Oviposition response of Simulium reptans (Diptera: Simuliidae) to the presence of conspecific eggs

Abstract.

• 1 The oviposition behaviour of Simulium reptans L. is described from two sites on the River Spey, Scotland. Female aggregations were observed immediately downstream of oviposition sites and were composed mainly of gravid flies (range 60–80%0) together with smaller numbers that were either freshly bloodfed (range 2–17%) or infected with mermithid nematodes (range 0–30%).
• 2 The time from landing on the oviposition sites to the onset of oviposition was recorded. The time in the presence of greater than 1-day-old eggs did not significantly differ from sites with no eggs present. However, the presence of freshly laid or I-day-old eggs significantly shortened the time to onset of oviposition. The cues that elicit oviposition are unknown but it is speculated that they may involve a pheromone.

     

Studies on graft unions

Summary The occurrence of plasmodesmata in the graft interfaces of two heteroplastic grafts (Impatiens walleriana onImpatiens olivieri andHelianthus annum onVicia faba) has been studied. For both systems two types of intercellular strand are described: 1. Continuous plasmodesmata interconnecting the cells of stock and scion and 2. half plasmodesmata traversing the wall part of one partner cell without connection to the abutting cell. Single strands or branched forms occur in both types of plasmodesma. In the case of half plasmodesmata, branchings with extended median nodules predominate. The distribution of half and continuous plasmodesmata varies with the different areas of a graft interface: in the region of bridging vascular tissues most cell connections are continuous. In areas where cortex or pith-derived callus cells and those of misaligned tissues (cortex/vascular tissue; cortex/pith; pith/vascular tissue) match, discontinuous strands predominate.Branched half plasmodesmata also occur in presumably fused walls between related callus cells; they are typical structures secondarily formed in non-division walls.The results are discussed with regard to compatibility/incompatibility phenomena in heterografts and the development and function of interspecific cell bridges.     

REACTION NORMS OF MORPHOLOGICAL AND LIFE-HISTORY TRAITS TO LIGHT AVAILABILITY IN IMPATIENS CAPENSIS

For plants, light availability is an important environmental factor that varies both within and between populations. Although the existence of sun and shade “ecotypes” is controversial, it is often assumed that trade-offs may exist between performance in sun and in shade. This study therefore investigated variation in reaction norms to light availability within and between two neighboring natural populations of the annual Impatiens capensis, one in full sun and the other in a forest understory. Seedlings were collected randomly from both populations and grown to maturity in a greenhouse under two light conditions: full light and 18% of full light. Selfed full-sib seed families were collected from plants from both populations grown in both parental light environments. To characterize family reaction norms, seedlings from each family were divided into the same two light treatments and individuals were scored for a variety of morphological and life-history traits. The maternal light environment had little impact on progeny reaction norms. However, the two study populations differed both qualitatively and quantitatively in plastic response to light availability (indicated by significant population x environment interactions in mixed-model ANCOVA). Much of this difference was attributable to population differences in light sensitivity of axillary meristem allocation patterns, which produced concurrent differences in reaction norms for a suite of developmentally linked traits. Within each population, different sets of traits displayed significant variation in plasticity (indicated by significant family x environment interactions). Thus, the genetic potential for evolutionary response to selection in heterogeneous light environments may differ dramatically between neighboring plant populations. Between-environment genetic correlations were largely positive in the woods population and positive or nonsignificant in the sun population; there was no evidence for performance trade-offs across environments or sun or shade “specialist” genotypes within either population. There was little evidence that population differences represented adaptive differentiation for sun or shade; rather, the results suggested the hypothesis of differential selection on patterns of meristem allocation caused by population differences in timing of mortality and intensity of competition.     

聚苯乙烯纳米塑料-植物蛋白冠的形成与特征

为探究聚苯乙烯纳米塑料-植物蛋白冠的形成过程以及蛋白冠的形成对植物可能造成的影响,本研究选用3种平均粒径为200nm不同表面修饰的聚苯乙烯纳米塑料微球和新几内亚凤仙(Impatiens hawkeri)为对象,将3种聚苯乙烯纳米塑料分别与新几内亚凤仙的叶蛋白提取物进行反应,反应时间分别为2、4、8、16、24、36 h。利用扫描电镜(scanning electron microscopy, SEM)观察其形貌变化,原子力显微镜(atomic force microscopy, AFM)进行表面粗糙度测定,使用纳米粒度和zeta电位分析仪测定水合粒径及zeta电位,液相色谱-串联质谱(liquid chromatography-tandem mass spectrometry, LC-MS/MS)鉴定蛋白冠的蛋白成分。从生物学过程、细胞组分以及分子功能3个方面对蛋白进行分类,研究不同表面修饰的纳米塑料对蛋白的吸附选择,探究聚苯乙烯纳米塑料-植物蛋白冠的形成与特征,预测蛋白冠对植物造成的可能影响。结果表明：随着反应时间增加,纳米塑料的形貌变化越发明显,表现为尺寸和粗糙度的增加和稳定性的增...     

The anthocyanidins of some new guinea impatiens

17 strains of New Guinea Impatiens belonging to the I. schlecteri—linearifolia group and to the I. hawkeri—mooreana—nivea group were analysed for the anthocyanidin pigments. Pelargonidin predominated in the schlecteri group white malvidin was most common in the mooreana group.     

