Pollen morphology of the Chloridoideae (Gramineae)

Pollen grains of 57 species (representing 42 genera) of the Chloridoideae have been investigated using light, scanning and transmission electron microscopy. Two aperture patterns and nine exine patterns are distinguished using SEM and TEM. These are categorized into five pollen types. Two pollen types are previously not recorded in Gramineae. A key for the identification of these pollen types is presented. Generally, pollen characters have limited systematic value in recognizing taxa at generic level or above in the Chloridoideae. An evolutionary trend is proposed that awaits verification by further systematic study. Pollen characters can be used as indicators for the areas of origin and distribution of the Chloridoideae.     

虎尾草亚科系统发育关系的初步研究

运用广义形态学性状对虎尾草亚科（Chloridoideae）进行系统发育分析。内类群包括虎尾草亚科52属的69种植物,代表虎尾草亚科的主要类群;芦竹亚科（Arundinoideae）扁芒草族（Danthonieae）的Centropodia和Danthonia被选作外类群。分支分析表明,虎尾草亚科是一个单系类群。其严格一致树包括A、B、C、D、E5个分支。两个大族画眉草族（Eragrostideae）和虎尾草族（Chlorideae）代表虎尾草亚科内部类群分化的两个方向,分开处理较合理。细穗草族（Leptureae）放到虎尾草族中较合理。冠芒草族（Pappophoreae）是虎尾草亚科的基部类群,与画眉草族近缘。我们的研究支持虎尾草亚科从旧世界向新世界扩散的地理分布假说,并提供了虎尾草亚科属上类群的系统发育关系的框架。     

Lemma micromorphological characters in the Chloridoideae (Poaceae) optimized on a molecular phylogeny

Eight lemma micromorphological characters of 83 taxa representing 61 genera in the Chloridoideae have been investigated using Scanning Electron Microscopy, including long cells, cork cells, stomata, bicellular microhairs, papillae, silica cells, microprickles, and macrohairs. Five new types of lemma micromorphological characters were reported here. Data for 27 taxa representing 19 genera from previous publications were also supplied to access the homology of lemma micromorphological characters for different groups through optimization onto a molecular cladogram. Given the optimization, five characters including long cells, cork cells, stomata, papillae, microprickles are of phylogenetic significance for supra-generic groups. Seven characters including straight outline long cells, crescent-shaped cork cells, absent stomata, absent papillae, dumb-bell-shaped silica cells, c-type microprickles, and papillate-base macrohairs may not be homologous, however, the enneapogonoid-type bicellular microhairs appeared as a synapomorphy for the Chloridoideae.     

Inflorescence diversity and evolution in the PCK Clade (Poaceae: Panicoideae: Paniceae)

The PCK Clade, represented by six to nine genera, is a monophyletic group situated within the Paniceae tribe. The highly diverse inflorescences within the PCK Clade provide an interesting system for the study of morphological evolution and also may aid in better understanding its unclear systematics. The inflorescence structure of 110 members of the PCK Clade has been investigated. Inflorescences are polytelic showing different levels of truncation. At least 21 different inflorescence subtypes were identified. Fourteen variable inflorescence characters were found, among which some have suprageneric or infrageneric value and others are polymorphic. A key for the identification of inflorescence types is presented. Nine processes have been identified as responsible for inflorescence diversification. Highly branched inflorescences with different internode lengths are present in the basal genus whereas truncated inflorescence morphologies appear late in the history of the clade. The precise timing of morphological changes is impossible to assess until we have a well supported phylogeny for the PCK Clade.     

Floral displays: genetic control of grass inflorescences

Inflorescences in angiosperms are complex structures that have many different types of meristems. Among complex inflorescences, the best studied are in the grass family. Multiple inflorescence genes have been cloned from grasses over the past few years, many of them by positional cloning using the rice genome as a source of positional information. Several genes affect the apical meristem of the inflorescence differently from the lateral branch meristems, allowing morphological differentiation that permits diversification. ramosa1 (ra1), ra2, and ra3 have been cloned from maize and form part of a network of genes that control the production of lateral branching. Curiously, only ra2 is widely conserved; to date, ra1 and ra3 have been found only in Andropogoneae. Additional domestication genes that affect the inflorescence have also been cloned from maize, rice, and wheat.     

