Basal Pores Research Articles

Effect of Heat Stress on Rice and Its Management

Rice is a major staple food, consumed by more than half of the world’s population and providing 20% of calories consumed worldwide. However, rice production is under serious threat due to rapid increase in the earth’s rising temperatures. Heat stress (HS) destroys the physiological processes like seed germination, photosynthesis, respiration and plant growth. HS also has detrimental effects on the plant root system that provides water uptake, nutrient uptake and supports other parts of the plant, leading to disruption of root growth and development, as well as decrease in shoot and root fresh, and dry weight. As a result there is a drastic reduction in the yield and quality of the grain. HS affects all the growth stages of rice. However, the reproductive phase of rice is more sensitive to HS than other stages. Most agronomic management approaches concentrate on early sowing, site-specific cropping and irrigation system changes, and adoption of a late or early maturing cultivar to avoid high temperatures during grain filling to combat HS. Growth regulators such cytokines, salicylic acid, and ethylene precursors can also be used to treat rice plants suffering from HS related damage such as pollen abortion, decreased spikelet’s per panicle and kernel weight, and low seed-setting rate. In numerous rice cultivars, exogenous treatment of spermidine boosted photosynthetic and antioxidant capability and partially reduced the yield penalty brought on by HS. Developing germplasm with higher tolerance to climate-induced stresses through breeding is a sound climate change or abiotic stresses adaptation strategy. Higher thermo-tolerance may be induced by choosing cultivars that flower in the early morning before the temperature rises and have larger anthers with long basal pores, higher basal dehiscence, and pollen viability. Breeding rice varieties tolerance to high temperature has so far received little attention as compared to other abiotic stresses like drought and salinity. Therefore, there is an urgent need to explore the breeding aspect for heat tolerance in rice varities for better management of loss due to heat stress.

Morphological factors associated with giant vacuoles with I-pores in Schlemm's canal endothelial cells of human eyes: A serial block-face scanning electron microscopy study

Increased intraocular pressure (IOP) is the main risk factor for primary open-angle glaucoma and results from impaired drainage of aqueous humor (AH) through the trabecular outflow pathway. AH must pass the inner wall (IW) endothelium of Schlemm's canal (SC), which is a monolayer held together by tight junctions, to exit the eye. One route across the IW is through giant vacuoles (GVs) with their basal openings and intracellular pores (I-pores). AH drainage through the trabecular outflow pathway is segmental. Whether more GVs with both basal openings and I-pores are present in the active flow areas and factors that may influence formation of GVs with I-pores have not been fully elucidated due to limitations in imaging methods. In this study, we applied a relatively new technique, serial block-face scanning electron microscopy (SBF-SEM), to investigate morphological factors associated with GVs with I-pores in different flow areas. Two normal human donor eyes were perfused at 15 mmHg with fluorescent tracers to label the outflow pattern followed by perfusion-fixation. Six radial wedges of trabecular meshwork including SC (2 each from high-, low-, and non-flow areas) were imaged using SBF-SEM (total: 9802 images). Total GVs, I-pores, basal openings, and four types of GVs were identified. Percentages of GVs with I-pores and basal openings and number of I-pores/GV were determined. Overall, 14.4% (477/3302) of GVs had I-pores. Overall percentage of GVs with both I-pores and basal openings was higher in high- (15.7%), than low- (12.6%) or non-flow (7.3%) areas. Of GVs with I-pores, 83.2% had a single I-pore; 16.8% had multiple I-pores (range: 2–6). Additionally, 180 GVs (90 with I-pores and 90 without I-pores) were randomly selected, manually segmented, and three-dimensionally (3D) reconstructed to determine size, shape, and thickness of the cellular lining. Size of GVs (including median volume, surface area, and maximal cross-sectional area) with I-pores (n = 90) was significantly larger than GVs without I-pores (n = 90) using 3D-reconstructed GVs (P ≤ 0.01). Most I-pores (73.3%; 66/90) were located on or close to GV's maximal cross-sectional area with significant thinning of the cellular lining. Our results suggest that larger size and thinner cellular lining of GVs may contribute to formation of GVs with I-pores. More GVs with I-pores and basal openings were observed in high-flow areas, suggesting these GVs do provide a channel through which AH passes into SC and that increasing this type of GV may be a potential strategy to increase aqueous outflow for glaucoma treatment.