Influence of different Inocula of Meloidogyne arenaria on plant growth parameters and nematode multiplication in balsam (Impatiens balsamina)

Pathogenic effect of root-knot nematode Meloidogyne arenaria was studied on balsam (Impatiens balsamina) by inoculating the different inoculum levels of root-knot nematode. It was observed that the inoculum levels up to 2000 J₂ of root-knot nematode did not show significant reduction in plant growth characters as compared to control. Although the significant reduction in plant growth characters was recorded at and above 3000 J₂ of root-knot nematode, progressive increase in the host infestation as indicated by the number of galls as well as the population of root-knot nematode was recorded with an increase in the level of inoculum. However, the rate of nematode multiplication was reduced with the increase in the inoculum density of M. arenaria. It can be concluded from these results that the damaging threshold level of M. arenaria on balsam was found to be as 3000 J₂/plant.     

Trade-offs between flower number and investment to a flower in selfing and outcrossing varieties of Impatiens hypophylla (Balsaminaceae)

Floral resource allocation was compared on a whole-plant basis between two varieties of Impatiens hypophylla that differ in flower size. There were significant negative correlations between flower number and investments to a flower at both the within-population and between-variety levels. In individual flowers, var. hypophylla with larger flowers invested significantly more resources to male and pollinator-attractive functions, whereas investments to female function did not differ between the varieties. In experimental populations placed in the field, pollinators preferred the larger flowers of var. hypophylla even within the same habitat of var. microhypophylla, which has smaller flowers. There was a significant lack of observed heterozygosity only in var. microhypophylla. Thus, the outcrossing variety had more attractive but fewer flowers, while the selfing variety had less attractive but more abundant flowers.     

Reducing environmental bias when measuring natural selection

Abstract.— Crucial to understanding the process of natural selection is characterizing phenotypic selection. Measures of phenotypic selection can be biased by environmental variation among individuals that causes a spurious correlation between a trait and fitness. One solution is analyzing genotypic data, rather than phenotypic data. Genotypic data, however, are difficult to gather, can be gathered from few species, and typically have low statistical power. Environmental correlations may act through traits other than through fitness itself. A path analytic framework, which includes measures of such traits, may reduce environmental bias in estimates of selection coefficients. We tested the efficacy of path analysis to reduce bias by re-analyzing three experiments where both phenotypic and genotypic data were available. All three consisted of plant species (Impatiens capensis, Arabidopsis thaliana , and Raphanus sativus) grown in experimental plots or the greenhouse. We found that selection coefficients estimated by path analysis using phenotypic data were highly correlated with those based on genotypic data with little systematic bias in estimating the strength of selection. Although not a panacea, using path analysis can substantially reduce environmental biases in estimates of selection coefficients. Such confidence in phenotypic selection estimates is critical for progress in the study of natural selection.     

Costs of plasticity in foraging characteristics of the clonal plant Ranunculus reptans

In clonal plants, evolution of plastic foraging by increased lengths of leaves and internodes under unfavourable conditions may be constrained by costs and limits of plasticity. We studied costs and limits of plasticity in foraging characteristics in 102 genotypes of the stoloniferous herb Ranunculus reptans. We grew three replicates of each genotype with and three without competition by the naturally co-occuring grass Agrostis stolonifera. We used regression and correlation analyses to investigate potential costs of plasticity in lengths of leaves and stolon internodes, developmental instability costs of these traits, and a developmental range limit of these traits. We used randomization procedures to control for spurious correlations between parameters calculated from the same data. Under competition the number of rosettes, rooted rosettes, and flowers was 58%, 40%, and 61% lower, respectively, than in the absence of competition. Under competition lengths of leaves and stolon internodes were 14% and 6% smaller, respectively, than in the absence of competition. We detected significant costs of plasticity in stolon internode length in the presence of competition when fitness was measured in terms of the number of rosettes and the number of flowers (selection gradients against plasticity were 0.250 and 0.214, respectively). Within-environment variation (SD) in both foraging traits was not positively correlated with the corresponding plasticity, which indicates that there were no developmental instability costs. More plastic genotypes did not have less extreme trait values than less plastic genotypes for both foraging traits, which indicates that there was no developmental range limit. We conclude that in R. reptans costs of plasticity more strongly constrain evolution of foraging in the horizontal plane (i.e., stolon internode length) than in the vertical plane (i.e., leaf length).     

Simultaneous determination of three naphthoquinones in the leaves of Impatiens balsamina L. by reversed-phase high-performance liquid chromatography

Introduction – Naphthoquinones; lawsone ( 1 ), lawsone methyl ether ( 2 ) and methylene‐3,3′‐bilawsone ( 3 ) are the main active compounds of Impatiens balsamina leaves. Objective – To develop and validate an HPLC method for simultaneous quantitative determination of 1 – 3 in I. balsamina leaf extracts. Methodology – The method utilised a Supelco® C₁₈ column (5 µm, 4.6 × 150 mm) at 25°C with the mixture of 2% aqueous acetic acid : methanol (gradient elution as follows: 0–10 min, 25 : 75; 10–20 min, 32 : 68; 20–35 min, 55 : 45) as the mobile phase at a flow‐rate of 1 mL/min, and UV detection at 280 nm. The parameters of linearity, repeatability, reproducibility, accuracy specificity and sensitivity of the method were evaluated. Results – The recovery of the method was 96–101% and linearity (r² ≥ 0.9995) was obtained for all naphthoquinones. A high degree of specificity, as well as repeatability and reproducibility (RSD less than 5%), were also achieved. Copyright © 2010 John Wiley & Sons, Ltd.