Photosynthesis of Resurrection Angiosperms

Resurrection plants which are able to quickly reactivate after falling into a period of anabiosis caused by dehydration have been very rare among angiosperms, especially among dicotyledons whose chlorophyll content and chloroplast structure little changed in the course of desiccation, therefore has been called homoiochlorophyllous desiccation-tolerant plants (HDTs). Another type of resurrection angiosperms that lost its chlorophyll dining desiccation is called poikilochlorophyllous desiccation-tolerant plants (PDTs). HDTs have been received more attention because of simplicity of protection mechanism which is much easy to the study and utilization of the desiccation tolerance of resurrection angiosperms. Recent advances in studies of photosynthesis of resurrection angiosperms indicate that photochemical activities are sensitive indicators for the study of physiological state of resurrection angiosperms during desiccation and rehydration. Photochemical activities of resurrection angiosperms are inhibited with loss of water similar to those of general plants, however, the magic thing is that they could reactivate rapidly during rehydration even losing more than 95% water. Up-regulations in xanthophyll cycle and antioxidative systems as well as preservation in integrity and stability of photosynthetic membranes during desiccation may be very important to desiccation tolerance of resurrection angiosperms. The fact that phosphate treatment in rehydration stage also strongly influences resurrection indicated importance of studies on rehydration stages of resurrection angiosperms.

In Vitro Fertilization of Angiosperms-10-Year Effort in China

This review gives a brief retrospect to the development on in vitro fertilization (IVF) of angiosperms in China. During the last decade Chinese scientists put great enthusiasm and efforts on IVF system construction and built up notable contributions to the flourish of this field. Keeping pace with international development and participating international cooperation in the field of IVF, Chinese scientists have now focused on the investigation of basic mechanism relevant to possible gamete interaction, egg cell activation and early embryogenesis by IVF. In vitro manipulation techniques are combined with cytological and molecular biological approaches to unveil the double fertilization mysteries.

A Biased, Misleading Review on Early Angiosperms

A recently published review by Herendeen?et al.?is misleading, self-centered, self-praising, and self-conflicting. They excluded the famous early angiosperm?Archaefructus?from their list of exemplar angiosperms, which contained only fossil plants they published themselves, leaving the impression that they were only authoritative on the origin and early history of angiosperms. Their 57-year-old “No Angiosperms Until the Cretaceous” conception does not reflect the truth about the origin and early history of angiosperms. Reinforcing such vapidly repeated statement does not help resolving any problem in science but leads to no solution for the origin of angiosperms. The authors tried to establish a criterion identifying a fossil angiosperm but their own exemplar angiosperm?Monetianthus?overturns their own criterion. Apparently, such a review does not positively contribute much to science.

Origin of Angiosperms and Their Diversification in the Cretaceous

The dominating hypothesis stated that angiosperms originated in the Early Cretaceous, there were no pre-Cretaceous angiosperms, and carpels (the basic units of gynoecium) were derived from former megasporophylls bearing ovules/seeds along their margins through longitudinally folding and enrolling. However, there are increasing evidences of pre-Cretaceous angiosperms, the assumed megasporophyll actually does not exist, and the Cretaceous-only history of angiosperms appears much shorter than suggested by molecular clocks. Here I will integrate new knowledge of living and fossil plants to give a plausible explanation for the origin and early evolution of angiosperms. Several lines of evidence indicate that the ancestor of angiosperms may well have been present in the Triassic. The former gap between angiosperms and gymnosperms is artificial. Some Triassic fossils playing a role intermediate between angiosperms and gymnosperms seem to favor the Unifying Theory.

Late Cretaceous Aquatic Angiosperms from Jiayin,Heilongjiang,Northeast China

Three taxa of Late Cretaceous aquatic angiosperms, Queruexia angulata （Lesq.） Krysht., Cobbania corrugata （Lesq.） Stockey et al. and Nelumbites cf. extenuinervis Upchurch et al. from Jiayin of Heilongjiang, NE China, are described in detail. Among them, Cobbania and Nelumbites from the Upper Cretaceous in China are reported for the first time. The aquatic angiosperm assemblage of Queruexia-Cobbania-Nelumbites appears to imply a seasonal, warm and moist environment in the Jiayin area during the Santonian-Campanian time.

