Apical Rosettes Research Articles

Molecular characterisation of Pea seed borne mosaic poytvirus associated with apical rosette in field pea (Pisum sativum L.) in India

Symptoms of apical rosette were seen in field pea grown as winter season crop in India. Symptomatic leaves were processed for the identification of associated virus. The primers pair (PSbMV-F/PSbMV-R) targeting part of NIb gene of Pea seed borne mosaic potyvirus (PSbMV) was used in RT-PCR. The targeted fragment was successfully amplified cloned and sequenced. Sequencing of amplicons revealed it to be 795 bp long and identical to each other and hence only one was deposited to the NCBI database. Blast results of sequence showed it to be a portion of NIb region of the PSbMV and had 100–88.5% nt similarity with known isolates of the PSbMV. Phylogenetic analysis revealed that all the PSbMV isolates used group together. However, the PSbMV-IN:Knp isolate sub-clustered with the known PSbMV isolates of pathotype 1. This is the first report of the characterisation of an Indian isolate of PSbMV based on genomic sequence.

The Identity and Taxonomy of ×Sedeveria‘Blue Mist′ (Mottram) Gideon F.Sm. & Bischofb. (Crassulaceae)

We formally establish and clarify the application of the name ×Sedeveria ‘Blue Mist' (Mottram) Gideon F.Sm. & Bischofb., a cultivar selected from a hybrid between Sedum craigii R.T.Clausen and Echeveria affinis E.Walther (Crassulaceae). A similar hybrid was produced by Charles H. Uhl in the USA, but using Echeveria aff. affinis as one parent. We discuss ×Sedeveria ‘Blue Mist' in the context of Uhl's hybrid that was created for cytogenetics research purposes. ×Sedeveria ‘Blue Mist' is a small, rosulate to short-stemmed plant with visually striking blue-purple leaves and more or less uniformly bright crimson red flowers reminiscent of those of E. affinis, at least colour-wise. With age the flowers fade to whitish, a floral colour associated with S. craigii. Plants very slowly branch from the base, with the branches being leaning to creeping. The boatshaped, tapering, though often nearly cylindrical leaves of this cultivar are borne very densely in apical rosettes. The combination of these characters clearly separates this cultivar from other cultivars of ×Sedeveria E.Walther. The cultivar name ×Pachyveria ‘Blue Mist’ Mottram was previously published for the cultivar.

Echeveria ‘African Sunset’ Gideon F.Sm. & Figueiredo (Crassulaceae), a new cultivar from South Africa

A new cultivar of Echeveria DC. (Crassulaceae), E. ‘African Sunset’ Gideon F.Sm. & Figueiredo, is described from cultivation in South Africa. It is a small, rosulate to short-stemmed plant of unknown echeveria parentage. Echeveria ‘African Sunset’ has striking, light olive green foliage and its flowers are uniformly bright crimson red. Plants very slowly branch from the base, with the branches remaining leaning to creeping. The boat-shaped leaves of this cultivar are borne densely in apical rosettes. The combination of these characters clearly separates this cultivar from other Echeveria cultivars.

The cultivar ×Graptoveria ‘Fantome’ Aubé ex Gideon F.Sm. & Bischofb. is the most Commonly Cultivated Representative of the Crassulaceae in Southern Africa

The most commonly cultivated member of the Crassulaceae in southern Africa is a hybrid between representatives of the genera Graptopetalum Rose and Echeveria DC., in the nothogenus ×Graptoveria Gossot. However, to date there has been doubt as to the name that should be applied to this hybrid. Plants form distinct stems that are unable to retain the rosettes in an erect position, so becoming pendent, or creeping when grown on flat ground. The leaves of this ×Graptoveria are borne in dense, apical rosettes, have an obovate-spathulate shape, and are sometimes obscurely keeled. They are light glaucous-grey and pink-infused in full sun, and the margin is a lighter, whitish blue colour. The flowers are light yellow, with the central section of the petals longitudinally light greenish infused. The combination of these characters clearly separates this hybrid from any Crassulaceae taxa indigenous to southern Africa. The parentage of the hybrid has been postulated as E. elegans Rose and G. paraguayense (N.E.Br.) E.Walther. This hybrid is exceedingly common in southern African horticulture; however, it has not become invasive after many decades of cultivation, and shows no signs of becoming problematical. The history and nomenclature applicable to the hybrid are clarified, and the cultivar name ×Graptoveria ‘Fantome’ Aube ex Gideon F.Sm. & Bischofb. is established for it.

