Enhancer trap expression patterns provide a novel teaching resource

A collection of Arabidopsis enhancer trap transposants has been identified for use as a teaching tool. This collection serves to assist students in understanding the patterning and organization of plant tissues and cells, and will be useful in plant anatomy, morphology, and developmental biology courses. Each transposant exhibits reporter gene expression in a specific tissue, cell type, or domain, and these lines collectively offer a glimpse of compartments of gene expression. Some compartments correspond to classical definitions of botanical anatomy and can assist in anatomical identification. Other patterns of reporter gene expression are more complex and do not necessarily correspond to known anatomical features. The sensitivity of the beta-glucuronidase histochemical stain provides the student with a colorful and direct way to visualize difficult aspects of plant development and anatomy, and provides the teacher with an invaluable tool for a practical laboratory session.     

Contrasting resource allocation patterns in Sedum lanceolatum Torr.: Biomass versus energy estimates

Summary Biomass determinations and microbomb calorimetry were used to assess resource allocation in Sedum lanceolatum Torr. between 2,257 and 3,726 m above sea level in the Front Range of the Rocky Mountains, Colorado, USA. In general, energy values did not differ within a tissue among sites, but did differ among tissue types. Flowers and leaves had the greatest energy content per gram ashfree dry weight. Total kilojoules per plant were homogeneous along the elevational gradient.Allocation patterns based on kilojoules of energy and grams of biomass were not highly correlated, with the exception of the percent investment in sexual tissues. Allocations to sexual tissues based on dry weight and energy were negatively correlated, revealing opposing trends of sexual investment with the increase in elevation. Due to the greater biomass investment in high energy leaves and flowers by populations of Sedum lanceolatum at higher elevations, allocation to sexual reproduction based on calorimetric analysis increased from 18.3 to 38.3% along the 1,469 m change in elevation. Although biomass can represent energy allocation in some taxa, for those species that change morphologically or physiologically along an environmental gradient, these two methods may not reveal similar trends.     

Changing patterns of carbon allocation in lake phytoplankton: an FTIR analysis

Fourier transform infra-red (FTIR) spectroscopy was used to assess carbon allocation in selected phytoplankton (Pediastrum duplex, Ceratium hirundinella, Anabaena flos-aquae) in a eutrophic lake. In contrast to bulk-analysis techniques, FTIR spectroscopy can provide information on carbon allocation at the species level within natural mixed populations. Carbon allocation was determined using lipid/protein (L/P) and carbohydrate/protein (C/P) ratios and multivariate analysis of complete spectra and showed considerable intraspecific heterogeneity within samples dates, and clear seasonal changes in the spectra of Pediastrum and Anabaena, with both alga showing increased L/P and C/P ratios on selected sampling dates. Although increased ratios can indicate nutrient deficiency, the alga were not nutrient deficient during these periods, as indicated by continued population growth and high (>0.1%) internal phosphorus concentrations. FTIR spectra from Ceratium did not show any clear seasonal change. In all three algae, the transition from population growth to decline was not accompanied by any significant change in ratios, nor were low epilimnetic nutrients correlated with increased ratios, marking a significant contrast to laboratory batch cultures (previous studies) where low nutrients and the transition to stationary phase led to marked spectral changes.     

Malaria in Birmingham and a London teaching hospital.

During the past five years the incidence of imported malaria increased among patients seen in East Birmingham Hospital and in St Thomas''s Hospital, London. Plasmodium vivax was the predominant species in Birmingham, and was almost always acquired by Asian immigrants visiting the Indian subcontinent. In St Thomas''s P falciparum was most commonly imported, usually by African immigrants visiting Nigeria and Ghana. Two patients (one Irish, one Japanese) died of falciparum malaria after visiting tropical Africa. In both hospitals the immigrant patients had seldom taken prophylactic drugs, and the few who had, ceased to do so on arrival in the UK and sometimes before leaving the malarious country. Apparently immigrants who visit their homeland do not consult their general practitioners before travelling, are given inappropriate advice, or do not take appropriate advice when given. Since the incidence of imported falciparum malaria in the UK is rising, the following points should be considered: the infection may be lethal, particularly in patients lacking immunity; it can mimic other diseases, which may lead to delayed diagnosis; severe disease may be associated with few parasites on a blood film, and even if the result is negative further tests should be performed; clinicians and hospital pharmacists should be aware of the need to keep permanent stocks of parenteral chloroquine and quinine preparations.     

