Stipular extranuptial nectaries new to Polygala: morphology and ontogeny

Although taxonomic studies indicate that approximately one‐third of the genera of Polygalaceae have nodal glands, few anatomical data are available on the structure and ontogeny of these secretory organs. We studied the as yet unknown origin, structure and function of such glands in Polygala laureola. During field observations, we detected glucose in the secretion using Glicofita Plus® and visitors were recorded. Vegetative shoot apices and nodal glands were examined using light microscopy and scanning electron microscopy. The presence of glucose in the secretion allowed us to identify these nodal glands as extranuptial nectaries. Secretory cells occupy a medullary position and are surrounded by phloem. Vascular bundles are concentric, and xylem is only observed at the basal region of the nectary. Nectar is released during the daytime through a pore at the top of the nectary. A stipular origin was confirmed by the fact that the procambial strand is connected to the leaf trace, opposite the leaf gap. The occurrence of stipular extranuptial nectaries in a nodal position is new to Polygala. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 40–50.     

Rootstock-mediated changes in xylem ionic and hormonal status are correlated with delayed leaf senescence, and increased leaf area and crop productivity in salinized tomato

Tomato crop productivity under salinity can be improved by grafting cultivars onto salt-tolerant wild relatives, thus mediating the supply of root-derived ionic and hormonal factors that regulate leaf area and senescence. A tomato cultivar was grafted onto rootstocks from a population of recombinant inbred lines (RILs) derived from a Solanum lycopersicum  ×  Solanum cheesmaniae cross and cultivated under moderate salinity (75 m m NaCl). Concentrations of Na⁺, K⁺ and several phytohormones [abscisic acid (ABA); the cytokinins (CKs) zeatin, Z; zeatin riboside, ZR; and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC)] were analysed in leaf xylem sap in graft combinations of contrasting vigour. Scion leaf area correlated with photosystem II (PSII) efficiency ( F _v/ F _m) and determined fruit productivity. Xylem K⁺ (but not Na⁺), K⁺/Na⁺, the active CK Z, the ratio with its storage form Z/ZR and especially the ratio between CKs and ACC (Z/ACC and Z + ZR/ACC) were positively loaded into the first principal component (PC) determining both leaf growth and PSII efficiency. In contrast, the ratio ACC/ABA was negatively correlated with leaf biomass. Although the underlying physiological mechanisms by which rootstocks mediate leaf area or chlorophyll fluorescence (and thus influence tomato salt tolerance) seem complex, a putative potassium–CK interaction involved in regulating both processes merits further attention.     

Cowpea aphid (Aphis craccivora) associated with different host plants has different facultative endosymbionts

Maternally inherited facultative endosymbiotic bacteria are common among insects, including many polyphagous insect herbivores. To investigate whether symbiont infection is structured by host plant in the polyphagous aphid Aphis craccivora Koch, pyrosequencing and diagnostic PCR were performed on 26 populations from two different host plants, alfalfa (Medicago sativa) or black locust (Robinia pseudoacacia). Results indicated that Aphis craccivora harbours distinctly different microbial communities in alfalfa versus locust. The facultative symbiont Hamiltonella was found only in aphids collected from alfalfa, and the facultative symbiont Arsenophonus was found only in aphids from locust. Hamiltonella is known to protect aphids against hymenopteran parasitoids, whereas the phenotypic effects of Arsenophonus in aphids are unknown. Correspondingly, a screen of the aphid samples for hymenopteran DNA indicated that Hamiltonella‐bearing alfalfa populations of A. craccivora experienced lower parasitism than Arsenophonus‐bearing locust populations. This study contributes to the growing body of evidence that correlative associations between bacterial endosymbionts and host plants may be a common phenomenon in polyphagous herbivores, and suggests that microbial symbionts have the potential to act as drivers for observed ecological differences among host‐associated populations of polyphagous insects.     

