Reticulate Tectum Research Articles

Evolution of Angiosperm Pollen. 7. Nitrogen-fixing Clade

Nitrogen-fixing symbiosis in root nodules is known in only 10 families, which are distributed among a clade of four orders and delimited as the nitrogen-fixing clade. As the seventh in a series that examines pollen morphological distribution and evolution in the angiosperms, this paper focuses on pollen morphological character states of the nitrogen-fixing clade. To illustrate the palynological diversity of the clade, we first examined pollen grains from 26 species with light electron, scanning electron, and transmission electron microscopy. Second, we used a reduced data matrix from Li et al. (2015) to reconstruct a maximum likelihood tree and then optimized 18 pollen character states onto the tree using Fitch parsimony, maximum likelihood, and hierarchical Bayesian inference. Finally, 12 plesiomorphic states for the nitrogen-fixing clade were inferred unambiguously under all methods, and more than 40 clades (or lineages) at or above familial level were characterized by unambiguous pollen character state changes in at least one of the optimizations. We found a number of evolutionary trends for changes in pollen character states. These include increasing grain size, increasing aperture number accompanied by concomitant changes in aperture position (from equatorial to global) and aperture shape (from colpate to colporate), and increasing complexity of tectum ornamentation. There was a strong correlation between some pollen characters (prolate shape class, lobe outline in polar view, colpate ectoaperture, lalongate and lolongate endoaperture, absent supratectal element, reticulate tectum) and insect pollination, while other pollen characters—simple aperture structure, porate ectoaperture, circular endoaperture, present and gemmate or echinate supratectal element, and imperforate tectum—were strongly correlated with wind pollination. In addition, rugulate tectum was significantly correlated with shrub habit while larger pollen size was significantly correlated with vine habit; the helophytic habitat was significantly correlated with having two apertures. Our study provides rich evidence for the phylogenetic significance of pollen morphological diversity in the nitrogen-fixing clade.

Evolution of Angiosperm Pollen. 5. Early Diverging Superasteridae (Berberidopsidales, Caryophyllales, Cornales, Ericales, and Santalales) Plus Dilleniales

This study, the fifth in a series investigating palynological characters in angiosperms, aims to explore the distribution of states for 19 pollen characters on five early diverging orders of Superasteridae (Berberidopsidales, Caryophyllales, Cornales, Ericales, and Santalales) plus Dilleniales. To illustrate the character states found in the pollen of this group, we examined pollen grains of 15 species exemplifying 15 families across all studied orders using light, scanning, and transmission electron microscopy. We reconstructed the phylogeny of the early diverging Superasteridae and related taxa with eight genetic markers for 172 genera, using maximum likelihood (ML) analysis. Nineteen pollen characters were coded for the genera used in this phylogeny and compiled into two morphological matrices using two coding strategies. The characters were then optimized on the newly generated ML tree plus two constrained trees differing in the position of Dilleniales, using three methods of inference. Taxa in this grade show a striking diversity of pollen morphologies, particularly in certain characters such as size, tectum sculpture, and aperture number. The plesiomorphic condition for the early diverging Superasteridae is unambiguously and consistently inferred to comprise monad-dispersed, isopolar, spheroidal, circular in outline, equatorially arranged, tricolpate pollen grains with granular aperture membranes, a smooth tectum, and endexine present. We identify diagnostic character states and synapomorphies for several monophyletic groups, and explore the palynological evidence that may shed light on some unresolved relationships. For example, the hypothesis that Dilleniales is sister to Superrosidae is better supported than alternative hypotheses, being consistent with a number of shared palynological state changes including transitions to presence of costae, reticulate tectum, and columellar infratectum structure. Across this part of the angiosperm phylogeny, most state transitions occur repeatedly, and their frequency varies among both clades and characters. We discuss the impact of optimization method, tree topology, and coding strategy upon ancestral state reconstruction.

