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.     

<Emphasis Type="Italic">Miconia rondoniensis</Emphasis> (Melastomataceae), a new species from the Southern Amazon of Brazil

Miconia rondoniensis occurs in secondary upland (terra firme) moist open forest in the Brazilian states of Rondônia, Mato Grosso and Amazonas. It can be recognized by the tree habit, large leaves with rounded to obtuse or subcordate bases and 5+2 basal veins (five main veins plus a faint submarginal pair), large inflorescences with proximal paraclades bearing quaternary branches and distal paraclades bearing tertiary branches, persistent hemi-elliptic bracteoles, short persistent calyx lobes, and capitate stigmas. The most striking feature of this new species is the thick pubescence on the branches and petioles, composed of trichomes having a long axis and short arms at the base, but inflated and lacking arms at the apex, resulting in a sorus-like surface covered with globose structures.     

Multiple origins of congested inflorescences in Cyperus s.s. (Cyperaceae): Developmental and structural evidence

? Premise of the study: The understanding of homoplasic structures becomes more relevant when they are complex and define large angiosperm taxa. Inflorescence architecture usually fulfills both features, as happens with Cyperus, a genus with two taxonomical subdivisions characterized either by alternative expressions of Kranz anatomy (C(3) or C(4)) or inflorescence shape (condensed or lax). Those subdivisions are not completely congruent because at least one of these presumed characters has evolved several times. We focused a SEM study on the inflorescence development in species with condensed inflorescences and different photosynthetic anatomy to test the possibility that condensed inflorescences of subgen. Anosporum (C(3) anatomy) have evolved independently from those of subgen. Cyperus (C(4) anatomy). ? Methods: Freshly collected inflorescences of C. entrerianus, C. eragrostis, C. oxylepis, and C. incomtus were studied using stereoscopic and scanning electron microscopy. ? Key results: Condensed inflorescences of Cyperus species with C(3) and C(4) anatomy had differences in structure and development: (1) mature structure, (2) position of second-order branching initiation in the first developmental stage of the inflorescence, (3) main axis development and elongation, and branching development, (4) types of ramifications, (5) phyllotaxis and symmetry. ? Conclusions: Results support multiple origins of condensed inflorescences in Cyperus, based especially on differences in timing during development and elongation of the main axis and branches, branching pattern and phyllotaxis. Structure and development may be the key to using inflorescence morphology as an external feature to distinguish large natural groups within Cyperus based on vegetative anatomy.     

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.     

宽叶兔儿风花序侧生分枝的变异式样以及分枝兔儿风的分类地位问题

宽叶兔儿风Ainsliaealatifolia花序主轴上的侧生分枝通常被描述为由单个或2–4个头状花序聚集而组成的簇生花序。作者在野外和标本馆中仔细研究了该种居群内侧生分枝花序形态的变异,依据其简化和集中的程度在居群内区分出3种花序类型:简单的复合聚伞花序、复杂的复合聚伞花序以及两者之间的过渡类型,具有后面两种类型的个体在居群内少见。这一发现不仅为探讨兔儿风属内各种花序的演化提供了新的线索,而且为理清宽叶兔儿风这一地理广布种的分类学问题提供了新的视野。居群内有些侧生分枝为复杂的复合聚伞花序类型的个体整个花序的主轴折断了,这是由于整个主轴顶端部分被昆虫蛀食或者其他外力造成的。值得注意的是分枝兔儿风Ainsliaealatifoliavar.ramifera的主模式就属于这种情况。分枝兔儿风和宽叶兔儿风原变种之间在分布区、生境以及物候上并没有明显的分化,因此分枝兔儿风被处理成宽叶兔儿风的异名。     

