Setting-up tension in the style of Marantaceae

The Marantaceae stand out from other plant families through their unique style movement which is combined with a highly derived form of secondary pollen presentation. Although known for a long time, the mechanism underlying the movement is not yet understood. In this paper, we report an investigation into the biomechanical principles of this movement. For the first time we experimentally confirm that, in Maranta noctiflora, longitudinal growth of the maturing style within the 'straitjacket' of the hooded staminode involves both arresting of the style before tripping and building up of potential for the movement. The longer the style grows in relation to the enclosing hooded staminode, the more does its capacity for curling increase. We distinguish between the basic tension that a growing style builds up normally, even when the hooded staminode is removed beforehand, and the induced tension which comes about only under the pressure of a too short hooded staminode and which enables the movement. The results of our investigations are discussed in relation to previous interpretations, ranging from biomechanical to electrophysiological mechanisms.     

Epizoochory by large herbivores: merging data with models

The dispersal of plant seeds in the fur of large herbivores (epizoochory) is an important but complex long-distance dispersal mechanism. We developed a spatially explicit simulation model of epizoochorous seed dispersal, which was parameterized based on empirical studies of the movement and behaviour of donkeys, and the distribution, seed production, seed accessibility, seed adhesion, and seed retention on donkey fur of selected plant species in a coastal dune nature reserve in Flanders, Belgium. We compared predicted and observed seed numbers of the 14 plant species on donkey fur.

Modelled seed shadows indicate that for most species about half of all seeds dispersed by donkeys should travel a net distance of >100 m, and about 1% should travel >500 m within this more or less isodiametric 100 ha nature reserve. Seeds with longer retention times are expected to travel further than those with short retention times. Enlarging the reserve area had little impact on the forecasted dispersal distances.

Variation among plant species in the observed seed numbers found on donkey fur were well predicted by the model (R²=0.56, P=0.002), though the predictions relied on relatively crude estimates of seed production and accessibility to donkeys, indicating that more accurate estimates of these parameters are needed.

Our model confirms the important role of epizoochory in affecting long-distance seed dispersal, and provides a modelling framework for integrating the multiple components of the dispersal process.     

Movement of adult pecan weevils Curculio caryae within pecan orchards

1 The pecan weevil Curculio caryae (Horn) (Coleoptera: Curculionidae) is an indigenous pest of pecan Carya illinoinensis (Wangenh.) K. Koch, in North America. Understanding the movement of this pest from the orchard floor to host trees could lead to pest management practices that exploit weevil behaviour and thus reduce insecticide application to the entire orchard canopy. Furthermore, no information exists on diel periodicity of pecan weevil movement. 2 Movement of adult pecan weevils crawling and flying to the host trunk, flying to the host canopy, crawling within the host canopy and flying between host trees was studied using four types of passive traps over four seasons. Each type of trap was used to capture weevils at different locations on or near the tree and to discriminate flying versus crawling behaviour. 3 More pecan weevils crawl to the trunk than fly and a proportion of the population flies directly from the orchard floor into the pecan canopy. The majority of this movement occurs at dusk. 4 The vertical distribution of weevils was generally uniform throughout the canopy but more weevils were captured in suspended traps nearest tree tops, rather than traps near the ground, when flying between trees and this was significantly so for two of 4 years. 5 The results of the present study are contrary to previous reports suggesting that most adult pecan weevils fly to the pecan trunk after emergence from the soil; however, our results did indicate that a proportion of the population flies directly from the orchard floor into the pecan canopy and thus would circumvent strategies that attempt to control weevils moving up the trunk.     

Oxygen isotope fractionation between human phosphate and water revisited

The oxygen isotope composition of human phosphatic tissues (δ¹⁸O_P) has great potential for reconstructing climate and population migration, but this technique has not been applied to early human evolution. To facilitate this application we analyzed δ¹⁸O_P values of modern human teeth collected at 12 sites located at latitudes ranging from 4°N to 70°N together with the corresponding oxygen composition of tap waters (δ¹⁸O_W) from these areas. In addition, the δ¹⁸O of some raw and boiled foods were determined and simple mass balance calculations were performed to investigate the impact of solid food consumption on the oxygen isotope composition of the total ingested water (drinking water + solid food water). The results, along with those from three, smaller published data sets, can be considered as random estimates of a unique δ¹⁸O_W/δ¹⁸O_P linear relationship: δ¹⁸O_W = 1.54(±0.09) × δ¹⁸O_P−33.72(±1.51) (R² = 0.87: p [H₀:R² = 0] = 2 × 10⁻¹⁹). The δ¹⁸O of cooked food is higher than that of the drinking water. As a consequence, in a modern diet the δ¹⁸O of ingested water is +1.05 to 1.2‰ higher than that of drinking water in the area. In meat-dominated and cereal-free diets, which may have been the diets of some of our early ancestors, the shift is a little higher and the application of the regression equation would slightly overestimate δ¹⁸O_W in these cases.     