Pollen and seed morphology of Zygophylum fabago and Peganum harmala (Zygophyllaceae) from Bulgaria

Scanning electron microscope (SEM) study of the pollenand seed morphology of Peganum harmala L. and Zygophyllumfabago L. (Zygophyllaceae), in native Bulgarian populations, wascarried out. Additionally, a light microscope (LM) investigation onpollen grains was made in order to elucidate the peculiarities of themajor parameters of pollen surface and size. It was established thatpollen grains in Z. fabago are pantoporate. Exine ornamentation isreticulate. The pollen grains of P. harmala are oblate, spheroidal, elongated,oval in shape, colporate, exine striato-rugulate. The seeds of P.harmala are oblong-oval and slightly flattened at the side (incorrecttetrahedral to rhomboid), with a peaked edge, arc-curve laterally. Theseed sculpture corresponds to the Tubular to Concave-type, whichis characterized by polygonal cells and reticulate tectum. The seedsof Z. fabago are oval-rhomboid in shape. The seed sculpture correspondsto Concave to Convex-type which is characterized with polygonalcells, ranging in size, with cuticular wax folds.

Palynological study of Nonea (Boraginaceae-Boragineae) in Iran

Nonea Medik. is a genus of the Boraginaceae tribe Boragineae, with approximately 35 species worldwide. Examination of their palynological characters supported the separation of taxa, which is usually based on morphological and micromorphological reproductive features. Pollen grains of 10 taxa representing three groups of taxa in Iran, the N. caspica group, the N. persica group and the N. lutea group were studied, but N. rosea and N. turcomanica were not included. The results differed from previous studies in Iran. The N. caspica group, including N. caspica, N. melanocar-pa, and N. diffusa has 5-6-zonocolporate pollen grains with a psilate-punctate tectum. The N. per-sica group, including, N. p. var. persica, var. suchtelenioides, and N. pulla have 4-zonocolporate pollen grains with a psilate-punctate tectum. Finally the N. lutea group, including N. lutea var. lu-tea and N. l. var. flavescens, have 5-zonocolporate pollen grains with a reticulate-micro reticulate tectum. N. rosea and N. turcomanica have 5-zonocolporate pollen grains with a scrobiculate tec-tum ? 2011 Progress in Biological Sciences. Vol. 1, No. 2, 36-43.

The genus Borassus (Arecaceae) in West Africa, with a description of a new species from Burkina Faso

Borassus akeassii Bayton, Ouedraogo & Guinko sp. nov. (Arecaceae) is described as a new species from western Burkina Faso in West Africa. It has been confused with the widely distributed African species B. aethiopum and more recently with the Asian B. flabellifer. However, it is distinguished by its glaucous, green leaves with weakly armed petioles and a characteristic pattern of lamina venation. The fruits have a pointed apex and are greenish when ripe, and the flowers of the pistillate inflorescence are arranged in three spirals. The pollen has a reticulate tectum and distinctive ornamentation. The distribution of B. akeassii is discussed and the status of the varieties of Borassus aethiopum (var. bagamojensis and var. senegalensis) is examined. (c) 2006 The Linnean Society of London.

A new species of Rhoicissus (Vitaceae) from Sekhukhuneland, South Africa

Rhoicissus sekhukhuniensis Retief, Siebert & A.E.van Wyk, a rare new species from South Africa, is described, illustrated and compared with other members of the genus. It is a scandent shrub, rarely a robust climber, the young growth with a dense indumentum of reddish brown hairs. The species is closely related to the simple-leaved R. tomentosa (Lam.) Wild & R.B.Drumm., from which it can be distinguished by trifoliolate leaves with coarsely toothed margins. Pollen grains are tricolporate with a reticulate tectum. R. sekhukhuniensis is endemic to the Sekhukhuneland region, a centre of plant endemism associated with ultramafic rocks (mainly norite, anorthosite and pyroxenite) of the Eastern Bushveld igneous Complex.

