Showing papers by "University of Aberdeen published in 1971"

Epicuticular wax in the stomatal antechamber of sitka spruce and its effects on the diffusion of water vapour and carbon dioxide.

Abstract: The distribution of wax tubes on the leaf surfaces is described, especially the presence of wax tubes in the antechambers of the stomata. The extra resistances which the wax-filled antechambers add to the other resistances in the pathway for diffusion of water vapour and of carbon dioxide are calculated. We conclude that the wax-filled stomatal antechambers reduce the rate of transpiration by about two thirds but reduce the rate of photosynthesis by only about one third. Thus wax-filled stomatal antechambers are excellent antitranspirants.

The distribution and abundance of sand gobies, Gobius minutus, in the Ythan estuary

Abstract: The aims of this study were, first, to describe the distribution and abundance of the sand goby (Gobius minutus) in the Ythan estuary and, when it became apparent that there were striking seasonal changes in the abundance of gobies, to attempt to explain these changes. Gobies were abundant in the estuary from July until January or February each year, and scarce for the rest of the year. The sharp drop in goby numbers in the estuary in January or February each year was associated with a change in the sex ratio from 50% females to 80% females, and a change in dispersion from aggregated to random, and a restriction of the gobies’range to the lower half of the estuary. It seemed to me that these associated changes should all be the result of a common cause. The disappearance of gobies in January or February was not a result of low water temperatures in the estuary in winter, nor was it the result of changes in water salinity. Measurements of food intake and available food supplies suggested that there was no shortage of food at this time. The disappearance was, however, associated with gonad maturation, suggesting that the loss of fish had something to do with the breeding requirements of the goby. I put forward the hypothesis that the loss of gobies in winter was the result of their migrating to sea to breed because their eggs would not develop in the estuary. I tested this hypothesis by attempting to capture gobies at sea, by measuring their salinity preference, and by attempting to rear their eggs at various salinities. I was unable to capture more than a few gobies outside the estuary. Ripe fish did not show any preference for high salinity water, and their eggs were intolerant of high salinities. It seemed, therefore, that my hypothesis of an emigration to sea to breed was incorrect, and that something else must explain the losses of gobies in winter, possibly heavy predation.

Turning behaviour as an index of the action of amphetamines and ephedrines on central dopamine-containing neurones.

Abstract: Summary 1 Rats lesioned unilaterally in the substantia nigra show no obvious abnormalities after recovery from the operation but rotate towards the lesioned side after administration of drugs of the amphetamine and ephedrine groups. 2 (+)-Amphetamine and (–)-amphetamine are equally potent in producing turning behaviour but (+)-methylamphetamine is considerably more effective. 3 (–)-Ephedrine (with a β-OH group on the ethylamine side chain) induces turning but only in doses approximately 20 times greater than (+)-methylamphetamine. 4 (+)-Norpseudoephedrine was the most effective of the ephedrine isomers tested followed by (–)-ephedrine and (+)-pseudoephedrine. 5 Turning produced by (–)-ephedrine and (+)-methylamphetamine is not reduced by FLA63 (50 mg/kg) 4 h previously, but is almost completely inhibited by α-methyl-p-tyrosine (150 mg/kg) 12 h previously. 6 Reserpine pretreatment potentiates turning produced by (–)-ephedrine. 7 Chlorpromazine (5 mg/kg) completely blocks turning induced by (+)-methylamphetamine although it concurrently increases exploratory activity. The level of exploratory activity after the (+)-methylamphetamine-chlorpromazine combination is more than 3 times that attained after saline alone.

The influence of the root system on the relationship between the rate of transpiration and depression of leaf water potential

Abstract: Summary The relationship between rate of transpiration and depression of water potential of the leaves (δψ1) was investigated with Gossypium hirsutum and Heliantlnis annum grown in water culture. (δψ1) was measured with a thermocouple psychrometer over a wide range of transpiration rates. The different transpiration rates were obtained by altering the environmental conditions in a climatological wind tunnel. At zero transpiration rate δψ1 was found to be 5.5 atm in H. annuus and 6.0 atm in Gossypium hirsutum. As the transpiration rate was raised, δψ1 rose steeply to a plateau in both species and remained at near to 9 atm within the transpiration range 0.4–2.4 g/dm2/hour. Thus within this range resistance in the plant declined in proportion to the transpiration rate. With transpirational fluxes greater than 2.4 g/dm2/hour, δψ1 rose, indicating little further decline in resistance. That the variable plant resistance is located in the roots was confirmed since plants with killed roots had a constant resistance, δψ1 exhibiting a linear relationship with transpiration. The resistance of the dead root system was much lower than that of living roots at low transpiration rates, but at high transpiration rates the resistance of living roots fell to about the same level as the dead roots. The implications of these findings are discussed.