Phylogenetic analyses confirm polyphyly of the genus Campanula (Campanulaceae s. str.), leading to a proposal for generic reappraisal

AbstractPrevious phylogenetic analyses found that the largest genus in the tribe Campanuleae, Campanula L. is polyphyletic. The genus is extremely intermingled, involving more than 50 genera, but no generic reappraisal has been attempted. For undertaking further phylogenetic analyses and subsequent generic reappraisal of the tribe, we sampled 333 samples, representing 27 of 28 genera currently recognized. Among them, 146 samples and two genera, Cylindrocarpa Regel and Sergia Fed., were newly sequenced. Six chloroplast DNA loci (atpB‐rbcL, matK, petD‐intron, rbcL, rpl16, and trnL‐F) and internal transcribed spacer were used to undertake phylogenetic analyses. Our chloroplast DNA phylogeny comprises 24 clades, that is, 18 Cam clades and six genera, Feeria Buser, Homocodon D. Y. Hong, Jasione L., Peracarpa Hook. f. & Thomson, Trachelium L., and Favratia Feer. Campanula species are scattered among the 18 Cam clades and the six genera, and some of them join with well‐established genera like Phyteuma L. and Adenophora Fisch. In the phylogeny Musschia Dumort. is at the basal position, but Jasione's position is unclear, whether in the tribe Campanuleae or in Wahlenbergieae; the other 22 lineages are grouped into two major clades: clade A comprising Cam 13–17 plus Feeria and Trachelium, and clade B comprising Cam 02, 03, 04‐1, 04‐2, and 06‐12 plus Homocodon and Peracarpa. We found that the molecular phylogeny is closely correlated with morphology, particularly pollen morphology: clade A with pollen 3‐porate and capsule dehiscent mostly by basal pores; and clade B with pollen mostly 4 (5–15)‐porate and capsule dehiscent mostly by apical‐middle pores. A generic reappraisal of the tribe is suggested based on the integrated phylogenetic analyses.

Oxygen Containing Carbon Materials for High Capacity and Fast Chargeable Anode Materials of Lithium Ion Batteries

The lithium-ion battery is the most promising energy storage devices for variety of applications from portable electronics to electric vehicles because of its high energy density, power density and cycle life. However, the upcoming boom for artificial intelligence (AI) assisted transportations, Internet of Things (IoT) or potential wireless financial technologies may require batteries with much higher energy density and fast chargeable capability. Silicon and silicon monoxide have been extensive investigated for high capacity anode for more than 10 years. However, they are still hard to be used in real practice because of large volumetric expansion, poor cycle life, and bad rate capability. On the other hand, graphite is the most popular commercialized anode material for Li-ion battery because of its excellent coulombic efficiency, long cycle life, low cost and ease of processing. However, the limited theoretical capacity (372 mAh/g) and small interlayer spaces (0.335 nm) made it difficult to be used in the application of Li-ion batteries with higher energy density and fast chargeable Li-ion batteries (Fig.1a). In this study, we have introduced a novel Graphene-Like-Graphite (GLG) anode material to be used in Li-ion batteries with higher capacity and good rate capability. According to the Li-NMR study, lithium ions can intercalate into graphene layers with oxygen at 0-1.2V (vs Li) with non-stage phenomenon and delivered a capacity more than 372mAh/g. Meanwhile, at a higher potential range from 1.2 to 2V (vs Li), lithium ions continuous react with oxygen containing functional groups reversibly on the basal plane of each graphene layer. As a result, the GLG could have an initial discharge capacity up to 608mAh/g which is much larger than conventional graphite (372mAh/g). It was investigated that the higher oxygen content offers a higher reversible capacity over 1.2V (vs Li) discharge. Atom resolution STEM is also carried out for the characterization of single layer graphene of the GLG. It was learned that the GLG graphene layer has pore structure with the size less than 2nm, moreover the oxygen containing functional groups were attached on both basal plane and pores` s edge. The GLG was also characterized with NCM111 cathode for full-cell rate capability and cyclability. The cell charged to 60% of the capacity up to 6C (10min) charge with 103wh/kg cell design, while have good cycle ability. XPS, HAXPES, C-NMR were also used for the characterization of the GLG materials. Finally, a structure model was proposed for the next generation high rate, high capacity carbon based anode materials. Figure 1

Microstructure provides insights into evolutionary design and resilience of Coscinodiscus sp. frustule