OSTEOBLASTIC CELLS FROM RAT LONG BONE II: ADHESION TO SUBSTRATA AND INTEGRIN EXPRESSION IN PRIMARY AND PROPAGATED CULTURES

Propagation in vitro of rat tibial osteoblasts (ROB) is accompanied by increased expression of the early osteogenic marker alkaline phosphatase (AP) and maturation of the osteogenic phenotype. In order to establish the pattern of the integrin expressed in ROB during progression to the mature osteoblastic phenotype, we have used biosynthetic, immunoblotting and immuno-histochemical assays. We immunoprecipitated from osteoblasts, expanded for 1.5- and 7.5-doubling, α5β1, αvβ3, α3β1, α6β1 and α1β1 integrin heterodimers; furthermore β5, α2 and α4 chains were detected by immunoblots and indirect immunofluorescence. αv, α1, α6 subunits in most cells, and β3 and β1 subunits in a minority, were found to be associated with adhesion plaques in osteoblasts of 1.5-, 4.5- and 7.5-doubling grown in the presence of FCS, while all other subunits stained diffusely all the cells. Adhesion to fibronectin (FN), laminin (LN), collagen type I (COL I) and III (COL III) by ROB at different doubling (1.5–11) was dependent on substratum concentration, and after 2.5h at 55nm 60% of the cells adhered to all substrata. Arg-Gly-Asp-Ser (RGDS) containing peptides inhibited adhesion of cells differentially, according to substratum; no dependence on extent of progation in vitro was observed. In conclusion, ROB cultured in vitro for 1.5- to 11-doubling had an unchanged pattern of expression of integrin subunits, heterodimer association and cellular distribution. Adhesion specificity and affinity were also unchanged. These results suggest that the phenotypic maturation, detected as an increase in AP expression, is not accompanied by major changes in the potential for cell—matrix interactions, and does not correspond to changes in the type of integrin subunits expressed by osteoblasts.     

CONSUMERS REPORT PREFERENCES WHEN THEY SHOULD NOT: A CROSS-CULTURAL STUDY

If a chi‐squared analysis were to be performed to determine whether preferences were significant in a paired preference test, the appropriate expected frequencies in the analysis would represent those that would occur should the consumers have no preference. One way of determining these ‘no preference’frequencies, for a particular test situation, would be to note the preference responses obtained when the stimuli were putatively identical. Over 2000 consumers were given paired preference tests in which the stimuli were putatively identical. Response conditions and consumer groups were varied and the proportions of preference and no preference responses were noted. In a preliminary experiment, further research was seen to be justified when for putatively identical stimuli, judges did not exclusively express lack of preference; many expressed a preference for one or other of the stimuli. Further experiments were conducted using a written response condition and putatively identical potato chips (potato crisps) as stimuli. Using a single ‘no preference’option, variation in the placement of this option at either first, second or third place on the response sheet had no significant effect on the response frequencies. The proportion of ‘no preference’responses was approximately 30% in all cases. A previously reported 40‐20‐40 distribution was not always confirmed. The experiment was repeated with Korean consumers; these had fewer ‘no preference’responses. Deriving preferences from hedonic scales, rather than having judges respond to preference options, increased the proportion of ‘no preference’responses, with American judges still having more than Korean judges. Yet there are logical objections to extracting preference data from hedonic scales. Increasing the number of ‘no preference’options to two or three, had the effect of increasing the number of ‘no preference’responses up to as much as approximately 60%. Extending the results to Koreans, using two ‘no preference’options, it was seen that only the judges in an anonymous response condition had significantly fewer ‘no preference’responses than Americans. The use of these response frequencies as expected frequencies in chi squared analyses was illustrated, after adjustments for counterbalancing.     