Mid-Cretaceous Hothouse Climate and the Expansion of Early Angiosperms

The remarkable transition of early angiosperms from a small to a dominant group characterized the terrestrial ecosystem of the Cretaceous. This transition was instigated and promoted by environmental changes. Mid-Cretaceous is characterized by major geological events that affected the global environment. δ^18O, palaeothermometer TEX86, and other climatic indices from marine sediments suggest rapid temperature increase during mid-Cretaceous despite occasional short cooling events. Simultaneously, terrestrial deposits in East Asia changed from coal-bearing to shale, then to red beds and evaporites. Plant assemblages and other paleoclimate indicators point to rapid aridification for midCretaceous terrestrial environments. In addition, the wildfires were frequently spread all over the earth by the numerous charcoal evidence during the Mid-Cretaceous. Thus, we speculate that the seasonally dry and hot conditions of mid-Cretaceous created a fiery hothouse world. Early angiosperms increased in abundance and diversity and evolved from a few aquatic species to terrestrial herbaceous and then to the diversified flora of today. Angiosperms showed rapid physiological evolution in vein density and leaf area that improved photosynthesis and water absorption. These ecophysiological changes made early angiosperms well adapted to the hot and dry environment in mid-Cretaceous. Moreover, these physiological changes facilitated the fire–angiosperm cycles in mid-Cretaceous that likely further stimulated the early angiosperm evolution.

Comparative Studies of Tracheary Element Structure of Some Gymnosperms with Angiosperms

Tissues of the pinna and rachis of Cycas diannaensis and pinna, rachis, and root of Cycas taiwaniana, rachis of Cycas szechuanensis, stem of Metasequoia glyptostroboides (Taxodiaceae), stems of Chamaecyparis obtusa (Sieb.et Zucc.) Endl cv. Tetragona (Cupressaceae), and leaves and stems of Michelia alba and Michelia figo and stems of Amygdalus persica (angiosperms) were compared using the scanning electron microscopy. In all species of these gymnosperms, their many tracheary elemnts have perforations in end walls and lateral walls. These structures are the same as vessels of angiosperms;therefore, these tracheary elements are vessel elements. Many types of vessels were found in cycads: pitted vessels in M. glyptostroboides, spiral and pitted vessels in Chamaecyparis obtusa cv. Tetragona. The development and structural characteristics of vessels of cycads, the two other gymnosperms, and the angiosperms were identical. Some characters such as extent of incline of perforation plate in the end wall showed that vessel characters of some angiosperms were more primitive than the cycads or M. glyptostroboides and C. obtusa cv. Tetragona. Many of the vessel elements of the angiosperms were band shaped, without end walls, and had only two lateral walls and other two margins;the end was acuate or with an arc margin;the end of some vessel elements was acute with no perforations, many perforations located only in lateral wall. Such results are rarely reported in previous work. In all species, perforations were seen only in tracheae, and the walls of parenchyma cells only had a thin primary wall and without perforation. Analysis and discussion to the experimental measures which were observed and research of the structure of vessel or tracheid, pointed out that several measures all could be used and the Jeffrey’ method effects were better. Comparing the vessels of cycads, Taxodiaceae and Cupressaceae helps us to understand the mechanism in which these most primitive or more primitive extant gymnosperms were adapted to harsh environments and to understand these species’ evolutionary extent, and has the significance to the studies of plant anatomy, plant systematics and plant evolution.

