Floral evolution in the Annonaceae: hypotheses of homeotic mutations and functional convergence

The recent publication of hypotheses explaining the homeotic control of floral organ identity together with the availability of increasingly comprehensive and well‐resolved molecular phylogenies presents an ideal opportunity for reassessing current knowledge of floral diversity and evolution in the Annonaceae. This review summarizes currently available information on selected aspects of floral structure and function, including: changes in the number of perianth whorls and the number of perianth parts per whorl; the evolution of sympetaly; the diversity and evolution of pollination chambers (with a novel classification of seven main structural forms of floral chamber based on the different arrangement, size and shape of petals); the evolution of perianth glands; floral unisexuality and hypotheses explaining the unexpectedly high frequency of occurrence of androdioecy; the origin and possible function of inner and outer staminodes; the evolution of stamen connective diversity and theca septation; and the origin of ‘true’ syncarpy and functionally equivalent extragynoecial compita. In each case, current ideas on the origin, evolution and function are discussed. The information presented in this review enables two main conclusions to be drawn. The first is that changes in the homeotic control of floral organ identity may have had a profound impact on floral structure in several disparate lineages in the family. This is most obvious in Fenerivia, in which a centrifugal shift of floral organ identity has occurred, and in Dasymaschalon, in which a reverse (centripetal) shift has occurred. Other genera that have gained or lost entire perianth whorls are likely to have undergone similar homeotic changes. Attention is also drawn to the extensive functional convergence in Annonaceae flowers, with widespread homoplasy in many characters that have previously been emphasized in higher‐level classifications.     

湿室培养获得秦岭地区黏菌种类

通过对陕西省秦岭地区采集的基物进行湿室培养,得到5目5科14属26种黏菌,包括16个陕西省新记录种,初步探讨了黏菌的种类与基物类型关系。     

Water Relations and Leaf Anatomy of the Tropical Species,Jatropha gossypifolia and Alternanthera crucis,Grown Under an Elevated CO2 Concentration

In order to address the question of how elevated CO₂ concentration (EC) will affect the water relations and leaf anatomy of tropical species, plants of Jatropha gossypifolia L. and Alternanthera crucis (Moq.) Bondingh were grown in five EC open top chambers (677 mol mol^–1) and five ambient CO₂ concentration (AC) open top chambers (454 mol mol^–1) with seasonal drought. No effect of EC was found on morning xylem water potential, leaf osmotic potential, and pressure potential of plants of J. gossypifolia. In A. crucis EC caused a significant increase in morning xylem water potential of watered plants, a decrease in osmotic potential, and an increase of 24–79 % in pressure potential of moderately droughted plants. This ameliorated the effects of drought. Stomatal characteristics of both leaf surfaces of J. gossypifolia and A. crucis showed time-dependent, but not [CO₂]-dependent changes. In J. gossypifolia the thickness of whole leaf, palisade parenchyma, and spongy parenchyma, and the proportion of whole leaf thickness contributed by these parenchymata decreased significantly in response to EC. In A. crucis EC caused an increase in thickness of whole leaf, bundle sheath, and mesophyll, while the proportion of leaf cross-section comprised by the parenchymata remained unchanged. These effects disappeared with time under treatment, suggesting that acclimation of the leaf anatomy to the chambers and to EC took place in the successive flushes of leaves produced during the experiment.     

Impact of rising tropospheric ozone on potato: effects on photosynthesis, growth, productivity and yield quality

In view of its importance for human nutrition, the European Commission funded a collaborative research programme (1998–99) to evaluate the impact of future increases in atmospheric ozone (O₃) and carbon dioxide (CO₂) concentrations on yield and tuber quality in potato ( Solanum tuberosum L.). This was the first large-scale open-top chamber project to provide field-based data spanning a wide range of European climatic conditions and ozone concentrations for a widely used cultivar, cv. Bintje. Intensive measurements of physiological and developmental effects were made throughout crop growth to improve the mechanistic understanding of the processes involved. Analysis of the experimental results and modelling work based on the extensive database revealed that the increasing tropospheric O₃ concentrations predicted under future climatic scenarios in Europe are likely to reduce tuber yield in potato. However, season-long exposure to elevated O₃ had both beneficial and detrimental effects on tuber quality. Most of the significant physiological and growth effects occurred during the later stages of crop development, when elevated O₃ reduced photosynthesis and promoted senescence. The observed changes in the quality and nutritional attributes of tubers, such as decreased content of reducing sugars and increased nitrogen concentrations, may be attributable to reduced carbohydrate allocation.     