We conducted in situ three-point bending experiments on beams with roughly square cross-sections, which we fabricated from the frustule of Coscinodiscus sp. We observe failure by brittle fracture at an average stress of 1.1 GPa. Analysis of crack propagation and shell morphology reveals a differentiation in the function of the frustule layers with the basal layer pores, which deflect crack propagation. We calculated the relative density of the frustule to be ∼30% and show that at this density the frustule has the highest strength-to-density ratio of 1,702 kN⋅m/kg, a significant departure from all reported biologic materials. We also performed nanoindentation on both the single basal layer of the frustule as well as the girdle band and show that these components display similar mechanical properties that also agree well with bending tests. Transmission electron microscopy analysis reveals that the frustule is made almost entirely of amorphous silica with a nanocrystalline proximal layer. No flaws are observed within the frustule material down to 2 nm. Finite element simulations of the three-point bending experiments show that the basal layer carries most of the applied load whereas stresses within the cribrum and areolae layer are an order of magnitude lower. These results demonstrate the natural development of architecture in live organisms to simultaneously achieve light weight, strength, and exceptional structural integrity and may provide insight into evolutionary design.

Abstract 14619: Ultrasound-stimulated Microbubbles for Drug/gene Delivery: Microbubble-generated Shear Stress Induces Pores in Cellular Membranes

Background: Ultrasound (US)-stimulated microbubbles (MBs) are emerging as novel target-specific non-viral gene/drug delivery vectors for treatment of vascular disease, e.g. to deliver VEGF plasmid DNA to promote arteriogenesis. The nature of the MB-target cell interactions that facilitate nucleic acid delivery across cell membranes, and hence strategies to optimize the efficiency of this platform, are poorly understood. The objective of this study was to gain mechanistic insight into MB-mediated increases in cell membrane permeability. Methods: Phospholipid coated MBs were allowed to lay adjacent to cultured human umbilical vein endothelial cells (HUVEC) at 37C. Propidium iodide (PI) was put into the media before US exposure to assess membrane permeability (sonoporation). Individual MB-cell pairs (n=351) were exposed to a single US pulse at 0.5, 1, or 2 MHz, with a duration of 4, 8 or 16 μs and pressures 0.1-0.8 MPa. Ultrafast microscopy recorded MB oscillations (Fig. 1a); a second camera simultaneously recorded fluorescence (PI uptake, Fig. 1b). US-induced MB radius change (excursion) was measured and used to calculate shear stress. HUVEC membranes were fluorescently labeled to visualize pore features. Results: Absolute MB excursion distance and associated shear stress were strong threshold indicators of sonoporation (PI uptake). For an 8 μs pulse, the oscillation (shear stress) threshold above which HUVECs porate was 3.9, 2.6, and 1.4 μm (7.8, 14.5, 22.7 kPa) at 0.5, 1 and 2 MHz respectively. At a given US frequency, increases in pulse duration decreased the required excursion and shear stress. Cell membrane imaging showed that MBs can induce apical and basal pores (sub-μm to μm sizes) that reseal (Fig. 1c). Conclusions: Sonoporation is related to absolute MB excursion distance and its associated shear stress and can occur with various US parameters and MB sizes. This data has implications on intelligent US-MB design for their use as payload delivery vehicles.

Campanula teutana, a new isophyllous Campanula (Campanulaceae) from the Adriatic region

The Balkan Peninsula and the amphi-Adriatic region are biodiversity centres with a high number of Campanula species, some of them with restricted and isolated distributions. Among those is the morphologically, karyologically and genetically well-defined linage of isophyllous Campanula species of the garganica clade, taxonomically treated as Campanula ser. Garganicae. In the central Adriatic, on the Island of Vis (Croatia), an isophyllous Campanula was found growing in rocky crevices of calcareous sea cliffs among chasmophytic vegetation with extremely challenging ecological conditions. Based on morphological characters (monopodial growth form, cordate to ovate basal leaves, campanulate corolla, presence of obtuse hairs at the base of filaments, capsule opening by basal pores and brown shiny seeds) the unidentified plant from the Island of Vis falls into ser. Garganicae. To establish the phylogenetic position and relationships of the unknown Campanula among other species of the garganica clade, nuclear ITS and chloroplast trnL-F sequences as well as comparative morphology, karyology and scanning electron microscopy of seeds were used. Due to its campanulate corolla the plants from Vis are morphologically close to C. portenschlagiana from the eastern Adriatic, from which they differ in several quantitative floral characters. The karyological analysis revealed a diploid chromosome number (2n = 34), while SEM analysis showed that seed coat of new taxon has weakly striate testa, thin wavy striped radial walls and slightly marked lumen. Additionally, molecular data show that the Vis taxon is clearly separated as a distinct species from other species of ser. Garganicae. Therefore, it is described and illustrated as a new species, Campanula teutana Bogdanović & Brullo. Because of the small number of individuals within the single population, C. teutana should be included on the Red List of the vascular flora of Croatia as an endangered species (EN).