Role of EVERGREEN in the development of the cymose petunia inflorescence

Plants species diverge with regard to the time and place where they make flowers. Flowers can develop from apical meristems, lateral meristems, or both, resulting in three major inflorescence types known as racemes, cymes, and panicles, respectively. The mechanisms that determine a racemose architecture have been uncovered in Arabidopsis and Antirrhinum. To understand how cymes are specified, we studied mutations that alter the petunia inflorescence. Here we show that EVERGREEN (EVG) encodes a WOX homeodomain protein, which is exclusively expressed in incipient lateral inflorescence meristems (IMs), promoting their separation from the apical floral meristem (FM). This is essential for activation of DOUBLE TOP and specification of floral identity. Mutations that change the cymose petunia inflorescence into a solitary flower fully suppress the evg phenotype. Our data suggest a key role for EVG in the diversification of inflorescence architectures and reveal an unanticipated link between the proliferation and identity of meristems.     

Insights into panicoid inflorescence evolution

Inflorescence forms can be described by different combinatorial patterns of meristem fates (indeterminate versus determinate). In theory, the model predicts that any combination is possible. Whether this is true for grasses is unknown. In this paper, the subfamily Panicoideae s.s. (panicoid grasses) was chosen as the model group to investigate this aspect of grass inflorescence evolution. We have studied the inflorescence morphology of 201 species to complement information available in the literature. We have identified the most recurrent inflorescence types and character states among panicoids. Using multivariate approaches, we have indentified correlations among different inflorescence character states. By phylogenetic reconstruction methods we have inferred the patterns of panicoid inflorescence evolution. Our results demonstrate that not all theoretical combinatorial patterns of variation are found in panicoids. The fact that each panicoid lineage has a unique pattern of inflorescence evolution adds an evolutionary component to combinatorial model.     

On the problems of the classification of Chinese bamboos with creeping rhizomes

So far, the 15 genera of bamboos with creeping rhizomes in China have been known. Based on the types and evolution of inflorescence, which have been discussed in the paper, and other criteria of classification, the opinions are given as follows: 1. Some species of Semiarundinaria spp. McClure and Sinobambusa spp. McClure should be separated and regarded as representing a new genus, because the racemes of the some species are different from false inflorescence (indeterminate infl.) of the type species of the two genera, and some other species should be transfered to the genus Pleioblastus. 2. On account of the similarities in the type of inflorescence and pistil, Brachystachyum may be combined with Semiarundinaria. 3. As the inflorescence, pistil and rhizome of Sinarundinaria are similar in those of Fargesia, the two genera should be combined. Due to the inflorescence of Fargesia is different from that of Thamnocalamus, therefore, these two genera must be kept separating. 4. Key to the Genera of Chinese bamboos with creeping rhizomes is provided inthis paper. But the key is available to flowering materials only, because the construction of it is mainly based on reproductive organs.     

Anatomy,trichome morphology and palynology of Salvia chrysophylla Stapf (Lamiaceae)

The anatomy, palynology, morphology and distribution of the trichomes on the aerial parts of Salvia chrysophylla Stapf, an endemic species in Turkey, were studied in order to understand the usefulness of these characteristics for systematic purposes. Some anatomical characters such as (1–)2–24-rowed pith rays in roots, dorsiventral leaves, obviously larger upper epidermal cells, and two to three large vascular bundles in the center and two to four small subsidiary bundles in the wings of petiole provide information of taxonomical significance. Three main types of trichomes were observed on the stem, inflorescence axis, leaf and calyx surfaces of S. chrysophylla. They are peltate, capitate glandular and non-glandular. Capitate glandular and non-glandular trichomes were further subdivided into several kinds. Glandular trichomes are present in abundance on the inflorescence axis and calyx, but non-glandular ones were mainly situated on the leaf and stem. Scanning Electron Microscopy (SEM) studies on the pollen grains have revealed that they are oblate-spheroidal and their exine ornamentation is bireticulate-perforate.     