Echinococcus granulosus:An Intraperitoneal Diffusion Chamber Model of Secondary Infection in Mice

Breijo, M., Spinelli, P., Sim, R.B., and Ferreira, A. M. 1998.Echinococcus granulosus:An intraperitoneal diffusion chamber model of secondary infection in mice.Experimental Parasitology90, 270–276. The present work describes a new experimental model of secondary infection which allows, through the recovery of the parasite together with its localin vivoenvironment, examination of the local nonadaptive immune response of the infected host and the differentiation of the parasite from protoscoleces to cysts. In this model we administered protoscoleces within silicone diffusion chambers, previously implanted into the peritoneal cavities of mice. The process of designing the model involved, first, determination of the optimal time postimplantation to infect the mice and, second, evaluation of the parasite's ability to establish infection within the chambers. The optimal time for infection was considered to be after the inflammation caused by implantation of the chambers had subsided. Our results showed that by day 20 postsurgery, three parameters used as indications of inflammation (complement C3, serum amyloid P protein, and polymorphonuclear cells in the peritoneum and in the chamber contents) had reverted to their normal levels. In our study of parasite differentiation, we found that 2–3% of the total number of parasites inoculated into the chambers were recovered as viable cysts after 100 days. Throughout the infection period, the population of parasites recovered was heterogeneous; certain parasite morphologies that have not been described previously were observed. In conclusion, the use of intraperitoneal diffusion chambers offers a potential tool for investigating thein vivodifferentiation process of secondary cysts ofEchinococcus granulosusin mice and the early local interactions between host and parasite during this process.     

Xylem water transport: is the available evidence consistent with the cohesion theory?

Since its introduction in the late 19th century, the so-called cohesion theory has become widely accepted as explaining the mechanism of the ascent of sap. According to the cohesion theory, the minimum standing vertical xylem tension gradient should be 0·01 MPa m⁻¹. When transpiration is occurring, frictional resistances are expected to make this gradient considerably steeper. The results of numerous pressure chamber measurements reported in the literature are generally regarded as corroborating the cohesion theory. Nevertheless, several reports of pressure chamber measurements in tall trees appear to be incompatible with predictions of the cohesion theory. Furthermore, the pressure chamber is an indirect method for inferring xylem pressure, which, until recently, has not been validated by comparison against a direct method. The xylem pressure probe provides a means of testing the validity of the pressure chamber and other indirect techniques for estimating xylem pressure. We discuss here the results of concurrent measurements made with the pressure chamber and the xylem pressure probe, particularly recent measurements made at the top of a tall tropical tree during the rainy season. These measurements indicate that the pressure chamber often substantially overestimates the tension previously existing in the xylem, especially in the partially dehydrated tissue of droughted plants. We also discuss other evidence obtained from classical and recent approaches for studying water transport. We conclude that the available evidence derived from a wide range of independent approaches warrants a critical reappraisal of tension-driven water transport as the exclusive mechanism of long-distance water transport in plants.     

双阳极室甲烷微生物燃料电池同步脱氮除硫性能及微生物群落分析

【背景】甲烷厌氧氧化(anaerobic oxidation of methane, AOM)包含反硝化型甲烷厌氧氧化和硫酸盐还原型甲烷厌氧氧化。目前,人们向水体中排放过量的含氮及含硫污染物,引起了严重的环境污染和生态破坏。【目的】利用甲烷厌氧氧化微生物燃料电池(microbial fuel cell, MFC)研究同步脱氮除硫耦合反应机理及反应过程中微生物的多样性信息。【方法】构建了3个微生物燃料电池(N-S-MFC、N-MFC、S-MFC),以甲烷作为唯一碳源,探究其同步脱氮除硫性能,并采用16S rRNA基因高通量测序技术对微生物群落结构进行分析。【结果】N-S-MFC中硝酸盐和硫酸盐的去除率分别为90.91%和18.46%。阳极室中微生物的相对丰度提高,与反硝化及硫酸盐还原菌相关的微生物大量富集,如门水平上拟杆菌门(Bacteroidota)、厚壁菌门(Firmicutes)和脱硫杆菌门(Desulfobacterota),同时属水平上Methylobacterium＿Methylorubrum、Methylocaldum、Methylomonas等常见的甲烷氧化菌增多。【结论...     