Probleme der Infloreszenztypologie vonW. Troll

In contrast toW. Troll's typology of inflorescences which aims at more or less rigid, well defined types, this investigation accentuates the processes that constitute the evolutionary transformations leading from one typical form to another.Troll divided the inflorescences into the two types of monotelic and polytelic synflorescences, the first with a terminal flower on the main axis, the latter with a homogeneous florescence on the indeterminate axis. Both forms are enriched by proximal branches which repeat the structure of the main axis (paracladia). The evolutionary processes leading from the more primitive monotelic type to the advanced polytelic type are truncation (loss of the terminal flower) and homogenization of the distal branches, which thus form a homogeneous florescence. A closer survey of the polytelic groups reveals the fact that, usingTroll's criteria, the same distinction can be found within these groups themselves. Loss of the terminal florescence (truncation of 2nd and higher degree) as well as homogenization of the distal paracladia may lead to florescence-like units of higher complexity. Examples can be found inAsteraceae (Figs. 1 and 2),Fabaceae (Fig. 3 a),Mimosaceae (Fig. 3 b),Acanthaceae, and also in Monocots, as exemplified by theMarantaceae (Figs. 4 and 5). The so-called racemization (inversion of efflorescences from basipetalous to acropetalous) may be mentioned as a third element of transformation, emphasizing the unity of the florescences.—In consequence, there are more organizational levels than reflected in the twoTroll types. The polytelic type comprises several degrees of truncation and homogenization, the basis for a reasonable organizational analysis should therefore be the degree of ramification of flowering branches rather than the mere question of a terminal flower on the main shoot axis (Fig. 6). On the other hand the three processes of truncation, homogenization and racemization are evolutionary transformations that may occur independently from one another, thus giving rise to a large number of variations, which can not be satisfactorily interpreted by exactly defined types. On the basis of these considerations the question of homologous parts in inflorescences is reviewed. The homology of partial florescences and paracladia is accentuated contrary toTroll's interpretation (Fig. 7). Homogenization as an evolutionary trend may transform paracladia of different degree of ramification, leading to one-flowered units on the one side and to highly complex structures as in theMarantaceae on the other.

     

Regulation of stem elongation in chinese cabbage by inflorescence removal and application of growth regulators

The effect of inflorescence removal on stem elongation in Chinese cabbage cv. Spring A was studied. Removal of the inflorescence before its visibility, or upon its appearance but before the beginning of bolting (stages 1–3), markedly reduced the stem length. Removal after the beginning of bolting (stage 5) had no effect on stem length. Application of GA₃ to the treated plants partially or fully restored the elongation of the flowering stem, whereas paclobutrazol inhibited the elongation of the treated, as well as the control stems. Indole-3-acetic acid (IAA) or kinetin was ineffective in restoring stem elongation of the plants from which the inflorescence had been removed. Inflorescences at stages 1–2 were found to secrete about 10 times more gibberellic acid (GA)-like activity compared with control apices or inflorescences at stage 5. It is suggested that the developing inflorescence is the major source of GAs which control stem elongation. However, shortly after the appearance of the inflorescence at the onset of bolting, stem elongation is no longer dependent on GAs derived from the apical inflorescence but require GAs from other sources.     

Competition for assimilates and fruit position affect fruit set in indeterminate greenhouse tomato

Localization and characterization of fruit set in winter tomato crops was investigated to determine the main internal and external controlling factors and to establish a quantitative relationship between fruit set and competition for assimilates. Individual fruit growth and development was assessed on a beef tomato cultivar during the reproductive period (first nine inflorescences). A non-destructive photograph technique was used to measure fruit growth from very early stages of their development and then calliper measurements were made on big fruits. From these measurements we determined the precise developmental stage at which fruit growth stopped. Fruit potential growth, which is defined as the growth achieved in non-limiting conditions for assimilate supply, was also assessed by this method on plants thinned to one flower per inflorescence. The latter was used to calculate the ratio between actual and potential growth, which was found to be a good index of the competition for assimilates. Time lags of fruit set were observed mainly on distal organs. When more than three flowers were left on each inflorescence, distal organs developed at the same time as proximal organs of the following inflorescence. Consequently they were submitted to a double competition within one inflorescence and among inflorescences. It was shown that, what is commonly named 'fruit set failure', is not an irreversible death of the organ and that a small fruit could resume growth after a delay of several weeks as soon as the first fruits ripened and thus ceased to compete for assimilates. In that case proximal fruits resumed growth before distal ones. The delayed fruits contained only few seeds but a germination test confirmed that fertilization took place before fruit set failed. Competition for assimilates was calculated during plant development by the ratio between actual and potential fruit growth. Potential growth of proximal fruits was strongly dependent on the position of the inflorescence on the stem, whereas potential growth of distal fruits was lower than or equal to that of proximal fruits of the same inflorescence and it was independent on the inflorescence position. We took into account both inflorescence and fruit positions to establish a quantitative relationship between fruit set of individual inflorescences and the ratio between actual and potential fruit growth.     