Food resource allocation patterns in lactating females in a long-term selection experiment for litter size in mice

Resource allocation patterns, as quantified by residual food intake (RFI), and the consequences for offspring development were investigated during lactation in 96 females of a mouse line selected for 104 generations for high litter size at birth (S-line) and in 87 females of a non-selected control line (C-line). Litters of 45 C-line dams (Cs) and 48 S-line dams (Ss) were standardised (s) at birth; other dams (ns) supported total number of pups born (Cns and Sns, respectively). RFI during lactation was significantly lower in Sns-dams than in C-line dams and Sns-dams. After weaning Sns-dams seemed to be able to restore the negative resource situation. Sns-pups were about 25% less mature than Cns-pups at all times. Maturity was similar for Cs- and Ss-pups from 2 d in lactation on, and about 18% and 53% higher than Cns- and Sns-pups. The pre-weaning mortality rate was significantly higher in Sns-litters (35.6 ± 2.76) than in Cns-litters (4.95 ± 2.23). The results suggest that S-line dams allocated considerably more resources to maintenance of offspring than C-line dams. This was insufficient to provide the offspring with an adequate amount of resources, resulting in reduced pup development and increased pre-weaning mortality rates.     

Experimental manipulation of patterns of resource allocation in the growth cycle and reproduction of Smyrnium olusatrum L.

Plants of the monocarpic (normally biennial) Smyrnium olusatrum (Umbel]iferae) were grown in pots in soil at a high or low nutrient regime. Some plants receiving full nutrients were grown in a heated glasshouse with 16 h days. The remainder were grown without supplementary lighting or heat and included control plants and others which received surgical treatment after ten months growth: deradication (removal of half of the root stock); defoliation; deradication and defoliation. The distribution of plant biomass and of phosphorus were analyzed at the time of seed set.
Patterns of allocation of dry matter and phosphorus were quite different and were significantly altered by treatments, which produced a range of allocation to reproductive structures ranging from 21 to 74% of total phosphorus and 12 to 35% of dry matter.
Distribution patterns of total phosphorus are discussed in terms of the potential demands being made by alternative structures and functions over the life cycle of the plants.     

Manipulating resource allocation in plants

The distribution of nutrients and assimilates in different organs and tissues is in a constant state of flux throughout the growth and development of a plant. At key stages during the life cycle profound changes occur, and perhaps one of the most critical of these is during seed filling. By restricting the competition for reserves in Arabidopsis plants, the ability to manipulate seed size, seed weight, or seed content has been explored. Removal of secondary inflorescences and lateral branches resulted in a stimulation of elongation of the primary inflorescence and an increase in the distance between siliques. The pruning treatment also led to the development of longer and larger siliques that contained fewer, bigger seeds. This seems to be a consequence of a reduction in the number of ovules that develop and an increase in the fatty acid content of the seeds that mature. The data show that shoot architecture could have a substantial impact on the partitioning of reserves between vegetative and reproductive tissues and could be an important trait for selection in rapid phenotyping screens to optimize crop performance.     

Energetic costs, underlying resource allocation patterns, and adaptive value of predator-induced life-history shifts

We studied costs and benefits of life history shifts of water fleas (genus Daphnia ) in response to infochemicals from planktivorous fish. We applied a dynamic energy budget model to investigate the resource allocation patterns underlying the observed life history shifts and their adaptive value under size selective predation in one coherent analysis. Using a published data set of life history shifts in response to fish infochemicals we show that Daphnia invests less energy in somatic growth in the fish treatment. This observation complies with theoretical predictions on optimal resource allocation. However, the observed patterns of phenotypic plasticity cannot be explained by changes in resource allocation patterns alone because our model-based analysis of the empirical data clearly identified additional bioenergetic costs in the fish treatments. Consequently, the response to fish kairomone only becomes adaptive if the intensity of size selective predation surpasses a certain critical level. We believe that this is the first study that puts resource allocation, energetic costs, and adaptive value of predator induced life-history shifts – using empirical data – into one theoretical framework.     

A general analysis of resource allocation by competing individuals.

A linear model for population dynamics in a stationary stochastic environment is introduced based on linearizing the N-species Lotka-Volterra competition equations in discrete time. Iteration of the linear model shows the sequence of population sizes to be formed from a simple linear operation on the sequence of carrying capacities. The transfer function for this operation is calculated and the spectral properties of time series data on population size follow directly.The above approach is illustrated with a symmetrical two-species competition system assuming white noise variation in the carrying capacities. The results are interpreted in detail with the following ideas. (1) The intrinsic rate of increase governs the “responsiveness” of the population to changes in the carrying capacity; (2) one effect of competition is to reduce the “effective rate of increase” of the population. Increasing competition can produce effects identical to that of lowering the intrinsic rate of increase; (3) the other effect of competition is to communicate the stochastic variation in one species' carrying capacity to its competitors. The end result of this communication depends critically on the cross-correlation scheme among the carrying capacities of the competing species.