The functional morphology of light capture and carbon gain in the Redwood forest understorey plant Adenocaulon bicolor Hook

1. A three-dimensional geometric simulation model of crown architecture was utilized to investigate the efficiency of light capture and its relationship to whole-plant CO₂ assimilation of Adenocaulon bicolor .
2. Positioning of the leaves by the combined effects of ontogenetic variations in petiole length and angle and leaf size, and the leaf divergence angles were shown to be effective in minimizing self shading. The efficiency of light absorption varied from 0·64 to 0·70 among individual plants that were sampled.
3. Plant to plant variation in simulated daily carbon gain was strongly influenced by variations in the direct and diffuse PFD received by the individual plants. When simulations were run for all plants under a single common light environment, the carbon gain was strongly dependent on the efficiencies of light absorption of the different plants.
4. Simulations in which petiole length was varied showed a non-linear dependence of light absorption efficiency on petiole length. When both petiole length and leaf size were varied in a way that maintained a constant biomass then an optimal petiole length that corresponded to the observed petiole length was apparent. The observed divergence angle between successive leaves also maximized light absorption efficiency as compared to greater or lesser angles, but increases in internode length had no significant effect.
5. The results of this study provide evidence for selection for an 'optimal design' of crown architecture in Adenocaulon bicolor that maximizes light capture.     

Evolutionary Relationships Among the Eukaryotic Crown Taxa Taking into Account Site-to-Site Rate Variation in 18S rRNA

In this study we constructed a bootstrapped distance tree of 500 small subunit ribosomal RNA sequences from organisms belonging to the so-called crown of eukaryote evolution. Taking into account the substitution rate of the individual nucleotides of the rRNA sequence alignment, our results suggest that (1) animals, true fungi, and choanoflagellates share a common origin: The branch joining these taxa is highly supported by bootstrap analysis (bootstrap support [BS] > 90%), (2) stramenopiles and alveolates are sister groups (BS = 75%), (3) within the alveolates, dinoflagellates and apicomplexans share a common ancestor BS > 95%), while in turn they both share a common origin with the ciliates (BS > 80%), and (4) within the stramenopiles, heterokont algae, hyphochytriomycetes, and oomycetes form a monophyletic grouping well supported by bootstrap analysis (BS > 85%), preceded by the well-supported successive divergence of labyrinthulomycetes and bicosoecids. On the other hand, many evolutionary relationships between crown taxa are still obscure on the basis of 18S rRNA. The branching order between the animal-fungal-choanoflagellates clade and the chlorobionts, the alveolates and stramenopiles, red algae, and several smaller groups of organisms remains largely unresolved. When among-site rate variation is not considered, the inferred tree topologies are inferior to those where the substitution rate spectrum for the 18S rRNA is taken into account. This is primarily indicated by the erroneous branching of fast-evolving sequences. Moreover, when different substitution rates among sites are not considered, the animals no longer appear as a monophyletic grouping in most distance trees. Received: 11 June 1997 / Accepted: 21 July 1997     

Nodulation of lucerne (Medicago sativa L.) in an acid soil: pH dynamics in the rhizosphere of seedlings growing in rhizotrons

A lime-pellet around seeds of lucerne significantly increased crown nodulation in an acid soil. To investigate whether neutralization or calcium were of importance when lime was supplied, experiments with plants were done either in pots or in rhizotrons. Crown nodulation was used to quantify the effect of these two parameters.For the neutralization of the soil, KOH (in pots) or K₂CO₃ (in rhizotrons) was added. The crown nodulation of pot-grown plants increased from 31% to 53%. In rhizotrons, the number of crown-nodulated seedlings increased from 9% to 53%. If calcium was supplied additionally (as CaCl₂ or CaSO₄), 63% crown nodulation was found in pots, and 68% in rhizotrons. These numbers are close to the crown nodulation with lime (CaCO₃) alone: 70% in pots and 71% in rhizotrons. In the soil studied, the beneficial effect of lime is largely due to neutralization (80%), and only a minor part (20%) is due to the input of calcium.Using rhizotrons, the dynamics of the pH in the rhizosphere of lime-treated and untreated seedlings was followed during a period of 12 days. It was found that, even in the absence of lime, the pH along the taproot increased from 5.1 to 5.7. However, this did not result in the formation of root nodules. Nodulation was obtained only by adding neutralizing chemicals, which increased the pH during the initial 3 days, the acid sensitive period of the process.     