Pollen morphology, exine structure and systematics of Acalyphoideae (Euphorbiaceae): Part 2. Tribes Agrostistachydeae ( Agrostistachys, Pseudagrostistachys, Cyttaranthus, Chondrostylis), Chrozophoreae ( Speranskia, Caperonia, Philyra, Ditaxis, Argythamnia, Chiropetalum, Doryxylon, Sumbaviopsis, Thyrsanthera, Melanolepis, Chrozophora), Caryodendreae ( Caryodendron, Discoglypremna, Alchorneopsis), Bernardieae ( Bernardia, Necepsia, Paranecepsia, Discocleidion, Adenophaedra) and Pycnocomeae ( Pycnocoma, Droceloncia, Argomuellera, Blumeodendron, Podadenia, Ptychopyxis, Botryophora)

This is the second paper of an extensive study of pollen morphology and exine structure of Acalyphoideae (Euphorbiaceae) following the most recent system of Webster. Part 2 describes the pollen of 30 genera assigned to tribes Agrostistachydeae, Chrozophoreae, Caryodendreae, Bernardieae and Pycnocomeae. In Agrostistachydeae, members of Agrostistachys and Pseudagrostistachys have similar but unspecialized pollen; grains of Cyttaranthus have weakly suprareticulate tecta of widely varying thickness and small densely spaced columellae; pollen of Chondrostylis has a croton sculpture and precisely defined bridges of ectexine over the endoaperture. Of the 11 genera assigned to tribe Chrozophoreae, pollen of Caperonia has prominent opercula, thick exines and punctate tecta, pollen of Ditaxis and Argythamnia is colpate, has large columellae, and the unevenly thick and complete tecta associated with suprareticulate sculpture or derivations thereof, and pollen of Chiropetalum has operculate apertures, diminutive columellae, and an incomplete finely reticulate tectum, characteristics which argue against a supposedly close relationship to Ditaxis and Argythamnia. Three of the four genera assigned to subtribe Doryxylinae, Doryxylon, Sumbaviopsis, and Melanolepis have similar pollen — thin exines with irregular foot layers, and irregular short columellae, whereas pollen of the fourth genus, Thyrsanthera, has thicker exines with a well-defined foot layer and more elongate columellae. The eight examined species of Chrozophora have 6–9 aperturate pollen and robust exines; two species have punctate tecta and zonorate endoapertures; the remaining species have heterobrochate tecta and lolongate endoapertures. The three genera comprising Caryodendreae, Caryodendron, Discoglypremna and Alchorneopsis, have small 3-colporate pollen with punctate tecta. Pollen of the five genera assigned to tribe Bernardieae, Bernardia, Necepsia, Paranecepsia, Discocleidion and Adenophaedra is of a similar, but unspecialized type — a punctate, deeply punctate, or microreticulate tectum, small endoaperture, and usually a prominent margo. The present concept of tribe Pycnocomeae as comprising Pycnocoma, Droceloncia, Argomuellera, Blumeodendron, Podadenia, Ptychopyxis and Botryophora is not supported by the pollen data. Members of Pycnocoma have pollen with a derived exine structure — a conspicuously thick endexine throughout the grain, threadlike foot layers, and columellae reduced to a point on the proximal side of the tectal elements. The pollen data are somewhat ambiguous about a close relationship between Droceloncia and Argomuellera, the two remaining genera in the subtribe Pycnocominae. The genera allied as subtribe Blumeodendrinae, Blumeodendron, Podadenia, Ptychopyxis, and Botryophora, share pollen with short narrow colpi, a croton sculpture, and mostly irregular columellae.

