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This field study with the C3 bromeliad Vriesea sanguinolenta (Cogn. & Marchal 1874) was initiated to explore the importance of size‐related ecophysiological changes in vascular epiphytes in a natural tropical setting. In this species, a step change from atmospheric to tank‐forming life form occurs during early ontogeny, followed by a continuous size increase of individuals with water‐impounding tanks. Although our study focused on the water‐impounding phase, this growth pattern also allowed us to compare ecophysiological consequences of a step change in life form with those associated with size increments among plants of identical life form. The shift in life form was accompanied by relatively minor changes, for example in leaf morphology (decrease in leaf thickness and trichome density) and leaf physiology (decrease in photosynthetic capacity), while there were more substantial changes during the tank‐forming phase. A major trend was a decreasing dependence of larger plants on internally stored water due to a more efficient tank. We suggest that the resulting, more reliable water supply in larger plants may be the proximate cause for the observed size‐related differences in leaf anatomy (relative reduction of water storage tissue, and relative and absolute increase in chlorenchyma thickness), leaf morphology (increase in stomatal density, decrease in trichome density), and leaf physiology (increase in net rates of CO2 uptake, more conservative stomatal behaviour, higher residual transpiration). The results are compared with previous studies on heteroblasty in bromeliads, but are also discussed in the context of a gradual shift from a drought‐tolerance to a drought‐avoidance strategy.  相似文献   
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咬合力作为衡量动物生存能力的重要指标,可以在一定程度上反映动物捕食、反捕食和争夺配偶的能力。对于蜥蜴类动物而言,头部形态和咬合力大小之间常呈现显著线性关系。通过测量2018年7月采集于新疆霍城县图开沙漠的24号草原蜥(Trapelussanguinolenta)(雌13,雄11)的头部形态指标,并使用薄膜压力测试仪测定咬合力,采用单因素方差分析(ANOVA)、主成分分析、模型拟合及逐步回归4种方法探究草原蜥咬合力的两性差异及其与头部形态指标的关系。结果表明,草原蜥头体长、头长、头宽、头高、口宽和下颌长在两性个体间均无显著差异,草原蜥两性个体之间咬合力也没有显著差异。主成分分析及赤池信息模型拟合结果均显示,头长、头宽和下颌长是影响草原蜥咬合力的重要因素,逐步回归分析揭示草原蜥的咬合力主要受头宽影响。上述研究结果表明,草原蜥的咬合力受头部形态大小的影响,但两性个体之间咬合力却不存在显著差异,这与头部形态特征未表现出两性差异一致,这可能是草原蜥对灌丛生活的适应,具体而言,是头部大小与运动权衡的结果。  相似文献   
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Zotz G  Richter A 《Annals of botany》2006,97(5):745-754
BACKGROUND AND AIMS: This study examined the physiological basis of the cost of reproduction in the epiphytic bromeliad Werauhia sanguinolenta, growing in situ in a tropical lowland forest in Panama. METHODS: Entire mature plants were sampled repeatedly over the course of 2 years, which represents the common interval between reproductive events. Due to the uncertainty concerning the appropriate currency of resource allocation to reproduction, the temporal changes of the contents of total non-structural carbohydrates (TNC) and of all major nutrient elements in different plant parts were studied (stems, green leaves, non-green leaf bases, roots and reproductive structures when present). KEY RESULTS: Although TNC varied with time in all compartments, this variation was more related to seasonal fluctuations than to reproductive status. The contents of the nutrient elements, N, P, K, Mg and S, on the other hand, showed significant differences between reproductive and non-reproductive individuals, while Ca did not change with reproductive status. Differences in nutrient contents were most pronounced in stems. Seeds were particularly enriched in P, much less so in N and the other nutrient elements. Model calculations of nutrient fluxes indicate that a plant needs about 2 years to accumulate the amount of P invested in a fruit crop, while the estimated uptake rates for N were much faster. CONCLUSIONS: Since most mature individuals of this species fruit every other year, it is hypothesized that P is the prime limiting factor for reproduction. These findings therefore add to an increasing body of evidence that P rather than N is limiting growth and reproduction in vascular epiphytes.  相似文献   
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This study addresses the question of how size-related changes in leaf morphology and physiology influence light absorption and carbon gain of the epiphytic bromeliad Vriesea sanguinolenta. A geometrically based computer model, Y-plant, was used for the three-dimensional reconstruction of entire plants and for calculation of whole plant light interception and carbon gain. Plants of different sizes were reconstructed, and morphological and physiological attributes of young and old leaves, and small and large plants were combined to examine the individual effects of each factor on light absorption and carbon gain of the plant. The influence of phyllotaxis on light absorption was also explored. Departure of measured divergence angles between successive leaves from the ideal 137.5 degrees slightly decreased light absorption. The only morphological parameter that consistently changed with plant size was leaf shape: larger plants produced more slender foliage, which substantially reduced self-shading. Nevertheless, self-shading increased with plant size. While the maximum rate of net CO(2) uptake of leaves increased linearly with plant size by a factor of two from the smallest to the largest individual, the potential plant carbon gain (based on total foliage area) showed a curvilinear relationship, but with similar numerical variation. We conclude that leaf physiology has a greater impact on plant carbon gain than leaf and plant morphology in this epiphytic bromeliad.  相似文献   
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Based primarily on internal anatomy,the genus Agama(sensu lato)of Agamidae was subdivided into six genera:Agama,Laudakia,Trapelus,Pseudotrapelus,Brachysaura,and Xenagama[1,2].  相似文献   
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In insects, a sexual size dimorphism commonly occurs, with larger females. However, as a deviation from this general rule, larger males are found in some species. In these species often sexual selection for large males has been presumed. The spittlebug Cercopis sanguinolenta exhibits a distinct sexual size dimorphism with larger males. Mating behaviour was studied in a field population in respect to mating success of males and females. The aim of this study was to examine the mechanisms that lead to the observed non-random mating pattern. The results showed a mating pattern without size-assortative mating. A correlation was found between mating success and body size in males. In females no such correlation was found. The mobility of males depends on their body size and mobility is high only when females are present. However, in an analysis of covariance it was found that male mating success is not correlated with mobility, when controlled for body size. The mating system of the spittlebug was classified as scramble competition polygyny. Electronic Publication  相似文献   
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