Animal movement in dynamic landscapes: interaction between behavioural strategies and resource distributions

Most ecological and evolutionary processes are thought to critically depend on dispersal and individual movement but there is little empirical information on the movement strategies used by animals to find resources. In particular, it is unclear whether behavioural variation exists at all scales, or whether behavioural decisions are primarily made at small spatial scales and thus broad-scale patterns of movement simply reflect underlying resource distributions. We evaluated animal movement responses to variable resource distributions using the grey teal (Anas gracilis) in agricultural and desert landscapes in Australia as a model system. Birds in the two landscapes differed in the fractal dimension of their movement paths, with teal in the desert landscape moving less tortuously overall than their counterparts in the agricultural landscape. However, the most striking result was the high levels of individual variability in movement strategies, with different animals exhibiting different responses to the same resources. Teal in the agricultural basin moved with both high and low tortuosity, while teal in the desert basin primarily moved using low levels of tortuosity. These results call into question the idea that broad-scale movement patterns simply reflect underlying resource distributions, and suggest that movement responses in some animals may be behaviourally complex regardless of the spatial scale over which movement occurs.     

A plastid protein crucial for Ca2+-regulated stomatal responses

* Guard cell movements are regulated by environmental cues including, for example, elevations in extracellular Ca(2+) concentration. Here, the subcellular localization and physiological function of the Ca(2+)-sensing receptor (CAS) protein was investigated. * CAS protein localization was ascertained by microscopic analyses of green fluorescent protein (GFP) fusion proteins and biochemical fractionation assays. Comparative guard cell movement investigations were performed in wild-type and cas loss-of-function mutant lines of Arabidopsis thaliana. Cytoplasmic Ca(2+) dynamics were addressed in plants expressing the yellow cameleon reporter protein YC3.6. * This study identified CAS as a chloroplast-localized protein that is crucial for proper stomatal regulation in response to elevations of external Ca(2+). CAS fulfils this role through modulation of the cytoplasmic Ca(2+) concentration. * This work reveals a novel role of the chloroplast in cellular Ca(2+) signal transduction.     

Phase Segregation Enhanced Ion Movement in Efficient Inorganic CsPbIBr2 Solar Cells

Organic–inorganic hybrid perovskite solar cells with mixed cations and mixed halides have achieved impressive power conversion efficiency of up to 22.1%. Phase segregation due to the mixed compositions has attracted wide concerns, and their nature and origin are still unclear. Some very useful analytical techniques are controversial in microstructural and chemical analyses due to electron beam‐induced damage to the “soft” hybrid perovskite materials. In this study photoluminescence, cathodoluminescence, and transmission electron microscopy are used to study charge carrier recombination and retrieve crystallographic and compositional information for all‐inorganic CsPbIBr₂ films on the nanoscale. It is found that under light and electron beam illumination, “iodide‐rich” CsPbI_{(1+x )}Br_{(2?x )} phases form at grain boundaries as well as segregate as clusters inside the film. Phase segregation generates a high density of mobile ions moving along grain boundaries as ion migration “highways.” Finally, these mobile ions can pile up at the perovskite/TiO₂ interface resulting in formation of larger injection barriers, hampering electron extraction and leading to strong current density–voltage hysteresis in the polycrystalline perovskite solar cells. This explains why the planar CsPbIBr₂ solar cells exhibit significant hysteresis in efficiency measurements, showing an efficiency of up to 8.02% in the reverse scan and a reduced efficiency of 4.02% in the forward scan, and giving a stabilized efficiency of 6.07%.     

Computational and clinical investigation on the role of mechanical vibration on orthodontic tooth movement

The aim of this study is to investigate the biomechanics for orthodontic tooth movement (OTM) subjected to concurrent single-tooth vibration (50 Hz) with conventional orthodontic force application, via a clinical study and computational simulation. Thirteen patients were recruited in the clinical study, which involved distal retraction of maxillary canines with 1.5 N (150 g) force for 12 weeks. In a split mouth study, vibration and non-vibration sides were randomly assigned to each subject. Vibration of 50 Hz, of approximately 0.2 N (20 g) of magnitude, was applied on the buccal surface of maxillary canine for the vibration group. A mode-based steady-state dynamic finite element analysis (FEA) was conducted based on an anatomically detailed model, complying with the clinical protocol. Both the amounts of space closure and canine distalization of the vibration group were significantly higher than those of the control group, as measured intra-orally or on models (p < 0.05). Therefore it is indicated that a 50 Hz and 20 g single-tooth vibration can accelerate maxillary canine retraction. The volume-average hydrostatic stress (VHS) in the periodontal ligament (PDL) was computationally calculated to be higher with vibration compared with the control group for maxillary teeth and for both linguo-buccal and mesial-distal directions. An increase in vibratory frequency further amplified the PDL response before reaching a local natural frequency. An amplification of PDL response was also shown to be induced by vibration based on computational simulation. The vibration-enhanced OTM can be described by mild, vigorous and diminishing zones among which the mild zone is considered to be clinically beneficial.     

How the microstructure of dentine can contribute to reconstructing developing dentitions and the lives of hominoids and hominins

Accounts of dentine microstructure are less well established in the primate life history literature than those of enamel microstructure. The aim of this paper is to draw some basic comparisons between enamel and dentine, but at the same time to show how dentine microstructure can make a major but different contribution to reconstructing past lives than enamel can. Dentine has both an organic and an inorganic component. The organic component contains growth factors, stable isotopes and DNA that survive long after death. The mineral component contains trace elements and preserves an incremental record of tooth growth. These can be used to put a time scale to many past events when the chemistry or microstructure of dentine has become altered during tooth growth. Dentine microstructure allows us to reconstruct tooth root growth in the past and has contributed to a fuller understanding of the modular nature of developing dentitions among hominoids and hominins.