Basolateral protrusion and apical contraction cooperatively drive Drosophila germ-band extension.

Throughout development, tissues undergo complex morphological changes, resulting from cellular mechanics that evolve over time and in three-dimensional space. During Drosophila germ-band extension (GBE), cell intercalation is the key mechanism for tissue extension, and the associated apical junction remodelling is driven by polarized myosin-II-dependent contraction. However, the contribution of the basolateral cellular mechanics to GBE remains poorly understood. Here, we characterize how cells coordinate their shape from the apical to the basal side during rosette formation, a hallmark of cell intercalation. Basolateral rosette formation is driven by cells mostly located at the dorsal/ventral part of the rosette (D/V cells). These cells exhibit actin-rich wedge-shaped basolateral protrusions and migrate towards each other. Surprisingly, the formation of basolateral rosettes precedes that of the apical rosettes. Basolateral rosette formation is independent of apical contractility, but requires Rac1-dependent protrusive motility. Furthermore, we identified Src42A as a regulator of basolateral rosette formation. Our data show that in addition to apical contraction, active cell migration driven by basolateral protrusions plays a pivotal role in rosette formation and contributes toGBE.

Chlorophytum cremnophilum (Anthericaceae), a new caulescent succulent cliff-hanger from the Eastern Cape (RSA)

Summary: Chlorophytum cremnophilum (Anthericaceae) is a cremnophilous species only known from the Grootrivierspoort and the Kougarivier in the Eastern Cape is named. This new species is at once recognised by its drooping stems of up to a meter and more in length, usually sparingly dichotomously branched, with the apical rosettes turning upwards.

Spiral cleavage and early embryology of a loxosomatid entoproct and the usefulness of spiralian apical cross patterns for phylogenetic inferences

BackgroundAmong the four major bilaterian clades, Deuterostomia, Acoelomorpha, Ecdysozoa, and Lophotrochozoa, the latter shows an astonishing diversity of bodyplans. While the largest lophotrochozoan assemblage, the Spiralia, which at least comprises Annelida, Mollusca, Entoprocta, Platyhelminthes, and Nemertea, show a spiral cleavage pattern, Ectoprocta, Brachiopoda and Phoronida (the Lophophorata) cleave radially. Despite a vast amount of recent molecular phylogenetic analyses, the interrelationships of lophotrochozoan phyla remain largely unresolved. Thereby, Entoprocta play a key role, because they have frequently been assigned to the Ectoprocta, despite their differently cleaving embryos. However, developmental data on entoprocts employing modern methods are virtually non-existent and the data available rely exclusively on sketch drawings, thus calling for thorough re-investigation.ResultsBy applying fluorescence staining in combination with confocal microscopy and 3D-imaging techniques, we analyzed early embryonic development of a basal loxosomatid entoproct. We found that cleavage is asynchronous, equal, and spiral. An apical rosette, typical for most spiralian embryos, is formed. We also identified two cross-like cellular arrangements that bear similarities to both, a "molluscan-like" as well as an "annelid-like" cross, respectively.ConclusionsA broad comparison of cleavage types and apical cross patterns across Lophotrochozoa shows high plasticity of these character sets and we therefore argue that these developmental traits should be treated and interpreted carefully when used for phylogenetic inferences.