Intertidal activity, breeding and the floating habit of Hydrobia ulvae in the Ythan estuary

Abstract: INTRODUCTIONEcological studies of Eider Somateria mollisima, Shelduck Tadorna tadorna, Redshank Tringa totanus [Aves], and Flounder Platichythys flesus [Osteichthys], in the estuary of the River Ythan, Aberdeenshire, have entailed investigations of their food requirements, and there is evidence to suggest that Hydrobia ulvae [Gastopoda], as a numerous food item common to all, may in some instances have influenced their breeding success and numbers in some years. In order to get an index of abundance of Hydrobia, the Ythan population has been sampled four times a year since May 1963. The full results of this sampling programme are being published separately. At the same time data on the annual cycle of Hydrobia were collected from one area (transect number 3, Fig. 1), on the assumption that breeding onset and intensity would be the same in other parts of the estuary in any one year.

Aerodynamic properties of a plant of complex structure

Abstract: Coefficients of momentum and vapour transfer of spruce shoots in a wind-tunnel are measured, and are shown to depend on shoot density: transfer per unit needle area becomes less effective as shoot density increases. Comparisons with theoretical values derived from established coefficients for 1 mm and 3 mm diameter cylinders (representing needles and twigs, respectively) indicate that the magnitude of the implied shelter effect is the same for water vapour as for momentum.

Gonad Development and Fecundity of the Sand Goby, Gobius minutus Pallas

Abstract: This paper describes gonad development and fecundity of the sand goby, Gobius minutus, in the Ythan estuary, Scotland. Sand gobies survived a maximum of about 22 months so that the longest lived fish experienced two breeding seasons. The gonads of underyearling fish matured in February, while those of yearling fish entering their second breeding season matured in December. Underyearling fish bred until June each year. The gonads of larger underyearling females increased in weight earlier than those of smaller underyearlings, but this did not appear to be true of the gonads of males. Fish size apparently did not influence the timing of the decline in gonad weight at the end of the breeding season. The maturing eggs in the ovaries of underyearling females could be recognized by December. In mature or ripe ovaries a second group of maturing eggs could be distinguished. The average fecundity of underyearling gobies was 2,556 in 1967 and 2,749 in 1968. Two of three yearling females had very low fecund...

Performance on a Sorting Task. A Cross-Cultural Experiment

Abstract: Comparaison de la performance, dans une t[acaron]che de classification, d'enfants ecossais et zambiens, different par l'[acaron]ge, mais de niveau scolaire equivalent. La t[acaron]che porte soil sur des modeles reduits (formes animales, vehicules), soit sur les photos en couleur de ces modeles, soit sur les photos en noir et blanc de ces modeles. Les resultats montrent, conformement a l'hypothese, que les enfants zambiens reussissent moins bien que les Ecossais, lorsque la t[acaron]che porte sur des photographies, alors qu'il n'y a aucune difference lorsqu'elle porte sur des modeles en trois dimensions. Chez les enfants zambiens, la classification par la couleur est plus frequente, conformement a l'hypothese, dans le cas des modeles, mais non dans celui des photographies en couleur. L'auteur discute brievement des implications de ces resultats.

The relation between electrical self-stimulation sites and catecholamine-containing neurones in the rat mesencephalon

Abstract: 72 electrodes implantees dans les mesencephales des rats ont ete examinees pour le comportement d'autostimulation. La majorite des sites positifs entourait le noyau interpedonculaire ou se situent des neurones dopaminiques.

Analysis of the post-infection growth stimulus in orchid mycorrhiza

Abstract: SUMMARY The sequence of symbiotic infection of Dactylorhiza purpurella protocorms shows that commencing shortly after infection there is a linear increase in length and breadth whereas growth of uninfected protocorms is negligible. From the time when external hyphae make physical contact with epidermal hairs of the host the processes of penetration, infection of the cortex and formation of the first pelotons occupy approximately 29 hours. There is a linear relationship between the number of pelotons and time but the size of protocorms is not directly related to the number of pelotons. Evidence suggests that stimulation of growth can take place before intracellular lysis of the endophyte occurs. In the absence of external nutrients infecting hyphae are rapidly lysed and little or no growth stimulus occurs. The hypothesis is posed that 'digestion' of the endophyte is a defence reaction not a pre-requisite for a growth stimulus and that nutrients are transferred across the living fungus-host interface and stimulate growth.