Pollen morphology, exine structure and systematics of Acalyphoideae (Euphorbiaceae) Part 1. Tribes Clutieae ( Clutia), Pogonophoreae ( Pogonophora), Chaetocarpeae ( Chaetocarpus, Trigonopleura), Pereae ( Pera), Cheiloseae ( Cheilosa, Neoscortechinia), Erismantheae pro parte ( Erismanthus, Moultonianthus), Dicoelieae ( Dicoelia), Galearieae ( Galearia, Microdesmis, Panda) and Ampereae ( Amperea, Monotaxis)

This is the first paper of an extensive study of pollen morphology and exine structure of the Euphorbiaceae. To date, the pollen of more than 600 species has been examined, most of them in transmission electron microscopy as well as light microscopy and scanning electron microscopy. Pollen of Acalyphoideae, tribes Clutieae, Pogonophoreae, Chaetocarpeae, Pereae, Cheiloseae, Erismantheae pro parte, Dicoelieae, Galearieae, and Ampereae is described, documented by electron micrographs, and the systematic implications of the data are discussed. Almost all members of the above tribes have pollen that is 3-colporate in which the endoaperture frequently has well-defined polar margins but diffuse lateral ones. The tectum and exine structure are more variable. Pollen of Clutia has branched columellae and a tectum in which the ‘floors’ of the lumina are formed not by the foot layer but by the fusion of the distal tips of columellae. Pollen of Pogonophora has large columellae and a thick punctate tectum, characteristics that are shared with Trigonopleura, a genus assigned to Chaetocarpeae. The genus Chaetocarpus has pollen with small columellae and microrugulose tecta. Most species of Pera have thin exines characterized by small columellae; pollen of P. arborea is intectate; pollen of P. distichophylla is thick-walled with massive columellae and a thick foot layer-endexine. Grains of Cheilosa and Neoscortechinia (Cheiloseae) have echinate tecta, a distinction reinforced by an almost identical exine structure. The single species of Moultonianthus (Erismantheae) has pollen with reticulate tecta and well-developed columellae while Erismanthus has a punctate tectum and small irregular columellae. Pollen of Dicoelia has a weakly suprareticulate tectum and columellae that are poorly differentiated from a channeled tectum. Grains of Galearia and Microdesmis have thin exines with deeply punctate tecta in contrast to pollen of the third genus of Galearieae, Panda, which has a thick exine with and a reticulate tectum. The two genera of Ampereae, Amperea and Monotaxis, have pollen with reticulate tecta, but the former genus has large elongate columellae and partially covered lumina, and the latter has smaller columellae and an unmodified reticulate tectum. The data from exine structure: support the monogeneric concept of Clutieae; show that Pogonophora is not closely related to Clutia, suggest that Trigonopleura may be more closely related to Pogonophoreae than to Chaetocarpeae; are anomalously, sometimes conspicuously, variable within Pera; support the present concept of Cheiloseae and the close relationship between and the isolation of Cheilosa and Neoscortechinia; support a close relationship between Galearia and Microdesmis, but not with Panda; suggest that the biovulate genus Dicoelia is isolated in the uniovulate Acalyphoideae; and indicate that the similarity in SEM between pollen of Amperea and that of Monotaxis is superficial, and that the two genera are not as closely related as previously thought.

A new species of Cyphostemma (Vitaceae) from South Africa

Cyphostemma rubroglandulosum Retief & Van Wyk, a new species from South Africa, is described, illustrated and compared with other members of the genus in southern Africa. It is a climbing, succulent herb with conspicuous, red, multicellular, glandular hairs on the stems, leaves and inflorescences. The combination of glandular hairs, 3-foliolate leaves, and fruits with scattered, multicellular hairs distinguishes it from all other members of the genus in southern Africa. Pollen grains are 3-zonocolporate with a reticulate tectum; the closely spaced pores differ in shape and size. Associated with forest, C. rubroglandulosum is endemic to the Pondoland Centre, an acknowledged centre of endemism associated with Natal Group Sandstone (Msikaba Formation) in southern KwaZulu-Natal and parts of the adjacent Eastern Cape Province.