Photosynthesis in localised regions of oat leaves infected with crown rust (Puccinia coronata): quantitative imaging of chlorophyll fluorescence

Localised changes in photosynthesis in oat leaves infected with the biotrophic rust fungus Puccinia coronata Corda were examined at different stages of disease development by quantitative imaging of chlorophyll fluorescence. Following inoculation of oat leaves with crown rust the rate of whole-leaf gas exchange declined. However, crown rust formed discrete areas of infection which expanded as the disease progressed and these localised regions of infection gave rise to heterogeneous changes in photosynthesis. To quantify these changes, images of chlorophyll fluorescence were taken 5, 8 and 11 d after inoculation and used to calculate images representing two parameters; Φ_II, a measure of PSII photochemical efficiency and ΔFm/Fm′, a measure of non-photochemical energy dissipation (qN). Five days after inoculation, disease symptoms appeared as yellow flecks which were correlated with the extent of the fungal mycelium within the leaf. At this stage, Δ_II was slightly reduced in the infected regions but, in uninfected regions of the leaf, values of Φ_II were similar to those of healthy leaves. In contrast, qN (ΔFm/Fm′) was greatly reduced throughout the infected leaf in comparison to healthy leaves. We suggest that the low value of qN in an infected leaf reflects a high demand for ATP within these leaves. At sporulation, 8 d after inoculation, Φ_II was reduced throughout the infected leaf although the reduction was most marked in areas invaded by fungal mycelium. In the infected leaf the pattern of non-photochemical quenching was complex; qN was low within invaded regions, perhaps reflecting high metabolic activity, but was now much higher in uninfected regions of the infected leaf, in comparison to healthy leaves. Eleven days after inoculation “green islands” formed in regions of the leaf associated with the fungal mycelium. At this stage, photosynthesis was severely inhibited over the entire leaf; however, heterogeneity was still apparent. In the region not invaded by the fungal mycelium, Φ_II and qN were very low and these regions of the leaf were highly fluorescent, indicating that the photosynthetic apparatus was severely damaged. In the greenisland tissue, Φ_II was low but detectable, indicating that some photosynthetic processes were still occurring. Moreover, qN was high and fluorescence low, indicating that the cells in this region were not dead and were capable of significant quenching of chlorophyll fluorescence.     

Brief communication: The use of alternative dental measurements on deciduous teeth

The present study investigates the utility of cervical measurements in deciduous teeth and how they correlate with traditional measurements of the crown. First, this study establishes definitions by which these measurements could reliably be taken. Next, deciduous cervical and traditional crown diameters were taken on three distinct skeletal samples: a Neolithic assemblage from Central Anatolia (Çatalhöyük, n = 85), a precontact sample from Northern California (CA‐ALA‐329, n = 34), and a group of intrusive burials interred at Çatalhöyük that date between AD 60 and 1650 (n = 38). Across the dentition there are positive correlations between crown and cervical measurements, which tend to be higher in anterior teeth than in posterior teeth. Both measurements show low correlations with age; however, cervical measurements show fewer negative correlations with age. An intraobserver error study found low levels of error for both types of measurements. On a subset of the Çatalhöyük sample (n = 9), a principal components and biological distance analysis were conducted comparing the two types of measurements. Also, all three samples were subject to a canonical discriminant function analysis and the results from cervical and crown measurements were compared. All analyses produced slightly different results for each type of data suggesting that crown and cervical measurements capture different aspects of tooth shape. While cervical and crown measurements provide different statistical results, cervical measurements can provide information relevant to anthropological studies and may allow for larger datasets to be used by allowing the inclusion of teeth with modified crowns. Am J Phys Anthropol 149:299–306, 2012. © 2012 Wiley Periodicals, Inc.     

