P. Barry

Rumen anaerobic fungi and plant substrate colonization as affected by diet composition

Abstract The influence of diet composition on rumen fungal population was studied by offering successively to a rumen fistulated cow 11 different diets rich in fibre, starch or soluble carbohydrates. At the same time, the colonization of four different plant substrates introduced into the rumen in nylon bags (soya bean teguments, lucerne stems, maize stalks and beet pulps) was investigated. The population of rumen anaerobic fungi, particularly abundant with lignocellulose-rich diets, decreased with starch or soluble-carbohydrate-rich diets; the fungi selectively colonized the plant tissues with thick or lignified cell walls of soya bean tegument, lucerne or maize stalks, but seldom the beet pulp. The development of rumen fungi depended both on the substrate on which they became attached and on the ruminal medium. The fungi, which were normally present in the duodenum, caecum and faeces, were eliminated by the unfavourable diet but rapidly proliferated once the feed ingredients became more favourable.

Colonization of thick-walled plant tissues by anaerobic fungi

Abstract An abundant colonization of thick-walled tissues, lignified in the case of wheat straw and maize stem, or non-lignified in the case of soya-bean hulls, by anaerobic rumen fungi was observed during an ultrastructural study of the degradation of plant cell walls in the rumen. It is suggested that fungi are able to digest cellulose and hemicellulose even when those carbohydrates are present in lignified cell walls.

Antennal olfactory sensilla of the parasitoid fly, Pseudoperichaeta nigrolineata Walker (Diptera : Tachinidae)

Abstract The antennal sensilla of male and female Pseudoperichaeta nigrolineata Walker (Diptera: Tachinidae) were studied by scanning electron microscopy. Five types of sensilla were identified on the funicle. The trichoid sensilla are most conspicuous, with a characteristic distal curvature and wall pores. Basiconic types I and II sensilla show a small peg with a pitted surface. Basiconic type III sensilla can be distinguished from the preceding ones by the swelling of the distal region of the peg. The function of these sensilla is likely to be olfactory. Coeloconic sensilla consist of a short grooved peg sunk in a socket. The number and distribution of the sensilla of each type are described. Female antennae bear more basiconic sensilla than those of males. These results are compared with previously published studies on other muscoid species.

Immunogold labelling of arabinoxylans in the plant cell walls of normal and bm3 mutant maize

Summary— Polyclonal antibodies directed against α, l‐1.2‐arabinofuranosyl poly‐β,d‐1.4‐xylopyranosyl (degree of polymerization 130) have been raised from rabbits. The immunogold labelling in transmission electron microscopy (TEM) evidenced the arabinoxylans of the plant cell walls. Comparison between the stems of normal and mutant bm3 maize demonstrated a greater accessibility of arabinoxylans in the walls of the mutant maize. The method, specific and swift, allows us to specify the repartition in the different parts of the stem: sclerenchyma, fibers, parenchyma.

Les métabolites de surface foliaire (phylloplan): présence et rôle dans les relations plante-insecte

Summary The phylloplane (leaf surface) is the interface between the plant and its environment. It is thus of great ecological interest. Our aim was to determine precisely the influence of its biochemical composition on insect host plant selection for oviposition. The plants considered in this study were maize, sunflower and leek. Plants were grown in hydroponic cultures in green houses to different phenological stages. A reproducible collecting method for water soluble substances such as soluble carbohydrates, free amino acids and organic acids was adapted. This improved technique was devised for microlocalization of monosaccharides. A major difficulty was the very low quantities of measured chemicals. These varied from 10−5 to 10−6 moles m−2 of leaf surface. Ratios of free amino acids were very constant and characteristic of each plant species. The quantities of soluble carbohydrates found within the plant tissues bore a direct relationship to those found on the phylloplane. The first results concerning ...