Inhibition of Botrytis cinerea spores by bacteria on the surface of chrysanthemum leaves

Abstract: Spores of Botrytis cinerea exhibited poor germination and growth in water drops on the surface of chrysanthemum leaves. The presence of B. cinerea spores in water drops placed on chrysanthemum leaves, or on plastic Petri dishes previously exposed to the air under chrysanthemum plants, resulted in an increased in the number of bacteria together with an inhibition of germination of spores added to the drops after their removal from the leaf. After separating the bacteria from the drops there was a stimulation of germination and growth of test spores. Re-addition of the bacteria resulted in a return of the inhibition. Of five isolates of bacteria from spore drops one caused marked reduction in the length of germ tubes of test spores. The results indicate that bacteria sedimenting on to leaves from the air could have an effect on the resistance of chrysanthemum to B. cinerea . There was no evidence of antifungal substances produced by the leaves or that phytoalexins were formed in response to spores of B. cinerea .

Effect of methohexitone, diazepam and sodium 4-hydroxybutyrate on short-term memory

Abstract: Short-term memory following the intravenous injection of methohexitone (0.15 mg/kg), diazepam (0.05 mg/kg) and sodium 4-hydroxybutyrate (10 mg/kg) has been examined by means of a visually presented digit retention test with intervals of 4 and 20 seconds before recall. No significant change was found with the 4-second interval; statistically significant impairment was found with the 20-second interval. It is postulated that the effect of these drugs is to accelerate decay of the memory trace, thus impairing its consolidation and producing anterograde amnesia. A versatile computerized test of short-term memory is described.

Critical flicker frequency after small doses of methohexitone, diazepam and sodium 4-hydroxybutyrate

Abstract: Statistically significant depression of critical flicker frequency has been measured following the intravenous injection of methohexitone (0.15 mg/kg), diazepam (0.05 mg/kg) and sodium 4-hydroxybutyrate (10 mg/kg). In the cases of methohexitone and diazepam the maximal measured changes (4.73 per cent and 7.07 per cent, respectively) occurred after 5 minutes and persisted for up to 90 minutes. After 4-hydroxybutyrate, depression was maximal at 15 minutes (4.32 per cent), but had disappeared by 30 minutes. No significant changes occurred after the injection of isotonic saline.

Effect of mild acute hypoxia on human short-term memory.

Abstract: Although there is considerable dispute about the minimum degree of acute hypoxia needed to impair human psychological performance, some workers have suggested that acute exposure to a PIO2 as high as 120 mm Hg may have a demonstrable effect on mental ability. We have investigated the effects, on human short-term memory, of acute exposure to simulated altitudes of 2,000 feet (PIO2≏;139 mm Hg), 8,000 feet (PIO2≏ 108 mm Hg) and 12,000 feet (PIO2≏92 mm Hg). There was no detectable difference between subjects' performances at the lower two altitudes; at 12,000 feet, however, short-term memory appeared to be impaired, although the impairment did not quite reach statistical significance (t=1.86; P≏0.07).

Orientation and Perception of Pictorial Depth

Abstract: Des echantillons d'ecoliers zambiens et ecossais sont soumis a une epreuve d'interpretation de dessin geometrique simple, presente selon deux orientations: la figure est symetrique soit par rapport a l'axe vertical, soit par rapport a un axe incline. Les resultats montrent que l'orientation affecte les reponses de l'echantillon ecossais: les reponses bi-dimensionnelles sont plus frequentes avec l'axe de symetrie vertical; mais ce n'est pas le cas pour les enfants zambiens. On ne constate aucun progres dans la discrimination des deux orientations avec l'[acaron]ge ou la scolarite dans l'echantillon zambien. L'auteur discute des implications de ces resultats.

Responses mediating pictorial recognition.

Abstract: (1971). Responses Mediating Pictorial Recognition. The Journal of Social Psychology: Vol. 84, No. 1, pp. 27-33.