光照条件、植株冠层结构和枝条寿命的关系——以桂花和水杉为例

根据衰老理论的代谢率假说,生物寿命与其代谢率有关,个体大小相同的生物体,在质量较好的微生境中通常比较差生境中具有更高的代谢速率。因此,生物体在资源供给较差的生境中通常比资源供给较充足的生境中具有更长的寿命。枝条是木本植物植冠构建的基本单元之一,如果枝条遵循代谢率假说,则可推测在光照较好环境下的植物枝条或小枝将比其在遮荫环境下具有更短的寿命,即枝条寿命与光照条件成反比。以常绿物种桂花(Osmanthus fragrans)和落叶物种水杉(Metasequoiaglyptostroboides)为研究对象,通过测量不同光照环境下,植株大小(株高和胸径)、冠层深度、冠层轮廓(冠层深度/冠层宽度)、相对冠层宽度(冠层宽度/植株高度)以及植株凋落枝条寿命等性状,探讨了光照条件对成年植株冠层形态结构和植株枝条寿命的影响。调查发现:1)枝条的寿命在遮荫条件下显著高于全光照条件下,与理论预测吻合;2)随遮荫程度增加,植株冠层深度和冠层轮廓增加,相对冠层宽度减小;3)枝条的平均寿命与植株冠层深度和冠层轮廓成正比,与植株相对冠层宽度成反比。这表明光照条件可能通过改变植株冠层结构来影响枝条寿命。未来需要进一步研究枝条生物量分配、叶片光合能力和呼吸速率在不同生活型物种之间的差异,以便更全面的理解枝条寿命与生境质量之间的关系。     

Quantitative characterization of clumping in Scots pine crowns

Background and Aims

Proper characterization of the clumped structure of forests is needed for calculation of the absorbed radiation and photosynthetic production by a canopy. This study examined the dependency of crown-level clumping on tree size and growth conditions in Scots pine (Pinus sylvestris), and determined the ability of statistical canopy radiation models to quantify the degree of self-shading within crowns as a result of the clumping effect.

Methods

Twelve 3-D Scots pine trees were generated using an application of the LIGNUM model, and the crown-level clumping as quantified by the crown silhouette to total needle area ratio (STAR_crown) was calculated. The results were compared with those produced by the stochastic approach of modelling tree crowns as geometric shapes filled with a random medium.

Key Results

Crown clumping was independent of tree height, needle area and growth conditions. The results supported the capability of the stochastic approach in characterizing clumping in crowns given that the outer shell of the tree crown is well represented.

Conclusions

Variation in the whole-stand clumping index is induced by differences in the spatial pattern of trees as a function of, for example, stand age rather than by changes in the degree of self-shading within individual crowns as they grow bigger.     

纤维桩树脂核用于老年残根残冠修复的效果及对生活质量的影响

目的:探讨老年残根残冠应用纤维桩树脂核修复的临床效果及对病人生活质量的影响。方法:抽选我院行纤维桩树脂核修复的79例(86颗)老年残根残冠患者,对其进行3年随访,观察总体及不同牙位修复成功率和修复前、后生活质量的变化。结果:修复后进行3年随访,86颗残根残冠修复总成功率为95.3%,不同牙位修复成功率无显著差异(P0.05),均在94%以上,86颗牙失败4颗(其中2颗并发牙周炎、2颗牙纤维桩脱落,均未出现牙桩折断);修复后患者生活质量总分及各维度评分均明显优于修复前(P0.05)。结论:纤维桩树脂核是一种极为理想的残冠残根修复材料,能显著提高老年患者术后的生活质量,值得临床推广。