading of the carotenoid protective system, but in darkness chlorophyll loss was first. The ultrastructure of treated leaves was markedly altered. In the dark, monuron caused a swelling of the chloroplasts and a subsequent disruption of the thyl-akoids resulting in a concentric membrane formation in the stroma. Following envelope rupture the thylak-oid system was visible as a myelinoid figure in the cytoplasm.