Androecium of Archaefructus, the Late Jurassic Angiosperms from Western Liaoning, China

Androecium of the earliest known flowering plant Archaefructus liaoningensis was found from the Upper Jurassic Jianshangou Formation of western Liaoning, China. The androecium consists of numerous stamens bearing in pair on the reproductive axes below conduplicate carpels. The stamens are composed of a short filament and basifixed anther for each. Monosulcate pollen in situ are found from the anthers. The characters of the androecium reveals that Archaefructus are probably protandrous, and the paired stamens and monosulcate pollen appear to indicate that Archaefructus, as primitive angiosperms,might be derived from extinct seed -ferns during the Older Mesozoic. Archaefructus is considered Late Jurassic in age.

Nuclear phylogenomics of angiosperms and insights into their relationships and evolution

Angiosperms(flowering plants) are by far the most diverse land plant group with over 300,000 species. The sudden appearance of diverse angiosperms in the fossil record was referred to by Darwin as the “abominable mystery,”hence contributing to the heightened interest in angiosperm evolution. Angiosperms display wide ranges of morphological, physiological,and ecological characters, some of which have probably influenced their species richness. The evolutionary analyses of these characteristics help to address questions of angiosperm diversification and require well resolved phylogeny. Following the great successes of phylogenetic analyses using plastid sequences,dozens to thousands of nuclear genes from next-generation sequencing have been used in angiosperm phylogenomic analyses, providing well resolved phylogenies and new insights into the evolution of angiosperms. In this review we focus on recent nuclear phylogenomic analyses of large angiosperm clades, orders, families,and subdivisions of some families and provide a summarized Nuclear Phylogenetic Tree of Angiosperm Families. The newly established nuclear phylogenetic relationships are highlighted and compared with previous phylogenetic results. The sequenced genomes of Amborella,Nymphaea, Chloranthus, Ceratophyllum, and species of monocots, Magnoliids, and basal eudicots, have facilitated the phylogenomics of relationships among five major angiosperms clades. All but one of the 64 angiosperm orders were included in nuclear phylogenomics with well resolved relationships except the placements of several orders. Most families have been included with robust and highly supported placements, especially for relationships within several large and important orders and families.Additionally, we examine the divergence time estimation and biogeographic analyses of angiosperm on the basis of the nuclear phylogenomic frameworks and discuss the differences compared with previous analyses. Furthermore,we discuss the implications of nuclear phylogenomic analyses on ancestral reconstruction of morphological, physiological, and ecological characters of angiosperm groups, limitations of current nuclear phylogenomic studies, and the taxa that require future attention.

Global multifaceted biodiversity patterns,centers,and conservation needs in angiosperms

The Convention on Biological Diversity seeks to conserve at least 30%of global land and water areas by 2030,which is a challenge but also an opportunity to better preserve biodiversity,including flowering plants(angiosperms).Herein,we compiled a large database on distributions of over 300,000 angiosperm species and the key functional traits of 67,024 species.Using this database,we constructed biodiversity-environment models to predict global patterns of taxonomic,phylogenetic,and functional diversity in terrestrial angiosperms and provide a comprehensive mapping of the three diversity facets.We further evaluated the current protection status of the biodiversity centers of these diversity facets.Our results showed that geographical patterns of the three facets of plant diversity exhibited substantial spatial mismatches and nonoverlapping conservation priorities.Idiosyncratic centers of functional diversity,particularly of herbaceous species,were primarily distributed in temperate regions and under weaker protection compared with other biodiversity centers of taxonomic and phylogenetic facets.Our global assessment of multifaceted biodiversity patterns and centers highlights the insufficiency and unbalanced conservation among the three diversity facets and the two growth forms(woody vs.herbaceous),thus providing directions for guiding the future conservation of global plant diversity.