An assessment of morphogenetic fluctuation during reproductive phase change in Arabidopsis

Background and Aims

Reproductive phase change in Arabidopsis thaliana is characterized by two transitions in phytomer identity, the differentiation of the first elongate internode (bolting transition) and of the first flower (floral transition). An evaluation of the dynamics of these transitions was sought by examining the precision of the corresponding phytomer identity changes.

Methods

The length of the first elongate internode and the frequency of chimeric inflorescence structures, e.g. paraclades not subtended by a leaf (no-leaf/paraclades) and flowers subtended by a bract (bract/flowers), were measured in the Wassilewskija (Ws) accession and 47 early flowering mutants under a wide range of photoperiods. The impact of photoperiodic perturbations applied to Ws plants at different times of development was also evaluated.

Key Results

In Ws, both types of characters were remarkably constant across photoperiods in spite of a high degree of interindividual variability. Bract/flowers were not normally produced in Ws, but they were observed in conditions that suggest enhanced light signalling, e.g. in response to continuous light perturbations and in mutants with reduced hypocotyl elongation. In contrast, no-leaf/paraclades were normally present in approx. 20 % of Ws plants, and their frequency was increased in conditions that suggest reduced light signalling, e.g. in mutants with altered specification of long-day responses. The length of the first elongate internode was unrelated to the rate of stem elongation and to the regulation of reproductive phase change.

Conclusions

Bract/flowers and no-leaf/paraclades corresponded to opposite effects on the floral transition that reflected different dynamics of progression to flowering. In contrast, the length of the first elongate internode was only indirectly related to the regulation of reproductive phase change and was mainly dependent on global morphogenetic constraints. This paper proposes that morphogenetic variability could be used to identify critical phases of development and characterize the canalization of developmental patterns.     

Regulation of stem elongation in chinese cabbage by inflorescence removal and application of growth regulators

The effect of inflorescence removal on stem elongation in Chinese cabbage cv. Spring A was studied. Removal of the inflorescence before its visibility, or upon its appearance but before the beginning of bolting (stages 1–3), markedly reduced the stem length. Removal after the beginning of bolting (stage 5) had no effect on stem length.Application of GA₃ to the treated plants partially or fully restored the elongation of the flowering stem, whereas paclobutrazol inhibited the elongation of the treated, as well as the control stems. Indole-3-acetic acid (IAA) or kinetin was ineffective in restoring stem elongation of the plants from which the inflorescence had been removed. Inflorescences at stages 1–2 were found to secrete about 10 times more gibberellic acid (GA)-like activity compared with control apices or inflorescences at stage 5.It is suggested that the developing inflorescence is the major source of GAs which control stem elongation. However, shortly after the appearance of the inflorescence at the onset of bolting, stem elongation is no longer dependent on GAs derived from the apical inflorescence but require GAs from other sources.Contribution from the Agricultural Research Organization, The Volcani Center Bet Dagan, Israel No. 2218-E, 1987 series.     

Types of enrichment axes in Poaceae

The objective of this review work is to characterize the enrichment axes in Poaceae, especially integrating into that analysis of those species with basal or subterranean cleistogamous spikelets. We recognize five types of enrichment axes: paraclades of the unit of inflorescence (UIF), paraclades of the trophotagma (TT) with exposed UIF; paraclades of the trophotagma with not exposed UIF; subterranean paraclades on short rhizomes and subterranean paraclades upon plagiotropic axes of long internodes. According to the enrichment axes, we differentiate six types of synflorescences. The different types of enrichment axes and synflorescences types are characterized; their differences determine in some cases the existence of fruit heteromorphism.     