Galling by Rhopalomyia solidaginis alters Solidago altissima architecture and litter nutrient dynamics in an old-field ecosystem

Plant–insect interactions can alter ecosystem processes, especially if the insects modify plant architecture, quality, or the quantity of leaf litter inputs. In this study, we investigated the interactions between the rosette gall midge Rhopalomyia solidaginis and tall goldenrod, Solidago altissima, to quantify the degree to which the midge alters plant architecture and how the galls affect rates of litter decomposition and nutrient release in an old-field ecosystem. R. solidaginis commonly leads to the formation of a distinct apical rosette gall on S. altissima and approximately 15% of the ramets in a S. altissima patch were galled (range: 3–34%). Aboveground biomass of galled ramets was 60% higher and the leaf area density was four times greater on galled leaf tissue relative to the portions of the plant that were not affected by the gall. Overall decomposition rate constants did not differ between galled and ungalled leaf litter. However, leaf-litter mass loss was lower in galled litter relative to ungalled litter, which was likely driven by modest differences in initial litter chemistry; this effect diminished after 12 weeks of decomposition in the field. The proportion of N remaining was always higher in galled litter than in ungalled litter at each collection date indicating differential release of nitrogen in galled leaf litter. Several studies have shown that plant–insect interactions on woody species can alter ecosystem processes by affecting the quality or quantity of litter inputs. Our results illustrate how plant–insect interactions in an herbaceous species can affect ecosystem processes by altering the quality and quantity of litter inputs. Given that S. altissima dominates fields and that R. solidaginis galls are highly abundant throughout eastern North America, these interactions are likely to be important for both the structure and function of old-field ecosystems.

Plasmodium Vivax: Freeze-Fracture Studies on the Ultrastructure of the Sporozoites within the Salivary Gland of the Mosquito Anopheles Stephensi

Freeze-fracturing has been used to study the ultrastructure of the sporozoites of the malarial parasite Plasmodium vivax within the salivary gland of the mosquito Anopheles stephensi. The architecture of the pellicular complex of the salivary gland sporozoites was essentially the same as that reported for the intraoocystic forms, but the outline of cross-fractured P. vivax sporozoites was more flattened and crescent shaped as opposed to the circular outline described for the intraoocystic sporozoites. The salivary gland sporozoites of P. vivax also exhibited apical rosettes and a cytosome connected to a food vacuole, two unique structures not previously reported for malarial sporozoites.

Effects of Air Contact on Growth, Inorganic Carbon Sources, and Nitrogen Uptake by an Amphibious Freshwater Macrophyte.

Callitriche cophocarpa Sendtner is a heterophyllous amphibious macrophyte that produces apical rosettes of floating leaves. The importance of air contact for inorganic carbon and N uptake and for growth was investigated. Plants were grown with the floating rosette in contact with air of various humidities (10, 50, and >90% relative humidity) and with the submerged parts in N-free water at 350 [mu]M free CO2 and the roots in sediment with low or high NH3-N content. Humidity greatly affected the transpiration rate, whereas growth rate and N content were unaffected and were comparable to values measured for fully submerged shoots. Air contact had, however, a significant impact on growth when the free CO2 concentration in the water was low. Thus, the growth rate of shoots with air contact was about 3 times faster than the rate of fully submerged shoots when grown at air-equilibrium concentration of dissolved free CO2 in the water (16 [mu]M). This difference decreased with increased dissolved free CO2 concentration in the water, and the two shoot types grew at the same rate when the submerged shoots received >350 [mu]M free CO2. The quantitative importance of the floating rosette for total carbon uptake declined also with decreased ratio of floating rosette to total shoot weight. It is concluded that floating rosettes can enhance the inorganic carbon uptake of Callitriche. In contrast, air contact is of minor importance for nutrient transport.

