Embryoid Formation in Pollen Grains of Nicotiana tabacum

Anthers of Nicotiana tabacum (n = 24) were cultured on nutrientagar and examined at intervals for pollen embryoids. Embryoidswere formed in anthers of varying developmental stage, the youngestof which coincided with the liberation of free microspores fromtetrads, and the oldest with the formation of bicellular grains.This period in the development of the anther occupied 4–5days. Older anthers within this range were more successful thanyounger anthers. The first mitosis of the pollen was typicallyasymmetric and resulted in the formation of unequal generativeand vegetative cells. Some of the grains then went into a lagphase for at least 5–6 days, after which the mitotic conditionwas restored. Embryoids were formed by repeated division ofthe vegetative cell. If the generative cell divided, it didso only once or twice. Occasionally the first mitosis was symmetricand gave rise to equal cells, and in these instances both cellsprobably participated in embryoid formation. The youngest anthersexamined were probably less successful because fewer grainssurvived to enter mitosis. The number of embryoids produced varied considerably from oneanther to another both within the same bud and between differentbuds: values ranging from less than 400 to 10 000 per antherwere encountered. Most of these degenerated after the firstfew divisions, partly because they burst prematurely from thepollen grain wall. Embryoids which continued to develop formedplantlets and/or callus. The largest number of plantlets obtainedfrom one anther was 32. Haploid plantlets were also regeneratedfrom callus by transferring it to a low-sugar medium withoutauxin. The behaviour of grains not forming embryoids was also noted.     

THE APPLICATION OF THE DYNAMIC TRIANGLE OLFACTOMETER TO THE EVALUATION OF ORAL ODOR

The Dynamic Triangle Olfactometer, an instrument which measuresodor thresholds by a system functionally based on the principlesof steady state dynamic flow, dilution and forced choice triangledesign, was evaluated and found to be most acceptable for itsutility in appraising the efficacy of breath freshening formulationsin relieving or controlling extrinsic (onion) oral malodor. Initially, the olfactory acuity of a panel of novice judgeswas ascertained by the development of thresholds for hydrogensulfide and methyl mercaptan, both compounds related to oralmalodor, especially extrinsic as induced by an aqueous suspensionof onion oil used in this study. The threshold for onion oilwas also established. Several breath freshening formulationswere demonstrated to be effective in controlling extrinsic oralmalodor under the conditions of this study. The operational parameters of the DTO system were uncomplicatedand the data so obtained was reproducible. The panel of judgesapproximated the distribution of olfactory sensitivity of anormal population; therefore, the performance of the formulationsas measured in this system should be, and is, reasonably predictiveto a consumer population.     

Declining winter survival and fitness implications associated with latitudinal distribution in Norwegian Greylag Geese Anser anser

The Norwegian Greylag Goose Anser anser population has been increasing steadily over the past few decades, causing increasing nuisance in terms of agricultural crop damage. This, in combination with the importance of Greylags as a hunting target, has called for demographic estimates for the population to assist in management decisions. To this end, we analysed long-term mark–recapture data using Cormack–Jolly-Seber models embedded in program MARK to obtain survival estimates for the population. No sex-specific difference, or age effect on survival after juveniles had completed their first migration (3 months of age), was evident. Mean first-year survival was reported as 0.485 and annual survival of older birds as 0.700. On a monthly basis, survival in Greylags during summer and winter was very similar over the study period. A significant linear decline in winter survival from 0.909 to 0.807 was, however, apparent during the study period. Over the second half of the study (1994–2002), summer survival was about 3% lower than in the first half (1986–94) but no linear relationship was evident. We found a significant inverse relationship between Greylag survival during summer and latitudinal distribution in Norway. A similar relationship was evident between survival and annual bag numbers. The changes in adult survival observed in this study are likely to have had a substantial impact on the growth rate of the Norwegian Greylag population.     

Specific immunological response against the granulosis virus of the codling moth (Cydia pomonella) in woodmice (Apodemus sylvaticus): field observations

Antibodies specific to the granulosis virus (GV) of the codling moth (Cydia pomonella) were detected by indirect ELISA in sera of woodmice (Apodemus sylvaticus) trapped in an apple orchard sprayed by tractor-drawn mist blower with 2 × 10¹³ virus granules C. pomonella GV/ha. Such antibodies were absent from sera of mice trapped before virus had been applied. Virus antigens were detected by double antibody sandwich ELISA on the ground in and around the orchard and also in the faeces of woodmice inhabiting the orchard, but did not persist from one year to another. Some, but not all, of the samples containing virus antigens were found to be infective.     

Respiratory strategies of tenebrionid beetles in arid Australia: does physiology beget nocturnality?

Abstract The respiratory patterns and role of mesothoracic and abdominal spiracles in gas exchange are examined using flow‐through respirometry in three species of Heleini beetles from the Simpson Desert, central Australia. Two species, Helea (Heleus) waitei and Helea sp., show a form of continuous respiration with 70% and 75% of the CO₂ being emitted from the mesothoracic spiracles, respectively. Their mass specific metabolic rates are similar and similar to other nocturnally active desert‐dwelling tenebrionid beetles. Brises blairi also shows a continuous form of respiration, with 66% of CO₂ being emitted from the mesothoracic spiracle but has a significantly higher mass specific metabolic rate. Unusually for arid‐dwelling tenebrionid beetles, all three of the study species are confirmed to be exclusively nocturnal. There is no evidence that this activity pattern is driven by current ecological factors, such as competition or predation, and it is proposed instead that nocturnality arises from physiological constraint. Heleini probably evolved under mesic conditions and lack some of the key physiological adaptations to reduce water loss that characterize day‐active tenebrionid beetles in arid environments elsewhere. In consequence, they are able to exploit arid conditions only by restricting their activity to the most benign phase of the 24‐h cycle.