Analysis of inflorescence organogenesis in eastern gamagrass, Tripsacum dactyloides (Poaceae): the wild type and the gynomonoecious gsf1 mutant

Inflorescence organogenesis of a wild-type and a gynomonoecious (pistillate) mutant in Tripsacum dactyloides was studied using scanning electron microscopy. SEM (scanning electron microscope) analysis indicated that wild-type T. dactyloides (Eastern gamagrass) expressed a pattern of inflorescence organogenesis that is observed in other members of the subtribe Tripsacinae (Zea: maize and teosinte), family Poaceae. Branch primordia are initiated acropetally along the rachis of wild-type inflorescences in a distichous arrangement. Branch primordia at the base of some inflorescences develop into long branches, which themselves produce an acropetal series of distichous spikelet pair primordia. All other branch primordia function as spikelet pair primordia and bifurcate into pedicellate and sessile spikelet primordia. In all wild-type inflorescences development of the pedicellate spikelets is arrested in the proximal portion of the rachis, and these spikelets abort, leaving two rows of solitary sessile spikelets. Organogenesis of spikelets and florets in wild-type inflorescences is similar to that previously described in maize and the teosintes. Our analysis of gsf1 mutant inflorescences reveals a pattern of development similar to that of the wild type, but differs from the wild type in retaining (1) the pistillate condition in paired spikelets along the distal portion of the rachis and (2) the lower floret in sessile spikelets in the proximal region of the rachis. The gsf1 mutation blocks gynoecial tissue abortion in both the paired-spikelet and the unpaired-spikelet zone. This study supports the hypothesis that both femaleness and maleness in Zea and Tripsacum inflorescences are derived from a common developmental pathway. The pattern of inflorescence development is not inconsistent with the view that the maize ear was derived from a Tripsacum genomic background.     

Inflorescence structure in species of Scleria subgenus Hypoporum and subgenus Scleria (Sclerieae-Cyperaceae)

The objective of this study was to realize a typology approach toward the inflorescences in Scleria in order to provide characters that would have potential use in further taxonomic and phylogenetic research and that would allow identification of the tendencies and processes that could have yielded the variations within Scleria inflorescences. The majority of species studied present a main florescence; Scleria reticularis and S. melanomphala have truncated inflorescences. The variations are related to the grade of development reached by the main florescence and the different parts of the paracladial zone. Major inflorescence variability was found in section Scleria. A change in spikelet sexuality can occur toward the distal parts. There were variations in the distinct species with respect to the hierarchy of the paracladia where the change occurs. Future investigations should center on the ontogenetic aspects of inflorescence development of Scleria, integrating these results, together with those of adult inflorescences, into taxonomic and phylogenetic investigations.     

Inflorescence patterns in the woody Brazilian genus Diplusodon (Lythraceae)

The Brazilian genus Diplusodon is the second largest genus within Lythraceae. Their 85 species occupy diverse habitats within the ‘cerrado’ vegetation, and range from shrubs and treelets to dwarf, xylopodium-bearing subshrubs. A comparative-morphological survey of their inflorescence structures using Trollian typology is here presented, as well as some evolutionary considerations drawn from mapping inflorescence characters onto a preliminary phylogeny. The inflorescences of Diplusodon are mostly polytelic, ranging from single racemes to more or less complex double-, triple-, and multiple-racemes. Frondose, compound racemes are plesiomorphic within the genus. Nevertheless, an array of derived features has been found among their species, including production of lateral cymes, proliferation of the main axis, diverse patterns of internode elongation, reduction of subtending leaves to bracts, development of accessory branches, paedomorphic flowering, and, in three species, reversion to monotely.     