A novel protein domain is important for photosystem Ⅱ complex assembly and photoautotrophic growth in angiosperms

Photosystem Ⅱ(PSⅡ)is a multi-subunit protein complex of the photosynthetic electron transport chain that is vital to photosynthesis.Although the structure,composition,and function of PSⅡ have been extensively studied,its biogenesis mechanism remains less understood.Thylakoid rhodanese-like(TROL)provides an anchor for leaf-type ferredoxin:NADP^(+)oxidoreductase.Here,we report the chacterizaton of a second type of TROL protein,TROL2,encoded by seed plant genomes whose function has not previously been reported.We show that TROL2 is a PSⅡ assembly cofactor with essential roles in the establishment of photoautotrophy.TROL2 contains a 45-amino-acid domain,termed the chlorotic lethal seedling(CLS)domain,that is both necessary and sufficient for TROL2 function in PSⅡ assembly and photoautotrophic growth.Phylogenetic analyses suggest that TROL2 may have arisen from ancestral TROL1 via gene duplication before the emergence of seed plants and acquired the CLS domain via evolution of the sequence encoding its N-terminal portion.We further reveal that TROL2(or CLS)forms an assembly cofactor complex with the intrinsic thylakoid membrane protein LOW PSⅡ ACCUMULATION2 and interacts with small PSⅡ subunits to facilitate PSⅡ complex assembly.Collectively,our study not only shows that TROL2(CLS)is essential for photoautotrophy in angiosperms but also reveals its mechanistic role in PSⅡ complex assembly,shedding light on the molecular and evolutionary mechanisms of photosynthetic complex assemblyin angiosperms.

Evolutionary history shapes variation of wood density of tree species across the world

The effect of evolutionary history on wood density variation may play an important role in shaping variation in wood density,but this has largely not been tested.Using a comprehensive global dataset including 27,297 measurements of wood density from 2621 tree species worldwide,we test the hypothesis that the legacy of evolutionary history plays an important role in driving the variation of wood density among tree species.We assessed phylogenetic signal in different taxonomic(e.g.,angiosperms and gymnosperms)and ecological(e.g.,tropical,temperate,and boreal)groups of tree species,explored the biogeographical and phylogenetic patterns of wood density,and quantified the relative importance of current environmental factors(e.g.,climatic and soil variables)and evolutionary history(i.e.,phylogenetic relatedness among species and lineages)in driving global wood density variation.We found that wood density displayed a significant phylogenetic signal.Wood density differed among different biomes and climatic zones,with higher mean values of wood density in relatively drier regions(highest in subtropical desert).Our study revealed that at a global scale,for angiosperms and gymnosperms combined,phylogeny and species(representing the variance explained by taxonomy and not direct explained by long-term evolution process)explained 84.3%and 7.7%of total wood density variation,respectively,whereas current environment explained 2.7%of total wood density variation when phylogeny and species were taken into account.When angiosperms and gymnosperms were considered separately,the three proportions of explained variation are,respectively,84.2%,7.5%and 6.7%for angiosperms,and 45.7%,21.3%and 18.6%for gymnosperms.Our study shows that evolutionary history outpaced current environmental factors in shaping global variation in wood density.

Complete chloroplast genome sequences of Schisandra chinensis:genome structure,comparative analysis,and phylogenetic relationship of basal angiosperms

Dear Editor, Schisandra chinensis （Turcz.） Baill. belongs to family Schisandraceae. Its fruit called ＂Wu Wei Zi＂ in Chinese is a well-known medicinal material, which is used to treat chronic cough and dyspnea, nocturnal emission, enuresis, etc. （National Pharmacopoeia Committee, 2015）. Except for S. chinensis, many species of Schisandraceae, such as S. sphenanthera, S. lancifolia and S. rubriflora, are used as the original olants of folk medicines.