The allopolyploid origin of Narcissus obsoletus (Alliaceae): identification of parental genomes by karyotype characterization and genomic in situ hybridization

Karyological and genomic in situ hybridization (GISH) approaches provided evidence of the parentage and origin of the hybrid species Narcissus obsoletus. Here, we demonstrate that the putative parental species, N. serotinus L. and N. elegans (Haw.) Spach, recently proposed because of their intermediate morphological traits, have participated in the hybridization process forming this taxon. Karyotype characterization of parental genomes in populations from S Spain and N Morocco has revealed differences in chromosome length and karyotype asymmetry, highlighting their diploid nature. Multicolour GISH on metaphase plates of N. obsoletus, with N. serotinus and N. elegans DNA used as probes, showed differential fluorescent staining of 10 and 20 chromosomes from parental genomes, respectively. Both parental genomes were detected in the allopolyploid, albeit in a duplicated manner. Secondary hybridization between N. obsoletus and N. serotinus was also detected karyologically. Little karyological differentiation between different geographic regions was found in either N. serotinus or N. obsoletus. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 477–498.     

Phylogenetic relationships of a new genus and species of microteiid lizard from the Atlantic forest of north-eastern Brazil (Squamata, Gymnophthalmidae)

A new genus and species of a short limbed and slightly elongate gymnophthalmid lizard is described from the Atlantic rain forests of north-eastern Brazil. The new genus is also characterized by short and stout pentadactyl limbs, presence of prefrontals, absence of frontoparietals, distinctive ear opening and eyelid, two pairs of genials, a distinct collar, smooth, quadrangular, dorsal scales, quadrangular ventrals, fused postfrontal and postorbital bones, and two pairs of sternal ribs. The geographical distribution of the new taxon extends from the state of Rio Grande do Norte to the northern bank of the Rio São Francisco in the state of Alagoas. All specimens were obtained in leaf litter, an observation which agrees with the fossorial habits suggested by the body shape and massive aspect of the head of this species. A phylogenetic analysis based on external morphology, osteology, and molecular data recovered the new lizard as the sister genus to Anotosaura , and Colobosauroides as the sister group to these two.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 543−557.     

Positive effect of shredders on microbial biomass and decomposition in stream microcosms

1. Animals play a major role in nutrient cycling via excretory processes. Although the positive indirect effects of grazers on periphytic algae are well understood, little is known about top‐down effects on decomposers of shredders living on leaf litter. 2. Nutrient cycling by shredders in oligotrophic forest streams may be important for the microbial‐detritus compartment at very small spatial scales (i.e. within the leaf packs in which shredders feed). We hypothesised that insect excretion may cause local nutrient enrichment, so that microorganism growth on leaves is stimulated. 3. We first tested the effect of increasing concentration of ammonium (+10, +20 and +40 μg NH₄⁺ L^?1) on fungal and bacterial biomass on leaf litter in a laboratory experiment. Then we performed two experiments to test the effect of the presence and feeding activity of shredder larvae. We used two species belonging to the trichopteran family Sericostomatidae: the Palaearctic Sericostoma vittatum and the Neotropical Myothrichia murina, to test the effect of these shredders on fungal and bacterial biomass and decomposition on leaves of Quercus robur and Nothofagus pumilio, respectively. All experiments were run in water with low ammonium concentrations (2.4 ± 0.34 to 14.47 ± 0.95 μg NH₄⁺ L^?1). 4. After 5 days of incubation, NH₄ concentrations were reduced to near‐ambient streamwater concentrations in all treatments with leaves. Fungal biomass was positively affected by increased ammonium concentration. On the other hand, bacteria abundance was similar in all treatments, both in terms of abundance (bacteria cells mg^?1 leaf DW) and biomass. However, there was a tendency towards larger mean cell size in treatments with 20 μg NH₄ L^?1. 5. In the experiment with S. vittatum, fungal biomass in the treatment with insects was more than twice that in the control after 15 days. Bacteria were not detected in treatments with insects, where hyphae were abundant, but they were abundant in treatments without larvae. In the decomposition experiment run with M. murina, leaf‐mass loss was significantly higher in treatments with larvae than in controls. 6. Our hypothesis of a positive effect of shredders on fungal biomass and decomposition was demonstrated. Insect excretion caused ammonium concentration to increase in the microcosms, contributing to microbial N uptake in leaf substrata, which resulted in structural and functional changes in community attributes. The positive effect of detritivores on microbes has been mostly neglected in stream nutrient‐cycling models; our findings suggest that this phenomenon may be of greater importance than expected in stream nutrient budgets.