Geitonogamy in rewarding and unrewarding inflorescences: modelling pollen transfer on actual foraging sequences

Many orchid species are unusual in that they provide no nectar or pollen rewards for their pollinators. Absence of reward is expected to have a fundamental effect on pollinator visitation patterns. In particular the number of flowers visited per inflorescence is expected to be affected in both unrewarding and co-flowering rewarding species. We used arrays of artificial inflorescences, which could be either rewarding or unrewarding and were differentiated by their colour, to test how many flowers bumblebees visit in each type of inflorescence. The frequency of the two colours was varied, thus modelling the case where different frequencies of both an unrewarding and rewarding species were present in a patch. We found that bumblebees visited more flowers per rewarding inflorescence after they have experienced unrewarding or partially emptied rewarding inflorescences. We used these results to simulate pollen transfer and thus predict selfing rates on rewarding inflorescences. We found these increased when nectar depleted or when there was a greater proportion of unrewarding inflorescences in the patch. Conversely, we found that the number of flowers bumblebees visited on each unrewarding inflorescence did not significantly change through experiments. Selfing rates for unrewarding inflorescences were predicted to depend principally on the number of these inflorescences bumblebees visited rather than on the number of flowers they visit per inflorescence. This was because most visitors to orchids are supposed to be naive, and pollinators that commence foraging carrying no pollen will necessarily self any flower they pollinate on the first inflorescence they visit. Thus the average selfing rate is expected to increase as the sequence of inflorescences visited decreases in length.     

Diversity of inflorescences in the Boutelouinae subtribe (Poaceae: Chloridoideae: Cynodonteae)

The Boutelouinae subtribe is comprised of one monophyletic genus, Bouteloua, with 57 species inhabiting the semi-arid regions of the New World. The inflorescences show significant structural variations, which provides an interesting system to examine their morphological evolution and identify characters and processes that may help to understand the group systematics. The structure of inflorescences was studied in 25 species of Bouteloua. All the species covered under this study have truncated polytelic inflorescences. Structural variations in the inflorescence unit among species may be accounted for by: (1) symmetry of the inflorescence unit, (2) total number of long primary branches, (3) total number of spikelets per branch, (4) number of perfect flowers per spikelet, (5) number of rudimentary flowers, and (6) reproductive system. Homogenization and truncation processes account for the diversity of mature inflorescences that exists in Bouteloua. In this work, we discuss the systematic and taxonomic value of the inflorescence in the Boutelouinae subtribe.     

荒漠植物准噶尔无叶豆结实、结籽格局及其生态适应意义

连续2a采用野外记录的方式对荒漠植物准噶尔无叶豆的结实、结籽格局进行了比较研究。结果表明:植株内花序生成格局表现为不同大小的花序在总花序中的比重与其结实率存在显著正相关,其中含有中等花数目的花序所占的比重及其结实率均最高,此种分布格局能够最大程度的保证繁殖成功;果序内果实生成格局表现为单花着生位置(从近柄端算起)与其结实量占总结实量的比例成线性负相关,花序基部的结实比例最高,顶部结实比例近为0;荚果内种子生成格局表现为:中间位置的胚珠败育率最低。另外,年际间荚果内仅有(1.08±0.03)粒和(1.07±0.03)粒种子能够完全成熟,此种结籽格局是准噶尔无叶豆保证后代质量的最佳策略。     

The facultative photoperiodic response in the reproductive development of Amaranthus retroflexus L.: Changes in the dose response during ontogeny

The first inductive (short-day; SD) cycle advanced the initiation of reproductive development, while additional SD cycles progressively reduced the lag phase between the start of induction and initiation. The sensitivity to SD increased during ontogeny in long-days (LD) until even the requirement for the first SD cycle disappeared at the onset of autonomous flowering. In photo-induced plants, the postinitiation rate of elongation of the apex was accelerated as the SD dose was increased, but was progressively slower as the start of induction was delayed closer to autonomous flowering, approaching asymptotically the rate of non-induced controls. The inflorescences were branched in plants growing continuously in LD and unbranched in those growing continously in SD. The subsequent branching of the inflorescence could be repressed by SD at any time prior to autonomous flowering, and the degree of repression increased with the induction dose. After the initial SD cycle, 1–2 additional SD could induce the loss of apical dominance, causing excessive elongation and leaf production in the subjacent branches. Further increase in the SD dose inhibited this elongation by accelerating the transformation of the apices of these branches to the reproductive state.Abbreviations LD long day(s) - SD short day(s) - ContSD continuous short day(s) - RGR relative growth rate