Global patterns and ecological drivers of taxonomic and phylogenetic endemism in angiosperm genera

Endemism of lineages lies at the core of understanding variation in community composition among geographic regions because it reflects how speciation,extinction,and dispersal have influenced current distributions.Here,we investigated geographic patterns and ecological drivers of taxonomic and phylogenetic endemism of angiosperm genera across the world.We identify centers of paleo-endemism and neo-endemism of angiosperm genera,and show that they are mostly located in the Southern Hemisphere in tropical and subtropical regions,particularly in Asia and Australia.Different categories of phylogenetic endemism centers can be differentiated using current climate conditions.Current climate,historical climate change,and geographic variables together explained~80%of global variation in taxonomic and phylogenetic endemism,while 42-46%,1%,and 15%were independently explained by these three types of variables,respectively.Thus our findings show that past climate change,current climate,and geography act together in shaping endemism,which are consistent with the findings of previous studies that higher temperature and topographic heterogeneity promote endemism.Our study showed that many centers of phylogenetic endemism of angiosperms,including regions in Amazonia,Venezuela,and west-central tropical Africa that have not previously been identified as biodiversity hotspots,are missed by taxon-based measures of endemism,indicating the importance of including evolutionary history in biodiversity assessment.

Widespread Whole Genome Duplications Contribute to Genome Complexity and Species Diversity in Angiosperms

Gene duplications provide evolutionary potentials for generating novel functions, while polyploidization or whole genome duplication （WGD） doubles the chromosomes initially and results in hundreds to thousands of retained duplicates. WGDs are strongly supported by evidence commonly found in many species-rich lineages of eukaryotes, and thus are considered as a major driving force in species diversification. We per- formed comparative genomic and phylogenomic analyses of 59 public genomes/transcriptomes and 46 newly sequenced transcriptomes covering major lineages of angiosperms to detect large-scale gene dupli- cation events by surveying tens of thousands of gene family trees. These analyses confirmed most of the previously reported WGDs and provided strong evidence for novel ones in many lineages. The detected WGDs supported a model of exponential gene loss during evolution with an estimated half-life of approx- imately 21.6 million years, and were correlated with both the emergence of lineages with high degrees of diversification and periods of global climate changes. The new datasets and analyses detected many novel WGDs widely spread during angiosperm evolution, uncovered preferential retention of gene functions in essential cellular metabolisms, and provided clues for the roles of WGD in promoting angiosperm radiation and enhancing their adaptation to environmental changes.

Variations in leaf characteristics of three species of angiosperms with changing of altitude in Qilian Mountains and their inland high-altitude pattern

In this study, 39 leaf samples of three angiosperms （Betula albo-sinensis, tree species; and Caragana jubata and Berberis diaphana, shrub species） were collected in the middle-east parts at 2300-3640 m asl of the Qilian Mountains to study the varia- tions of leaf characteristics of angiosperms with altitude change in inland high-altitude regions of China. Five leaf indexes, viz. epidermal cell density （ED）, stomatal density （SD）, stomatal index （SI）, leaf vein density （VD） and carbon isotopic ratio （c^13C） were analyzed in laboratory. The results show that there are significant or even very significant linear correlations between the five indexes and altitude, of which SD, SI and VD exhibit a negative correlation with altitude, while ED and Ot3C exhibit a positive correlation with altitude. Such a correlation assemblage is quite different from the situation in the low-altitude humid environment. Generally, only an assemblage of positive correlations can be observed between the indexes （viz. SD, SI and （~3C, etc.） and the altitude in the low-altitude humid environment, which were caused mainly by the plants＇ responses to the change of atmospheric CO2 concentration （Co）. However, an assemblage of the negative and positive correlations found here may be attributed mainly to the plants＇ responses to the change of physiological drought caused by change of low temperature, and here it is preliminarily called the inland high-altitude pattern of plant leaf variations.

Climatic correlates of phylogenetic relatedness of woody angiosperms in forest communities along a tropical elevational gradient in South America