Temporal variation in nitrous oxide (N2O) fluxes from an oil palm plantation in Indonesia: An ecosystem-scale analysis

The rapidly growing areal extent of oil palm (Elaeis guineensis Jacq.) plantations and their high fertilizer input raises concerns about their role as substantial N₂O sources. In this study, we present the first eddy covariance (EC) measurements of ecosystem-scale N₂O fluxes in an oil palm plantation and combine them with vented soil chamber measurements of point-scale soil N₂O fluxes. Based on EC measurements during the period August 2017 to April 2019, the studied oil palm plantation in the tropical lowlands of Jambi Province (Sumatra, Indonesia) is a high source of N₂O, with average emission of 0.32 ± 0.003 g N₂O-N m⁻² year⁻¹ (149.85 ± 1.40 g CO₂-equivalent m⁻² year⁻¹). Compared to the EC-based N₂O flux, average chamber-based soil N₂O fluxes (0.16 ± 0.047 g N₂O-N m⁻² year⁻¹, 74.93 ± 23.41 g CO₂-equivalent m⁻² year⁻¹) are significantly (~49%, p < 0.05) lower, suggesting that important N₂O pathways are not covered by the chamber measurements. Conventional chamber-based N₂O emission estimates from oil palm up-scaled to ecosystem level might therefore be substantially underestimated. We show that the dynamic gas exchange of the oil palm canopy with the atmosphere and the oil palms' response to meteorological and soil conditions may play an important but yet widely unexplored role in the N₂O budget of oil palm plantations. Diel pattern of N₂O fluxes showed strong causal relationships with photosynthesis-related variables, i.e. latent heat flux, incoming photosynthetically active radiation and gross primary productivity during day time, and ecosystem respiration and soil temperature during night time. At longer time scales (>2 days), soil temperature and water-filled pore space gained importance on N₂O flux variation. These results suggest a plant-mediated N₂O transport, providing important input for modelling approaches and strategies to mitigate the negative impact of N₂O emissions from oil palm cultivation through appropriate site selection and management.     

Formation of the inner branchiostegal cuticle of the blue crab,Callinectes sapidus

The noncalcified inner branchiostegal cuticle, which lines the branchial chamber, was examined histologically and ultrastructurally over the molt cycle in the blue crab, Callinectes sapidus. In intermolt crabs (stage C₄) the epithelium underlying the inner cuticle is cuboidal and has abundant intercellular spaces and a prominent basement membrane. Apolysis occurs at stage D₀ and dissolution of the cuticle is accompanied by the formation of numerous lysosomes in the epithelium. During stage D₁, cells increase in height, apical mitochondria become more abundant, and the cuticle continues to be resorbed. An epicuticle is formed in early D₂, arising from a fusion of small subunits apparently attached to short apical microvilli. Cuticle deposition continues through D₂ and is complete by stage D₃. By the time cuticle deposition is complete, the epithelium has become extremely columnar and cells are filled with bundles of microtubules. In stage D₄, an amorphous electron‐dense core appears in the microtubule‐filled cells, which are attached to the cuticle at their apical end and anchored to their basement membrane at the basal surface. These microtubule‐filled cells persist through ecdysis, stage E, but during stage A₁ the cores disappear and some organelles begin to reappear in the cytoplasm. By stage A₂, the cells return to the cuboidal morphology seen in intermolt and remain so throughout the remainder of the molt cycle. This new pattern of cuticle deposition resembles that observed in the gills of crustaceans in that the cuticle is uncalcified and there is no postecdysial cuticle formation. However, instead of apolysis being delayed until just before ecdysis, the inner cuticle is formed during the first half of premolt, allowing the epithelial cells time to differentiate into a morphology that provides tensile strength for the stress of ecdysis. These new observations demonstrate that cuticle formation can follow very diverse structural and temporal patterns. In order to integrate and coordinate these diverse patterns, it is suggested that a suite of feedback mechanisms must be present. J. Morphol. 240:267–281, 1999. © 1999 Wiley‐Liss, Inc.