AN ELECTRONIC TECHNIQUE FOR MONITORING THE TEMPORAL ASPECTS OF ACOUSTIC SIGNALS OF CAPTIVE ORGANISMS

ABSTRACT

We introduce an inexpensive electronic technique for monitoring the temporal aspects of any captive animal's acoustic signals. The electronic apparatus, attached to a data acquisition unit and personal computer, compares microphone output to a pre-set level and stores calling/non-calling data to disk. Total time calling and temporal signaling patterns of up to 256 individuals can be monitored for indefinite lengths of time. Sampling rate is adjustable, with a maximum rate of 6 samples/microphone/second. The capabilities of the system are illustrated with the field cricket Gryllus integer. Temporal aspects of acoustic signaling are discussed in terms of monitoring time scale and recognition of individual variation, energetics research, and hypothesis testing of the costs and benefits associated with mating success and predation.     

The Role of Leaves in the Perception of Vernalizing Temperatures in Sugar Beet

Annual and biennial sugar beet varieties require long days toinduce flowering but the biennial genotypes additionally requirevernalization. Previous research has suggested that the inabilityof non-vernalized biennial plants to flower can be explainedby a lack of competence of the leaves to respond to long days.In this study defoliation experiments were used to investigatewhich leaves could perceive long daylengths and, in particular,whether leaves initiated from a non-vernalized shoot apicalmeristem could perceive vernalizing temperatures and producea floral stimulus in long days. Annual and vernalized biennialplants flowered if young leaves (i.e. those formed during orafter vernalization) were kept on the plants, but they did notflower if only older expanded leaves (including those expandedprior to vernalization) were present. No evidence was obtainedto indicate that the older leaves contained inhibitors of floweringand it seems most likely that there is a decline in responsivenessto daylength with increasing leaf age. Exposure to vernalizingtemperatures accelerated flowering of the annual and was essentialfor flowering of the biennial. The presence of a single leafinitiated, but not expanded, prior to the transfer of biennialplants to vernalizing temperatures was sufficient to induceflowering. This indicates that expanding leaves do not needto be initiated from a vernalized apical meristem to becomecompetent to produce a floral stimulus in long days. Key words: Beta vulgaris L., sugar beet, vernalization, flowering     

Global and regional importance of the tropical peatland carbon pool

Accurate inventory of tropical peatland is important in order to (a) determine the magnitude of the carbon pool; (b) estimate the scale of transfers of peat‐derived greenhouse gases to the atmosphere resulting from land use change; and (c) support carbon emissions reduction policies. We review available information on tropical peatland area and thickness and calculate peat volume and carbon content in order to determine their best estimates and ranges of variation. Our best estimate of tropical peatland area is 441 025 km² (～11% of global peatland area) of which 247 778 km² (56%) is in Southeast Asia. We estimate the volume of tropical peat to be 1758 Gm³ (～18–25% of global peat volume) with 1359 Gm³ in Southeast Asia (77% of all tropical peat). This new assessment reveals a larger tropical peatland carbon pool than previous estimates, with a best estimate of 88.6 Gt (range 81.7–91.9 Gt) equal to 15–19% of the global peat carbon pool. Of this, 68.5 Gt (77%) is in Southeast Asia, equal to 11–14% of global peat carbon. A single country, Indonesia, has the largest share of tropical peat carbon (57.4 Gt, 65%), followed by Malaysia (9.1 Gt, 10%). These data are used to provide revised estimates for Indonesian and Malaysian forest soil carbon pools of 77 and 15 Gt, respectively, and total forest carbon pools (biomass plus soil) of 97 and 19 Gt. Peat carbon contributes 60% to the total forest soil carbon pool in Malaysia and 74% in Indonesia. These results emphasize the prominent global and regional roles played by the tropical peat carbon pool and the importance of including this pool in national and regional assessments of terrestrial carbon stocks and the prediction of peat‐derived greenhouse gas emissions.     

The Decline of Embryogenic Potential as Callus and Suspension Cultures of Carrot (Daucus carota L.) are Serially Subcultured

Callus and suspension cultures derived from seedling root segmentsof carrot can be assessed for their embryogenic potential (EP)by transfer of a standard culture inoculum to 25 ml culturemedium with 2,4-D omitted and incubation for a fixed period;the EP is expressed as the number of embryoids (0·5–2·5mm in length) developed per culture under these standard conditions.The initial decline in EP is indicative of increasing sensitivity,as culture proceeds, to inhibition by the auxin essential tocontinuing growth of the cultures. However, during culture changesoccur in the nuclear cytology of the cells leading to the appearanceof cells of impaired or nil totipotency and some such cellsare at a selective advantage so that eventually the cultures,as they are serially subcultured, no longer contain any totipotentcells. Normally the cells of such cultures have chromosome numbersin excess of the diploid complement. Evidence for the view thatthe cultures, as they exhibit declining EP, come to containa mixed population of cells comes from microscopic examinationof the cultures and from the isolation, cytological examinationand assessment of the EP of cell lines isolated by plating.Evidence that cells which lack totipotency and which in singleculture have similar growth rates to totipotent cells may neverthelessbe at a strong selective advantage in mixed culture is presentedfrom a study of the growth, and changing cellular compositionand EP during serial subculture of an artificially-preparedmixed culture initially containing equal numbers of diploidtotipotent cells and tetraploid cells lacking totipotency.