Environmental variability and the initiation of dispersal: turbulence strongly increases seed release. (1/10)

Dispersal is a critical process in ecology. It is an important biological driver of, for example, invasions, metapopulation dynamics, spatial pattern formation and pathogen movement. Much is known about the effect of environmental variability, including turbulence, on dispersal of diaspores. Here, we document experimentally the strong but under-explored influence of turbulence on the initiation of dispersal. Flower heads of two thistle species (Carduus nutans and Carduus acanthoides) with ripe seeds were exposed to series of laminar and turbulent air flows of increasing velocity in a wind tunnel. Seed release increased with wind speeds for both laminar and turbulent flows for both species. However, far more seeds were released, at significantly lower wind speeds, during turbulent flows. These results strongly suggest a need for more quantitative studies of abscission in the field, as well as dispersal models that incorporate variability in the diaspore release phase.  (+info)

Seed release by invasive thistles: the impact of plant and environmental factors. (2/10)

Dispersal is a key process in biological studies of spatial dynamics, but the initiation of dispersal has often been neglected, despite strong indications that differential timing of dispersal can significantly affect dispersal distances. To investigate which plant and environmental factors determine the release of plumed seeds by the invasive thistles Carduus acanthoides and Carduus nutans, we exposed 192 flower heads of each species to increasing wind speeds in a full-factorial wind tunnel experiment with four air flow turbulence, three flower head wetness and two flower head temperature levels. The number of seed releases was highest under dry and turbulent conditions and from heads that had already lost a considerable number of seeds, but was not affected by flower head size, head angle or temperature. Inspection of the trials on video showed that higher wind speeds were needed to meet the seed release threshold in laminar flows and for C. acanthoides heads that had been wet for a longer time. Species differences were minimal, although seed release was more sensitive to lower levels of turbulence in the larger-headed and more open C. nutans heads. Knowledge of seed release biases towards weather conditions favourable for long-distance dispersal improves our understanding of the spread of invaders and allows managers to increase the efficiency of their containment strategies by applying them at crucial times.  (+info)

Leaf-cutting ant nests near roads increase fitness of exotic plant species in natural protected areas. (3/10)

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Evolution of flowering decisions in a stochastic, density-dependent environment. (4/10)

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Counting pollen grains using readily available, free image processing and analysis software. (5/10)

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Integrating multiple disturbance aspects: management of an invasive thistle, Carduus nutans. (6/10)

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Bottom-up effects may not reach the top: the influence of ant-aphid interactions on the spread of soil disturbances through trophic chains. (7/10)

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Protection of apigenin against kainate-induced excitotoxicity by anti-oxidative effects. (8/10)

Apigenin (5,7,4'-trihydroxyflavone) is a principal ingredient of Cirsium japonicum. These experiments were performed to determine whether apigenin has neuroprotective effects against kainic acid (KA)-induced excitotoxicity in vitro and in vivo. Intraperitoneal (i.p.) administration of apigenin (25, 50 mg/kg) decreased the seizure scores induced by KA injection (40 mg/kg, i.p.) in mice. In addition, the convulsion onset time was significantly delayed by apigenin administration. Moreover, we found that apigenin blocked KA-induced seizure-form electroencephalogram (EEG) discharge activity in the brain cortex. In hippocampal cells, apigenin inhibited KA-induced excitotoxicity in a dose-dependent manner as measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. To study the possible mechanisms underlying the in vitro neuroprotective effects of apigenin against KA-induced cytotoxicity, we also examined the effect of apigenin on intracellular reactive oxygen species (ROS) elevations in cultured hippocampal neurons and found that apigenin treatment dose-dependently inhibited intracellular ROS elevation. The remarkable reduction of glutathione (GSH) levels induced by KA in hippocampal tissues was reversed by apigenin in a dose-dependent manner. In addition, similar results were obtained after pretreatment with free radical scavengers such as trolox and dimethylthiourea (DMTU). Finally, after confirming the protective effect of apigenin in hippocampal CA3 region, we found apigenin is an active compound in KA-induced neuroprotection. These results collectively indicate that apigenin alleviates KA-induced excitotoxicity by quenching ROS as well as inhibiting GSH depletion in hippocampal neurons.  (+info)

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