Aims This study assesses the relationship between phylogenetic relat-edness of angiosperm tree species and climatic variables in local forests distributed along a tropical elevational gradient in South America.In particular,this paper addresses two questions:Is phylo-genetic relatedness of plant species in communities related to tem-perature variables more strongly than to water variables for tropical elevational gradients?Is phylogenetic relatedness of plant species in communities driven by extreme climatic conditions(e.g.minimum temperature(MT)and water deficit)more strongly than by climatic seasonal variability(e.g.temperature seasonality and precipitation seasonality)?Methods I used a set of 34 angiosperm woody plant assemblages along an elevational gradient in the Andes within less than 5 degrees of the equator.Phylogenetic relatedness was quantified as net relatedness index(NRI)and nearest taxon index(NTI)and was related to major climatic variables.Correlation analysis and structure equation modeling approach were used to assess the relationships between phylogenetic relatedness and climatic variables.Important Findings Phylogenetic relatedness of angiosperm woody species in the local forest communities is more strongly associated with temperature-related variables than with water-related variables,is positively cor-related with mean annual temperature(MAT)and MT,and is related with extreme cold temperature more strongly than with seasonal temperature variability.NTI was related with elevation,MAT and MT more strongly than was NRI.Niche convergence,rather than niche conservatism,has played a primary role in driving community assem-bly in local forests along the tropical elevational gradient examined.Negative correlations of phylogenetic relatedness with elevation and higher correlations of phylogenetic relatedness with elevation and temperature for NTI than for NRI indicate that evolution of cold toler-ance at high elevations in tropical regions primarily occurred at recent(terminal)phylogenetic nodes widely distributed among major clades.

An Early Fossil Flower of Angiosperms From Northeast China

In the last two decades, paleobotanists paid attention to seeking and studying fossils of angiosperm flowers. In particular, the Cretaceous and Tertiary flowers discovered from Sweden and North America are well-preserved, some as three-dimensional charcoal fossils. Such valuable specimens provided more important details of floral structure, insect-and wind-pollination mechanisms of early angiosperms. Based on the

Intercontinental comparison of phylogenetic relatedness in introduced plants at the transition from naturalization to invasion:A case study on the floras of South Africa and China

Invasive species may pose significant threats to biodiversity and ecosystem structure and functioning.The number of introduced species that have become invasive is substantial and is rapidly increasing.Identifying potentially invasive species and preventing their expansion are of critical importance in invasion ecology.Phylogenetic relatedness between invasive and native species has been used in predicting invasion success.Previous studies on the phylogenetic relatedness of plants at the transition from naturalization to invasion have shown mixed results,which may be because different methods were used in different studies.Here,I use the same method to analyze two comprehensive data sets from South Africa and China,using two phylogenetic metrics reflecting deep and shallow evolutionary histories,to address the question whether the probability of becoming invasive is higher for naturalized species distantly related to the native flora.My study suggests that the probability of becoming invasive is higher for naturalized species closely related to the native flora.The finding of my study is consistent with Darwin's preadaptation hypothesis.

Global patterns of taxonomic and phylogenetic diversity of flowering plants: Biodiversity hotspots and coldspots

Species diversity of angiosperms(flowering plants) varies greatly among regions.Geographic patterns of variation in species diversity are shaped by the interplay of ecological and evolutionary processes.Here,using a comprehensive data set for regional angiosperm floras across the world,we show geographic patterns of taxonomic(species) diversity,phylogenetic diversity,phylogenetic dispersion,and phylogenetic deviation(i.e.,phylogenetic diversity after accounting for taxonomic diversity) across the world.Phylogenetic diversity is strongly and positively correlated with taxonomic diversity;as a result,geographic patterns of taxonomic and phylogenetic diversity across the world are highly similar.Areas with high taxonomic and phylogenetic diversity are located in tropical regions whereas areas with low taxonomic and phylogenetic diversity are located in temperate regions,particularly in Eurasia and North America,and in northern Africa.Similarly,phylogenetic dispersion is,in general,higher in tropical regions and lower in temperate regions.However,the geographic pattern of phylogenetic deviation differs substantially from those of taxonomic and phylogenetic diversity and phylogenetic dispersion.As a result,hotspots and coldspots of angiosperm diversity identified based on taxonomic and phylogenetic diversity and phylogenetic dispersion are incongruent with those identified based on phylogenetic deviations.Each of these metrics may be considered when selecting areas to be protected for their biodiversity.