The balance between the foliage projective covers of overstorey and understorey strata in Australian vegetation

Foliage Projective Cover of the overstorey (canopy) of a‘climax’community appears to reach an equilibrium value determined largely by the prevailing climate. Overstorey FPC decreases in‘climax’communities in a graded series from humid to arid regions. Understorey cover (of all strata below the canopy) in‘climax’communities attains a balance with overstorey FPC. Disturbance (gaps, microhabitats, fire, overgrazing, invasion of woody weeds, etc.) may reduce the overstorey cover which will be compensated by an increase in understorey cover. Secondary succession back to the‘climax’structure will follow a path maintaining an inverse linear relationship between understorey cover and overstorey cover. At the same time, species diversity appears to decrease as overstorey cover increases.     

Nutritional Study of Three Strains of Naegleria gruberi*

Naegleria gruberi strains cloned from amebas isolated from a Vero cell culture (“TS”), a sewer drainage ditch (“PD”), and an established laboratory line (“S”) were morphologically identical except for differences in size and flagellate transforming ability. Cultivation on a Trypticase-yeast extract-glucose medium (“TYG”) fortified with autoclaved E. coli resulted in increased cell size of 2 strains. Differences also were noted in growth rates and optimal growth temperatures. The autoclaved E. coli in TYG medium was replaceable with serum only for strains TS and PD. A basal salts medium + autoclaved E. coli supported growth of all 3 strains, but the basal salts medium + serum would not support growth of any of the strains.     

The Influence of Leaf Removal upon the Development of the Grain of Winter Wheat

The paper describes the effects on grain development of theremoval of half the flag leaf, the entire flag leaf and allthe leaves from selected main shoots of a field crop of wheat,cultivar Maris Ranger, 7 days after anthesis. None of the treatmentsreduced grain weights in the 14 days following defoliation.Even in the next 14 days only the more severe defoliations reducedgrain weight, with the most severe treatment causing the greatestreduction. Ultimately the rate of grain growth in plants onwhich only a half of the flag leaf had been removed also fellbehind that of the controls. Final grain yields were in theorder, control plants, > plants with half the flag leaf removed,> the entire flag leaf removed, > all the leaves removed.The significance of these results in interpreting the factorslimiting grain growth in wheat is discussed.     

Specific Ribonucleoprotein Fragment from the 30S Subunit of <Emphasis Type="Italic">E. coli</Emphasis> Ribosomes

WE describe here a new approach to the determination of the three dimensional arrangement of the proteins within the ribosome, based on controlled degradation with nuclease. We suggest that by isolating ribonucleoprotein (RNP) fragments and determining which particular proteins each fragment contains, it should eventually be possible to construct a detailed “map” of the protein arrangement. The “mapping” problem has already received attention in various laboratories. Mizushima and Norrtura¹ have shown that the proteins of the E. coli 30S ribosomal subunit assemble with 16S RNA in a highly specific order. Further, the reactivity of the 30S particle towards proteolytic enzymes² and protein-modifying reagents³ shows a striking correlation with Mizushima and Nomura's “assembly map”¹, in that the first group of proteins in the assembly process seems to be protected in the completed particle.     

Indole(ethyl)amine N-Methyltransferase in Human Brain

TANIMUKAI et al.¹, using gas-liquid separation, correlated the appearance of a bufotenin-like substance in urine and the onset of psychosis in latent schizophrenics brought on by administration of a monoamine oxidase inhibitor with amino-acid precursors of indoleamines and methyl groups. Serious doubt about endogenous bufotenin as the cause of psychiatric disturbance was cast by research demonstrating that intravenously administered bufotenin produced nothing but bizarre cardiovascular symptoms in man^{2, 3}. One objection to such work is that bufotenin may not easily cross the blood-brain barrier. Recent preliminary evidence gathered in our laboratories from rats infused intraventricularly with bufotenin has suggested that this substance is at least as potent as its powerfully hallucinogenic 5-methoxy congener (unpublished results of D. Segal and A. J. M.).     

Evidence for a Link Between Division and Differentiation in Entamoeba invadens

SYNOPSIS. Growth curves in a monophasic, polyxenic medium are presented for a strain of Entamoeba invadens. Three characteristics of these curves are: 1) the increase in numbers of trophozoites is linear with time; 2) the increase in numbers of cysts is linear with time; and 3) the durations of these 2 periods are equal to each other. Additional experiments are described in which variations of the culture conditions do not alter these 3 characteristics. Because of these data, we propose that, under the cultural conditions we have used, division of the trophozoites of Entamoeba invadens is coupled to the differentiation of these cells into cysts.     

Breeding populations of the Hobby Falco subbuteo on farmland in the southern Midlands of England

Site occupancy, dispersion, density and nest sites of Hobbies Falco subbuteo were studied in two areas of farmland in the English southern Midlands between 1975 and 1983. Nesting ranges were identified within which Hobby nests were regularly found but which contained only one pair of birds in any one year. Breeding was not proved in all nesting ranges in every year. Within nesting ranges, birds sometimes used the same nest in consecutive years but nests were also commonly found more than 1 km apart in consecutive years. The mean nearest-known-neighbour distance between simultaneously occupied breeding sites was 4 6 km (range 20-9.6 km) and the minimum estimated densities of Hobbies in the two study areas were 3.8 and 4.8 nesting ranges/100 km. Small inter-nest distances, less than 30 km, were recorded only in the area with the lowest density. Hobbies nested in old Crow Corvus corone nests in a wide range of tree species but prior to the onset of Dutch elm disease, elms Ulmus spp. were probably used almost exclusively in one of the areas. It is concluded that substantial numbers of Hobbies nest on farmland north of the River Thames, outside what has been traditionally regarded as the main range of the species, and that previous published estimates of the size of the British population have been far too low.