Reproductive physiology in relation to deer management

One of the more important aspects of deer management is the regulation of the number of animals in the herd. It is the fertility and fecundity of the female, rather than the male, that affects the rate of increase and the number of female deer that affects the size of the population. The various parameters of reproductive physiology of female deer are discussed and the information available with regard to the species of deer occurring wild in Britain is reviewed and summarized. The time of year to cull deer and the importance of the female as well as the male for selection for breeding are briefly discussed.     

Ultrastructural Changes in the Nucleoli of Jerusalem Artichoke (Helianthus tuberosus) Tuber Discs

Discs cut from Jerusalem artichoke (Helianthus tuberosus) tubertissue were shaken in distilled water at 25?C (termed ageing)for periods of 0, 3, and 24 h when samples were prepared forelectron microscopy. Tissue samples were fixed with 3 per centbuffered glutaraldehyde followed by osmium tetroxide. The ultrastructureof the nucleolus changes significantly with ageing. By 3 h aregion which we identify as nucleolar-organizing chromosomeis beginning to move from an external position on the nucleolusinto the fibrillar region. By 24 h this chromosomal region hasbecome dispersed as small areas within the fibrillar zone. Atthe same time the nucleolus develops a large granular zone.These changes are discussed with reference to the known increasein RNA synthesis during the ageing process.     

Control of the Breakdown of Food Reserves in Germinating Dicotyledonous Seeds -- a Reassessment

The correct interpretation of experimental data concerning theeffect of the embryonic axis upon food reserve mobilizationin dicotyledonous seeds depends on an awareness of the preciseincubation conditions used for treating the seeds. Under optimalincubation conditions excised cotyledons can develop hydrolyticactivities which are comparable to those produced in the intactsystem. A reasonable hypothesis to explain this suggests thatsuch hydrolytic enzyme activities automatically increase withincotyledons during germination and early seedling growth andare regulated by feed-back effects mediated by reserve breakdownproducts. If this conjecture is correct then the requirementfor an axis-derived hormonal influence on cotyledonary metabolismis not mandatory. Germination of seeds, hydrolytic activity, feed-back control, cytokinins     

Deterrent chemicals as a basis of oligophagy in Locusta migratoria (L.)

Abstract. (1) One hundred and two plants were offered to locust nymphs after a 5 h period without food. Large meals were only taken on grasses and on Juncus. Most dicotyledons were totally rejected.
(2) All the plants which were relatively unpalatable yielded an extract which reduced the amount eaten, but no inhibition of feeding was induced by extracts of plants which were freely eaten. Very few of the extracts increased the amount eaten.
(3) Over 100 chemicals, mostly non-nutritional, known to occur in leaves, were tested for their inhibitory effect on feeding. Some had no effect, but most progressively inhibited feeding as their concentration was increased until no feeding at all occurred. Chemicals of many classes had this effect, but alkaloids and monoterpenoids were the most consistently deterrent at the lowest concentrations.
(4) It is concluded that the failure to eat most plants results from the presence in the leaves of one or more chemicals in amounts which inhibit feeding. Grasses and a few other plants are readily acceptable because they do not contain deterrent chemicals in sufficient quantity to limit feeding.     

Experimental analysis of the pattern of tethered flight in the Queensland fruit fly, Dacus tryoni

ABSTRACT. The tethered flight of the Queensland fruit fly, Dacus tryoni Frogg. (Diptera, Tephritidae), was investigated, and the duration of each flight during a 2-h experimental period was recorded. The pattern of flight was analysed, and related to the age, sex and origin of the specimens, and to the availability of host fruit during the rearing of the adults. The effect of adult crowding on the pattern of flight was also briefly examined. The results indicated that the origin of the flies had little effect on the pattern of flight; male and female flies showed different trends with respect to the proportion of short flights undertaken as the flies matured; and the availability of fruit had a marked effect on the pattern of flight in recently mature flies. These data are discussed with respect to the dispersive/non-dispersive movements of the flies postulated from previously documented field data. It is suggested that there is a characteristic pattern of tethered flight, which can be related to the absence of hosts in the immediate environment, and would be likely to lead to greater dispersal under natural conditions.     

Localization of Glucose-6-phosphate Dehydrogenase Activity in Seeds and its Possible Involvement in Dormancy Breakage

A quantitative cytochemical analysis of glucose-6-phosphatedehydrogenase activity of deeply dormant seeds of Avena fatuashowed that although the enzyme activity is present in mostcell types of the embryo and seed, it is only in the embryothat activity is increased on treatment with GA₃ to break dormancy.This would appear to happen prior to any measurable embryonicaxis growth, and supports the idea that activation of the pentosephosphate pathway is an early event in dormancy break. A similar,though less marked, change occurred in less dormant seeds ofA. fatua, but could not be detected in dormant seeds of Lactucasaliva. Dry seeds of L. sativa and weakly dormant A. fatua containedtwice the activity seen in seeds imbibed with either water orGA₃, indicating that this might be a marker of low levels ofdormancy. Avena fatua, Lactuca sativa, seeds, dormancy, pentose phosphate pathway, cytochemistry, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase