The functional significance of leaf structure: a search for generalizations

The coupling between leaf structure and function is illustrated with reference to two examples, the C₄ photosynthetic pathway and leaf pubescence. A distinction is made between function and functional significance. The latter is defined as the role, significance or consequence of a structure, whereas the former is more simply the action that a structure is capable of performing. Using the two examples, four generalizations are made concerning the relationships between structure, function and functional significance: the functional significance of leaf structure is environment-dependent; the relationship between functional significance and structure is sometimes non-intuitive; functional equivalency means that there is often more than one 'solution' to the same 'constraint'; and the consequences of leaf structure can exert profound effects at levels of organization beyond those of the individual organism and may play a critical role in determining community structure and function, through interactions with other species and trophic levels. The importance of understanding the consequences in variation in leaf structure at the global scale is illustrated with reference to the issue of global climate change.     

Patterns of variation in the acoustic calling signals of Chloriona planthoppers (Homoptera: Delphacidae) coexisting on the common reed Phragmites australis

Populations of the Tour species of Chloriona commonly found in the Netherlands C dorsata, C. glaucescens, C. smaragdula and C. vasconica –were cultured in the laboratory on Phragmites australis, their exclusive host plant in the field. The low frequency substrate-transmitted signals produced during the calling phase of mating behaviour were digitally analysed for the males and females of each species. Variables selected to cover most aspects of the call were measured, and variation was quantified within species and statistically tested among species using univariate and multivariate techniques. The calls of the males were more complex in structure than those of the females, with two different phase patterns recognized, and were species-specific. C. glaucescens and C vasconica were also separated on variables of the female call, but C dorsata and C. smaragdula completely overlapped. No significant differences were found between the calls of the long-winged and.short-winged female morphs of C. smaragdula. A possible role for variation in calling signals, and responses to them, in the evolution and maintenance of reproductive isolation in Chlonona is discussed.     

Asexual Reproduction, Population Structure, and Genotype-Environment Interactions in Sea Anemones

Our studies of sea anemones reveal that asexual reproductioncan lead to the amplification of particularly successful genotypesPopulations of Haliplanella luciae studied to date are characterizedbv exclusively asexual reproduction and typically are dominatedby one or a few clones A field translocation experiment suggeststhat this population structure may result from differentialmortality among colonizing clones most of which are not preadaptedto local conditions Asexual reproduction by survivors leadsto extensive multiplication of one or a few genotypes Metridiumsenile reproduces sexually and asexually and we ofler evidencethat there is significantly less vegetative proliferation butlarger individual body size in areas of low tidal current velocitythan in areas of moderate to high velocities This may indicatethat small individuals (produced asexually) are at a particularfeeding disadvantage in slowly moving water leading to an emphasison maintaining individual body sizeat the expenseol asexualleproduction Individuals heterozygous fora phosphoglucose isomerase(PG1) locus appear to be more successful than homozygotes inmaximizing body size independent of current regime and in maintaininglarge clone biomass in low velocity habitat Members of heterozygoteclones are significantly more dispeised some clonemates beingseparated by 9 meters or more and are overrepresented in thelow velocity habitat Selection against (small) homozygotes activechoice of habitat, and passive differential dispersal of larvaeand adult anemones may all contribute to this pattern.     

Mechanism of Host Cell Restriction in African Green Monkey Kidney Cells Abortively Infected with Human Adenovirus Type 2

Host cell restriction by GMK cells in abortive infections of adenovirus type 2 can be partially relieved by co-infection with SV40.     

Microbiological Synthesis of Fat: PRELIMINARY SURVEY OF THE FAT-PRODUCING MOULDS

1. A survey of potential fat-producing moulds has shown that atleast 40 strains from 10 species are of interest.
2. These havebeen grown on five different media and A. nidulans,P. spinu-losum,P. javanicum, P. piscarium, P. flavo-cinereum,P. oxalicum,A. flavus, A. flavipes have shown the most promise.
3. The fatcontent on felt weight was maximal at 39?7 per cent,with A.flavipes and 34?6 per cent, with F. lini, and on usedsugarwas maximal at 9?3 per cent, with A. flavipes and 6?7per cent,with A. nidulans.
4. The potential value of micro-organisms asfat producers is discussedwith reference to the moulds.

     

Growth Factors for Mycoplasma pneumoniae in Yeast and Tissue Extracts

1. Many tissue extracts have been shown to have growth factor activity towards M. pneumoniae notably bovine lung. Yeast extract is therefore not unique in this respect. The materials in lung digest and in yeast extract are very similar in properties and could be identical.
2. The growth factor is a low molecular weight water soluble material. Despite its stability to heat it decomposes on storage, presumably by oxidation.
3. Chromatographic procedures, on both Dowex 50W columns and on paper, indicated the presence of two active components.