Functional structure of antennal sensilla in the myrmecophilous beetle Paussus favieri (Coleoptera, Carabidae, Paussini)

The evolution of a myrmecophilous lifestyle in beetles is often associated with morphological alterations. In particular, the antennae of all members of the myrmecophilous ground beetle tribe Paussini are greatly modified, with flagellomeres flattened or crassate, frequently reduced in number from 9 to 5 or even 1 single “antennal club”. The enhanced glandular function of the antennal club has been recently described by scanning (SEM) and transmission (TEM) electron microscopy in Paussus favieri Fairmaire, 1851, where the antenna has become a complex glandular organ, supplying rewarding substances to the ants. In the present work, the antennal sensilla of P. favieri are investigated by SEM, TEM and focused ion beam (FIB/SEM) technology. Most sensilla of scape and antennal club are highly modified mechanoreceptors (i.e. multipointed, fringed, branched, brush-like, sickle-shaped), singly or grouped in tufts (“antennal symphilous organs”). These “trichomes”, here assigned to 8 different morphotypes of sensilla chaetica (Ch.1–Ch.8), show a variable number of basal pores (present also at the base of the taste sensilla Ch.9), which spread dense substances of unknown chemical composition on the seta. Although hygro-, thermo- and chemoreceptors are reduced in number as compared with non-myrmecophilous relatives, and mainly relegated to the apex of the antennal club, their diversity is comparable to that of other carabid beetles: two types of sensilla trichodea (Tr.1–Tr.2); three types of basiconica (Ba.1–Ba.3); one type of campaniformia (Ca); one type of coeloconica (Co) and one type of Böhm sensilla (Bo). Contrary to the hypothesis that Paussus species lack a Johston's organ, a non-connective chordotonal organ composed of 9 groups of scolopidia has been found inside the pedicel. A comparison between sensilla of P. favieri and those of other non-myrmecophilous and myrmecophilous ground beetle species is provided.

Impact of high-temperature stress on rice plant and its traits related to tolerance

SUMMARYThe predicted 2–4°C increment in temperature by the end of the 21st Century poses a threat to rice production. The impact of high temperatures at night is more devastating than day-time or mean daily temperatures. Booting and flowering are the stages most sensitive to high temperature, which may sometimes lead to complete sterility. Humidity also plays a vital role in increasing the spikelet sterility at increased temperature. Significant variation exists among rice germplasms in response to temperature stress. Flowering at cooler times of day, more pollen viability, larger anthers, longer basal dehiscence and presence of long basal pores are some of the phenotypic markers for high-temperature tolerance. Protection of structural proteins, enzymes and membranes and expression of heat shock proteins (HSPs) are some of the biochemical processes that can impart thermo-tolerance. All these traits should be actively exploited in future breeding programmes for developing heat-resistant cultivars. Replacement of heat-sensitive cultivars with heat-tolerant ones, adjustment of sowing time, choice of varieties with a growth duration allowing avoidance of peak stress periods, and exogenous application of plant hormones are some of the adaptive measures that will help in the mitigation of forecast yield reduction due to global warming.

Characteristics of floral organs related to reliable self-pollination in rice (Oryza sativa L.).

In many varieties of rice, the length of basal pores on the thecae just after anthesis is strongly correlated both with the percentage of florets receiving adequate pollen and with the number of pollen grains deposited on the stigmata and its variation (coefficient of variation). Therefore, the size of the basal pores is considered to be an important factor for the reliable self-pollination of rice. We discuss how long basal pores may facilitate self- pollination.

Tetrahymena thermophila contains a conventional gamma-tubulin that is differentially required for the maintenance of different microtubule-organizing centers.