试论竹类的花序及其演变

本文旨在讨论竹类花序的类型。它共有两大类型,即单次发生花序(简称“真花序”)与续次发生花序(简称“假花序”)。前者具有一延续的花序轴,这与竹类的一般营养轴是迥然不同的;此外,整个花序是在一单次发育的周期内所产生的,并且它在植物体上有着一定的生长部位;它们的基本单位是小穗(真小穗),每小穗通常具一明显的柄。后一类型,则实是竹株的具花枝条,而非是真正的花序,故称为“假花序”。它具有原来就是营养轴所成的“花序轴”,此轴仍有节与节间两部分的区别,仅在其节处始能生有小穗;它们在发生上是续次(successivus)的,其小穗可不固定地着生在植物体任何级别的营养轴之各节,甚至可直接生长在主竿的节上;生长在此种类型花序上的通常或大多是假小穗,它无柄或近于无柄。多数情况都是形成紧密的簇团。又此种类型的花序仅见于竹类的一部分属种中,而决不发现在其他禾草(包括另一部分的竹类)的植株上。作者认为真正的花序可以通过演化而转变为续次发生的花序即“假花序”。举例来说,他曾设想筱竹Thamnocalamus spathiflorus Munro含2-3枚小穗的总状花序能够演化为浦竹仔Indosasa hispida McClure那样形态的一小段花枝。作者还相信在竹类的两大类型的花序之间并非仅有一个方向的演化途径,甚至还可能有着逆向演化之存在。     

Structure of the Cyperaceae Inflorescence

This work presents the basics for interpreting the adult inflorescence structure in Cyperaceae. It provides an analysis of the variations of the synflorescence and inflorescence structure in the family. Three types of synflorescence may be recognized in this family: a synflorescence with a foliate stem, a terminal inflorescence and a variable number of lateral inflorescences; a synflorescence with a foliate stem and only the terminal inflorescence; and a synflorescence with a scape and a terminal inflorescence. Variations in the structure and form of the inflorescences are related to variations in inflorescence branching, inflorescence homogenization degree, presence or absence of the distal part of the inflorescence, phyllotaxis, inflorescence position, types of bracts and leaves subtending branches, elongation of inflorescence internodes and spikelet structure. These variations are correlated with some of the developmental processes that give origin to the inflorescence.     

MORPHOLOGY,EVOLUTION, AND TAXONOMIC SIGNIFICANCE OF THE INFLORESCENCE IN CORDYLANTHUS (SCROPHULARIACEAE)

The genus Cordyhmthus has considerable diversity in its inflorescences while the other genera of tribe Rhinantheae (Scrophulariaceae) uniformly have racemes or spikes. Four distinct inflorescence types are recognized and their homologies and evolutionary history are postulated. Thus it is suggested that the basic florescence type, the elongated spike (Type I), has undergone evolutionary reduction to a few-flowered spike and ultimately to a single-flowered florescence (Type II). Further evolution involving processes of compaction and clustering of the single-flowered florescences has resulted in glomerulate clusters (Type III) and spiciform clusters (Type IV). Knowledge of inflorescence homologies and distribution of the four inflorescence types in the genus has been of considerable aid in formulating a new infrageneric classification. Using evidence primarily from inflorescence, floral, and seed morphology, as well as from geographical distribution and ecology, a classification is proposed establishing three subgenera, namely subg. Dicranostegia, subg. Hemistegia, and subg. Cordylanthus, the last with three sections, sect. Cordylanthus, sect. Anisocheila, and sect. Ramosi.     