A Note on Remarkable Exines in Acalyphoideae (Euphorbiaceae)

As part of an extensive study of pollen of Euphorbiaceae that combines transmission electron microscopy with scanning electron microscopy, distinctive exines are reported and documented for certain Acalyphoideae. Cheilosa and Neoscortechinia, which comprise the tribe Cheiloseae, are the only Acalyphoideae with an echinate tectum, bur their apertures and exine structure do not support a relationship to Oldfieldioideae. In Ditaxis, one of the three mesocolpia is much smaller than the other two and the pollen can be easily distinguished from all other Euphorbiaceae. In SEM, the tectum of Pycnocoma appears almost complete, but in TEM the exine consists of irregular, mostly discrete rectal elements that narrow to points (=columellae) at the interface with the threadlike footlayer. The operculate grains of Alchornea and Boquillonia have exines with a poorly differentiated double layer of columellae in the mesocolpium, but nearer the endoaperture the lower tier becomes greatly elongated and appears to rest directly on the endexine. Plukenetia polyadenia has a complete tectum and a thick exine with a predominant infratectum of large, occasionally branched columellae that nearer the tectum are combined with densely spaced granules. Plukenetia penninervia has a reticulate tectum of crenate muri and short, sparse columellae. The pollen diversity in Acalyphoideae suggests that the subfamily, many tribes and even genera may not be monophyletic.

Tetrad pollen in the subfamily Caesalpinioideae (Leguminosae) and its significance

Pollen in permanent tetrads occurs in only eight species from three genera placed in widely separated tribes in the Caesalpiniodease. Tetrads are recorded in all four species of Diptychandra (including one yet to be described) in the tribe Caesalpinieae. They occur in only two species of about 300 in Bauhinia ( B. phoenicea and B. pottsii and its varieties) in the tribe Cercideae. Of 13 species of Afzelia in the tribe Detarieae tetrad pollen has been found only in A. pachyloba and A. bella and its varieties. There are few common features in the tetrad pollen found in the subfamily. Diptychandra has acalymate tetrads with distinctive interconnecting channels between individual grains. Bauhinia phoenicea has calymate pollen while B. pottsii has acalymate pollen with cross wall cohesion and exine bridges. There is a wide range of variation in the shape of the pollen, colpal length and ornamentation among the four varieties of B. pottsii. The tetrads are acalymate in Afzelia, held together by a shared tectum. The pollen has a thin endexine, very thin lamellated foot layer, short columellae and very thick, coarsely reticulate tectum, very distinct from the perforate tectum found in the other genera. The limited occurrence of tetrad pollen within the subfamily and the significance of its great variation in Bauhinia, and to a lesser extent in the other genera, is discussed. The range of structure and plasticity of arrangement of tetrads and their wide taxonomic distribution, suggest that these pollen structures arose more than once in the Caesalpinioideae and this might be expected in the subfamily which is regarded as ancestral in the Leguminosae.

Pollen Morphology of Two New East African Species of Fernandoa (Bignoniaceae)

The pollen morphology of two new East African species of Fernandoa, F. abbreviata and F. lutea, is described from light, scanning and transmission electron microscopy. The pollen morphology of the three other African species has also been examined. The pollen grains of all species examined are trizonocolpate, isopolar with long colpi and a reticulate tectum. The colpi, unusually, show more or less regular ruptures, usually two or three, in the acetolysis-resistant colpus membrane. Small differences between the pollen of the five species support recent taxonomic changes. The possible function and adaptive significance of this rare colpus type is discussed. New data are provided from transmission electron microscopy.

Pollen morphology ofpolyscias(araliaceae): the malesian and australian species

Abstract The pollen morphology of 33 Malesian and Australian taxa of Polyscias is described, and the variation assessed by multivariate analysis. The analysis identified two main pollen types: (1) relatively small grains with a microreticulate tectum and lalongate ora (sect. Polyscias, Gelibia, Eupteron and six taxa not assignable to any of the sections as they are currently defined, (2) relatively large grains with a reticulate tectum, or which do not possess a tectum (previously unknown in the family), lalongate, lolongate or circular ora (sect. Kissodendron and Palmervandenbroekia). The systematic utility of palynologial data at various taxonomic levels within Polyscias is dicussed.

