The Floral Nectaries of Hibiscus rosa-sinensis: 1. Development of the Secretory Hairs

Floral nectaries of Hibiscus rosa-sinensis occur on the lowerinner side of the fused sepals and each one consists of numerous(50000–55000) secretory hairs, occupying a cylinder-likezone completely lining the inner side of the sepals. Each hairoriginates from a single protodermal mother cell and, at maturity,it is built up of a basal cell, a stalk, 35–40 intermediatecells and a tip secretory cell. Development of protodermal cellsinto secretory hairs is asynchronous, the first cells to initiatedevelopment being those situated in the lowermost part of thecylindrical zone, and development progressing upwards. Volume increase of protodermal mother cells initiating developmentis accompanied by cell polarization manifested by organelledisplacement towards the apical region. Secretory hairs areformed through a sequence of transverse and, later on, anticlinaldivisions. Divisions of apical cells are preceded by well definedpre-prophase microtubule bands, which foreshadow the plane ofthe forthcoming division and predict with accuracy the sitesof parental walls where the new cell plate fuses at cytokinesis. Stalks consist of either one or two cells. Two-celled stalksoccur in 40 per cent of secretory hairs and derive from a transversedivision of one stalk cell; the wall formed is always depositedparallel to the proximal and distal walls, but never to thelateral ones. The significance of this mode of division is discussedin relation to the fact that lateral walls are entirely impregnatedwith a cutin-like material that blocks apoplastic movement ofsolutes. Hibiscus rosa-sinensis, nectaries, development, preprophase microtuble bands, stalk cells     

Plant-mediated effects of elevated ultraviolet-B radiation on peat microbial communities of a subarctic mire

Elevated ultraviolet‐B (UVB) radiation has been reported to have few effects on plants but to alter the soil microbial community composition. However, the effects on soil microorganisms have to be mediated via plants, because direct radiation effects are only plausible on the uppermost millimeters of soil. Here, we assessed secondary effects of UVB on soil microbes. The responses in the dominant plant Eriophorum russeolum, peat pore water and microbial communities in the peat were recorded at a subarctic mire in the middle of the third growing season under field exposure simulating 20% depletion in the ozone layer. The UVB treatment significantly reduced the sucrose and the total soluble sugar (sucrose+glucose+fructose) concentration of the plant leaves while increasing the sucrose concentration in the belowground storage organ rhizome. The starch concentration of the leaves was also slightly reduced by elevated UVB. In the plant roots, carbohydrate concentrations remained unaffected but the total phenolics concentration increased under elevated UVB. We suggest that the simultaneously observed decrease in bacterial growth rate and the altered bacterial community composition are due to UVB‐induced changes in the plant photosynthate allocation and potential changes in root exudation. There were no effects of elevated UVB on microbial biomass, peat pore water or nutrient concentrations in the peat. The observed responses are in line with the previously reported lower ecosystem dark respiration under elevated UVB, and they signify that the changed plant tissue quality and lower bacterial activity are likely to reduce decomposition.     

A role for SNX5 in the regulation of macropinocytosis

Background  

The mechanisms and components that regulate macropinocytosis are poorly understood. Here we have investigated the role of sorting nexin 5 (SNX5) in the regulation of macropinocytic activity.     

Influence of sociality on allometric growth and morphological differentiation in sponge-dwelling alpheid shrimp

Eusocial societies are defined by a reproductive division of labour between breeders and nonbreeders that is often accompanied by morphological differentiation. Some eusocial taxa are further characterized by a subdivision of tasks among nonbreeders, often resulting in morphological differentiation among different groups (subcastes) that specialize on different sets of tasks. We investigated the possibility of morphological castes in eusocial shrimp colonies ( Zuzalpheus , formerly part of Synalpheus ) by comparing growth allometry and body proportions of three eusocial shrimp species with three pair-forming species (species where reproductive females and males occur in equal sex ratios). Allometry of eusocial species differed in several respects from that of pair-forming species in both lineages. First, allometry of fighting claw size among individuals other than female breeders was steeper in eusocial than in pair-forming species. Second, breeding females in eusocial colonies had proportionally smaller weapons (fighting claws) than females in pair-forming species. Finally, claw allometry changed with increasing colony size in eusocial species; large colonies showed a diphasic allometry of fighting claw and finger size, indicating a distinctive group of large individuals possessing relatively larger weapons than other colony members. Shrimp are thus similar to other eusocial animals in the morphological differentiation between breeders and nonbreeders, and in the indication that some larger nonbreeders might contribute more to defence than others.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 527–540.     

A new hexaploid species of Centaurea section Acrolophus (Asteraceae) from Evvia Island,Greece

Centaurea carystea Trigas & Constantin., a new yellow‐flowered species of Centaurea from Mt. Ochi on Evvia Island (Greece), is described and illustrated. It is a member of the polymorphic C. section Acrolophus and allied to taxa of the C. attica aggregate, C. pelia and C. mantoudii. The new species appears to be a local and threatened endemic, with the total number of individuals known being less than 500. A karyological examination revealed that it is hexaploid, with 2n = 6x = 54, an unusual number in Centaurea, which may indicate a hybrid origin. To further clarify the taxonomic position of C. carystea , we used random amplification of polymorphic DNA markers of 25 plants belonging to nine species, subspecies and varieties morphologically related to the new species, together with two reference taxa. Clustering using the unweighted pair group method with arithmetic mean indicated a discrete position for C. carystea , close to but distinct from the yellow‐flowered C. mantoudii. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 762–774.     

Statistical and visual differentiation of subcellular imaging

Background  

Automated microscopy technologies have led to a rapid growth in imaging data on a scale comparable to that of the genomic revolution. High throughput screens are now being performed to determine the localisation of all of proteins in a proteome. Closer to the bench, large image sets of proteins in treated and untreated cells are being captured on a daily basis to determine function and interactions. Hence there is a need for new methodologies and protocols to test for difference in subcellular imaging both to remove bias and enable throughput. Here we introduce a novel method of statistical testing, and supporting software, to give a rigorous test for difference in imaging. We also outline the key questions and steps in establishing an analysis pipeline.     

Nest desertion by a cowbird host: an antiparasite behavior or a response to egg loss?

Natural selection can favor songbirds that desert nests containingeggs of the parasitic brown-headed cowbird (Molothrus ater).However, the high variability in desertion of parasitized nestswithin species is perplexing in light of the typically highcosts of parasitism. Because nest desertion can also be a responseto partial clutch predation, we first asked if Bell's vireos(Vireo bellii) deserted nests in response to the presence ofcowbird eggs (antiparasite response hypothesis) or to egg removalby predators and female cowbirds (egg predation hypothesis).Second, we asked whether variation in nest desertion was dueto intrinsic differences among individuals or to variation innest contents. We monitored a large number of nests (n = 494)and performed a clutch manipulation experiment to test thesehypotheses. The number of vireo eggs that remained in a nestwas a strong predictor of desertion both within and among pairs.Neither the presence of a single cowbird egg, which leads tonest failure for this host, nor the number of cowbird eggs receivedin a vireo nest influenced nest desertion. Furthermore, vireosdid not desert experimental nests when we immediately exchangedcowbird eggs for vireo eggs but deserted if we removed vireoeggs and replaced them with cowbird eggs the following morning.Desertion of parasitized nests by Bell's vireos can be almostentirely explained as a response to partial or complete clutchloss and does not appear to have been altered by selection frombrood parasitism.