Diversity,systematics, and evolution of Cynodonteae inflorescences (Chloridoideae – Poaceae)

The species of the Cynodonteae tribe show great morphological diversity in their reproductive structures. Previous studies where inflorescences were comparatively analysed in the context of phylogeny have shown that although grass inflorescences seem to be excessively variable, there are certain aspects of inflorescences that store relevant information on the evolution and systematics in Poaceae. We have analysed and compared the inflorescence structures of species belonging to the Hilariinae, Monanthochloinae, Scleropogoninae, and Muhlenbergiinae subtribes. Considering the most relevant morphological characters, the most recurrent types of inflorescences in the lineage were determined by means of a principal coordinates analysis. To understand the evolution of inflorescence morphology, ancestral reconstructions of inflorescence characters were performed using the Bayesian inference method. The results obtained demonstrate that the processes of homogenization and truncation might account for the diversity observed in adult inflorescences. Five different types of inflorescences were identified out of 36 theoretical possibilities. Amongst these, inflorescence type 1 (panicle of spikelets, with a terminal spikelet, non-homogenized, and bearing third- or higher-order branches) was found to be the most frequent in the studied group. Ancestral reconstructions of morphological characters allowed us to suggest that the ancestor of the group might have had an inflorescence with the form of a raceme of spikelets, non-truncated and bearing first-order branches. More complex inflorescences bearing no terminal spikelets and having branches of higher order might have diverged this lineage.     

Caryopsis morphology of the Chloridoideae (Gramineae) and its systematic implications

Macro- and micromorphological analysis of the caryopses of 58 taxa belonging to 45 genera of Chloridoideae allows the recognition of three caryopsis types according to differences in ventral face and hilum morphology. First is the convex ventral face, corresponding with a leaf-shaped hilum, observed in the tribe Pappophoreae. Second is the flat ventral face, corresponding with a rudimentary, needle-shaped or oblong hilum, observed in the tribes Eragrostideae and Leptureae. The third type, observed in the tribe Cynodonteae, is the concave ventral face, corresponding with a grooved or triangular hilum. The ventral face and hilum, together with other useful caryopsis characters, including six different shapes, seven types of spermoderm sculpture and three types of stylopodium, may be used as diagnostic characteristics of genera, and even species, in Chloridoideae. A key to identify the different species of 45 genera is provided.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 57–72.     

谷子穗分化的扫描电镜观察

利用扫描电镜对复合品种冀谷１１号的穗分化进行了系统观察,比较了夏谷和春谷穗分化的异同。提出了谷子穗分化划分为穗分化前期、生长锥伸长期、枝梗分化期、小穗和刚毛分化期以及小花分化期共５个时期,就谷子刚毛起源穗分化与栽培育种的关系等问题进行了讨论。     

Morphological traffic between the inflorescence and the vegetative shoot in helobial monocotyledons

Previous studies of reproductive structures in the helobial monocotyledons (Alismatidae) indicate that partitioning between flower and inflorescence is not always clear (e.g.,Lilaea,Scheuchzeria) and that this may be the result of ancestral, unisexual modules coming together to form flowers and/or inflorescences. Later evolutionary changes may have included the inflorescence becoming involved or mixed in with vegetative growth. Substitution of vegetative buds for flowers is the simplest version, and there can be additional modifications to the growth behavior of the inflorescence, such as horizontal growth and dorsiventrality. In the Alismataceae and Limnocharitaceae the derivation of stolonlike structures from inflorescences is obvious: vegetative features have been incorporated into structures that are recognizably inflorescences. In the Hydrocharitaceae the interrelationships between the inflorescence and the vegetative body are much less well defined. We previously suggested forHydrocharis, where a single axillary complex can contain both inflorescence and stolons, that the stolon is basically a sterilized inflorescence and that features of the inflorescence have become incorporated into the vegetative body. Here we will explore this theme further for the Hydrocharitaceae, using information from within and outside the family.     