The significance of some pollen morphological characters of the tribe Amorpheae and of the genus Mucuna (tribe phaseoleae) in the biology and systematics of subfamily Papilionoideae (Leguminosae)

Aperture configuration, tectal ornamentation and exine stratification are the most significant pollen characters in the subfamily Papilionoideae (Leguminosae). Some trends in pollen characters are closely correlated with trends towards specialisation in macromorphological characters. The structure of the colpate/colporate aperture and its associated aperture membrane/operculum is described in the tribe Amorpheae. Here the genera Apoplanesia, Eysenhardtia and most species of Errazurizia have small tricolporate pollen with a granular colpus membrane and complete tectum. The pollen of Amorpha, Parryella and one species of Errazurizia have tricolporate pollen with an operculum and reticulate tectum. Dalea, Marina and Psorothamnus have larger tricolpate, operculate, reticulate pollen. Some species of the genus Mucuna have pollen with a columellate interstitium while others have a granular interstitium. These types correspond in general with the proposed macromorphologically based division of the genus. Supratectal verrucate ornamentation occurs in some neotropical species of Mucuna. This pollen character appears to be related to floral morphology and pollinator.

A palynological study of the genushelleborus(ranunculaceae)

Abstract The pollen of 18 collections representing 11 species of Helleborus has been examined in LM and SEM, and a selected group in TEM. The pollen is 3‐colpate and has a finely or coarsely reticulate tectum in which the muri are colliculate, or, more rarely, a complete tectum which is sparsely colliculate and sparsely punctate. The three tectalmorphs probably represent a progression in the “degree of completeness” of the tectum and they are clearly related. They are, however, distinct from each other, and no intermediate forms were found that might have compromised the separation of the finely reticulate and coarsely reticulate tecta. The three tectalmorphs have an unequal distribution, the complete tectum was found in only one species (H. niger), the finely reticulate in four species, and the coarsely reticulate in six species. For the most part the pollen data reinforce existing infrageneric alignments. Palynologically, Helleborus can be distinguished from all remaining members of the Ranunculaceae, t...

Pollen morphology and taxonomy of the subtribe Diocleinae (Leguminosae: Papilionoideae: Phaseoleae)

The pollen morphology of the thirteen genera currently included in the subtribe Diocleinae is described. Nine pollen types with a number of subtypes are recognized. These are arranged into two main groups. The first comprises the macromorphologically anomalous genera Calopogonium, Herpyza and Pachyrhizus which, although united by some pollen characters, are distinct both from each other and from the rest of the subtribe. The second group, consisting of the remaining genera which can to some extent be distinguished from each other by their pollen morphology, nevertheless appear to make up both macromorphologically and palynologically a more natural Diocleinae. The six pollen types in the second group are further divided into two slightly overlapping subgroups. Luzonia and Macropsychanthus are palynologically somewhat distinct but, together with Dioclea and Canavalia, have generally rather large, oblate pollen grains with a complete or perforate tectum, in contrast with the pollen of the genera Camptosema, Collaea, Cratylia and much of Galactia which is smaller, spheroidal with a reticulate tectum. Dioclea has some species with isopolar pollen and others with heteropolar pollen grains and this more or less correlates with subgeneric divisions within the genus. Galactia from the Caribbean area has similar but much smaller pollen. The taxonomic significance of this parallel between the pollen morphology of Dioclea and Caribbean Galactia is unclear. The pollen of Canavalia appears to show no significant variation. A possible correlation between the pollen subgroups with ecological habitat and pollinators is discussed.

Pollen Morphology of the Tribe Triclisieae of the Menispermaceae in Relation to Its Taxonomy

Summary. The pollen morphology of 3 genera and 5 species comprising the tribe Coscinieae (Menispermaceae) has been studied. The pollen is small, 3-aperturate with a perforate or reticulate tectum. Two main pollen types are recognized (I) tricolporate found in the genera Anamirta and Arcangelisia and (2) triporate found in the genus Coscinium. Pollen morphology supports taxonomy by showing a closer relationship between Anamirta and Arcangelisia than with the more distinct genus Coscinium.