Freeze fracture study of the pellicle of an Eimerian sporozoite (Protozoa, Coccidia)

Freeze fracture of Eimeria nieschulzi sporozoites reveals the structure of their three-membranous pellicle. The plasmalemma has an almost completely random distribution of intramembranous particles (IMP) but shows an apical rosette which may have a function in host cell penetration. The inner membrane complex is made of 13 longitudinal strips inserted on an apical truncated conical cap. Transverse sutures are present in the strips, as well as micropores. The two membranes have a similar, but back-to-back organization, which confirms the vesicular origin of the complex. The P faces bear very regular parallel alignments of IMP, with two dense lines per strip which might correspond with the underlying subpellicular microtubules (the number of which is twice the one of strips). The E faces are almost devoid of particles. The structural and functional significance of those findings are discussed.

Phylogeny and Ontogeny of Charophyta: ABSTRACT

The oldest known occurrence of the Charophyta is from the Devonian of eastern Europe. Devonian and Lower Mississippian rocks also contain the most diverse types of charophytes but their pre-Devonian ancestors are still unknown. During the Devonian the dextrally spiralled forms of the Trochiliscaceae increased in size, the number of spiral units decreased, and calcium carbonate was first secreted in coronula cells. Some workers believe that the reticulate forms of the Sycidiaceae and vertically ribbed forms of the Chovanellaceae are related closely and represent utricula. In the Middle Pennsylvanian through middle Permian are found the sinistrally spiralled forms with apical pores and hollow spirals of Stomochara Grambast. Palaeochura Bell has six spirals and is the only post-Devonian form of that type with the exception of some modern types. The upper Permian and Triassic contain forms not End_Page 526------------------------------ fundamentally unlike their Pennsylvanian ancestors. The apical pore, which was probably the germination point, was retained. Beginning in Late Jurassic and continuing through the Recent, conditions were more favorable throughout the world for charophyte growth and many different forms evolved. The utricle coverings of the gyrogonite, apical rosettes, peripheral groves, thinned apical areas, basal structures, nodes, and variations in structure of the spiral units evolved as their abundance apparently increased and ecologic niches became more abundant and varied. The ontogeny of the Tertiary forms also reflects this change. There is some enigma about the modern types because they are not as diverse as one might expect with the modern geologic setting of high continents and abundance of fresh- and brackish-water environments. Large collections containing many variations of growth stages are of greatest importance in the study of phylogenetic and ontogenetic characters. Because of this, selection of types commonly is misleading in taxonomic studies of the Charophyta. End_of_Article - Last_Page 527------------

EMBRYOLOGICAL DEVELOPMENT OF THE POLYCHAETOUS ANNELID, DIOPATRA CUPREA (BOSC)

1. Larvae of Diopatra cuprea (Bosc) have been raised, following artificial fertilization, to a stage with seven sets of setae. Observations on living stages and also on fixed and stained preparations have been described and photographed.2. Cell lineage studies have not been made, but observations indicate that the early cleavages are typical of those for spiral cleavage and that the ciliated stage (age, three hours) has a typical annelid cross and apical rosette. It, therefore, seems justifiable to conclude that the development of Diopatra cuprea follows the typical spiral pattern and mosaic development characteristic of other polychaetous annelids.3. Peculiarities of the development of this polychaete, and possibly of closely related species, are the following: the peculiar algal-like nurse cells attached to the developing oocyte (also characteristic of Onuphis eggs) when floating free in the coelom, the amazing rapidity of development to the free-swimming stage (three hours), the four plates of cells which appear to develop from cells of the prototroch and their peculiar posterior extensions into at least four plates of yolk spheres, and the asymmetry of the maxillary plates.4. Very little can be found in the literature on the embryology of the genus, Diopatra, and at least two authors have pointed out the possibility of error as to species in the identification of the developmental stages. Evidence is presented here which indicates that the early embryological and larval stages described by other investigators have been erroneously assigned to Diopatra cuprea.5. If the above is correct—and it would appear that Diopatra cuprea is the only onuphid found intertidally in the Woods Hole area—one may conclude that the investigation presented by the writer is probably the only study recorded in the literature on the early developmental stages of Diopatra cuprea (Bosc). This is exclusive of Monro's description of the later (post-larval) stage which, if not belonging to D. cuprea, is undoubtedly closely related to this species.