关于一些植物学术语的中译等问题(三)

(1)确定rhizome的中文译名"根状茎"符合此术语的定义,同时认为另一中文译名"根茎"不符合有关定义,且易引起误解,应予废弃。(2)介绍了在中国植物学文献中稀见的2种属于有限花序类的花序类型,有限伞形花序和有限头状花序。根据有关欧美专家的花序研究,介绍了在中国植物学文献中放在无限花序类的隐头花序和柔荑花序系由聚伞花序演化而出,而应属于有限花序类的论断;同时,作者提出楼梯草属梨序楼梯草组的雄隐头花序系由同属的骤尖楼梯草组的有限头状花序演化而出的论点。     

Macroevolution of panicoid inflorescences: a history of contingency and order of trait acquisition

Background and Aims

Inflorescence forms of panicoid grasses (Panicoideae s.s.) are remarkably diverse and they look very labile to human eyes; however, when performing a close inspection one can identify just a small subset of inflorescence types among a huge morphospace of possibilities. Consequently, some evolutionary constraints have restricted, to some extent, the diversification of their inflorescence. Developmental and genetic mechanisms, the photosynthetic type and plant longevity have been postulated as candidate constraints for angiosperms and panicoids in particular; however, it is not clear how these factors operate and which of these have played a key role during the grass inflorescence evolution. To gain insight into this matter the macroevolutionary aspects of panicoid inflorescences are investigated.

Methods

The inflorescence aspect (lax versus condensed), homogenization, truncation of the terminal spikelet, plant longevity and photosynthetic type were the traits selected for this study. Maximum likelihood and Bayesian Markov chain Monte Carlo methods were used to test different models of evolution and to evaluate the existence of evolutionary correlation among the traits. Both, models and evolutionary correlation were tested and analysed in a phylogenetic context by plotting the characters on a series of trees. For those cases in which the correlation was confirmed, test of contingency and order of trait acquisition were preformed to explore further the patterns of such co-evolution.

Key Results

The data reject the independent model of inflorescence trait evolution and confirmed the existence of evolutionary contingency. The results support the general trend of homogenization being a prerequisite for the loss of the terminal spikelet of the main axis. There was no evidence for temporal order in the gain of homogenization and condensation; consequently, the homogenization and condensation could occur simultaneously. The correlation between inflorescence traits with plant longevity and photosynthetic type is not confirmed.

Conclusions

The findings indicate that the lability of the panicoid inflorescence is apparent, not real. The results indicate that the history of the panicoids inflorescence is a combination of inflorescence trait contingency and order of character acquisition. These indicate that developmental and genetic mechanisms may be important constraints that have limited the diversification of the inflorescence form in panicoid grasses.Key words: Inflorescence, morphology, evolution, panicoids, Panicoideae, Poaceae     

New grass phylogeny resolves deep evolutionary relationships and discovers C4 origins

? Grasses rank among the world's most ecologically and economically important plants. Repeated evolution of the C(4) syndrome has made photosynthesis highly efficient in many grasses, inspiring intensive efforts to engineer the pathway into C(3) crops. However, comparative biology has been of limited use to this endeavor because of uncertainty in the number and phylogenetic placement of C(4) origins. ? We built the most comprehensive and robust molecular phylogeny for grasses to date, expanding sampling efforts of a previous working group from 62 to 531 taxa, emphasizing the C(4)-rich PACMAD (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae and Danthonioideae) clade. Our final matrix comprises c. 5700 bp and is > 93% complete. ? For the first time, we present strong support for relationships among all the major grass lineages. Several new C(4) lineages are identified, and previously inferred origins confirmed. C(3)/C(4) evolutionary transitions have been highly asymmetrical, with 22-24 inferred origins of the C(4) pathway and only one potential reversal. ? Our backbone tree clarifies major outstanding systematic questions and highlights C(3) and C(4) sister taxa for comparative studies. Two lineages have emerged as hotbeds of C(4) evolution. Future work in these lineages will be instrumental in understanding the evolution of this complex trait.