The gene (GTU1) encoding Tetrahymena thermophila gamma-tubulin was cloned and analyzed. GTU1 is a single-copy, essential gene encoding a conventional gamma-tubulin. HA-tagged GTU1p localizes to four microtubule-organizing centers (MTOCs) in vegetative cells: basal bodies (BBs), macronuclear envelopes, micronuclear envelopes, and contractile vacuole pores. gamma-Tubulin function was studied by placing the GTU1 gene under control of an inducible-repressible promoter. Overexpression of GTU1 had no detectable effect on cell growth or morphology. Depletion of gamma-tubulin resulted in marked changes in cell morphology and in MT bundling. MTOCs showed different sensitivities to gamma-tubulin depletion, with BBs being the most sensitive. gamma-Tubulin was required not only for the formation of new BBs but also for maintenance of mature BBs. BBs disappeared in stages, first losing gamma-tubulin and then centrin and glutamylated tubulin. When GTU1 expression was reinduced in depleted cells, BBs reformed rapidly, and the normal, highly organized structure of the Tetrahymena cell cortex was reestablished, indicating that the precise patterning of the cortex can be formed de novo.

First Report of Alternaria Leaf Spot of Almond Caused by Species in the Alternaria alternata Complex in California.

A new leaf spot disease of almond (Prunus dulcis [Mill.] D. Webb) was observed in California in the late 1980s and was first associated with severe defoliation in the mid-1990s (1). Orchards in areas with frequent summer dews, high humidity, and little air movement sustained severe defoliation, resulting in yield losses often exceeding 50%. Symptoms occur only on leaf blades in late spring and summer. Lesions develop as small, circular, tan spots 1 to 3 mm in diameter that may enlarge to 5 to 20 mm in size. Semicircular lesions frequently develop along the leaf margins and tips. The centers of mature lesions become black with fungal sporulation. The fungi isolated from the margins of sporulating and non-sporulating lesions were identified as three species in the Alternaria alternata complex: A. alternata, A. arborescens, and A. tenuissima (2,3). Cultures grown in the dark on potato dextrose (PDA) or potato-carrot agar are grayish white to olivacious green in the former two species and dark gray and wooly in the latter species. On 5% PDA, cultures of all three species produced catenulate dictyospores that were granular to punctate (-verrucose), pale yellowish to brown or black, and had visible apical and basal pores. Conidial morphology depended on chain position; apical conidia ranged from ovoid to ellipsoid, whereas basal conidia were elliptical to obclavate. Average conidial dimensions of A. alternata and A. arborescens ranged from 20 to 28 × 8 to 10 μm. Conidia of A. alternata were produced in acropetal succession in branching chains on single, short suberect conidiophores. A. arborescens produced conidia similarly but mostly in dichotomously branching chains on short to long conidiophores. Average conidial dimensions of A. tenuissima ranged from 20 to 34 × 8 to 12 μm and they were produced in simple chains with one or two branches forming occasionally. In preliminary studies, the optimum temperature for mycelial growth on PDA for all three species ranged from 24 to 28°C. Fifty mature leaves on each of four 7- or 8-year-old almond cv. Butte trees were inoculated at 2- to 3-week intervals from mid-spring through summer in 1999 and 2000. Leaves were sprayed with aqueous suspensions containing 105 conidia per milliliter for one isolate each of A. alternata and A. arborescens and two isolates of A. tenuissima or with sterile distilled water. The shoots were covered for 72 h with plastic-lined brown paper bags containing wet paper towels. Leaves were examined for infection after 7 and 14 days. All isolates were pathogenic and produced non-sporulating lesions similar to those observed in natural infections. No symptoms were observed on noninoculated control plants. Disease incidence was low (<15%) until late June 1999 and July 2000. Inoculations in summer produced increasingly more infections, reaching incidences of 40 to 52% in September 1999 and 18 to 80% in August 2000.

A scanning electron microscopic study of basal lamina pores on human colonic mucosas

Basal lamina pores of the human colonic mucosa were observed from the epithelial and stromal sides by scanning electron microscopy after the removal of the epithelium with boric acid and of the stroma mechanically. Their diameters ranged from 2 to 7 μm. When viewed from the epithelial side, the pores presented vacant stomata with underlying fibroblast processes, migrating cells, openings or fractured cells. When viewed from the stromal side, the pores presented vacant stomata with underlying flat epithelial cell bases or openings, or stomata containing extensions of epithelial foot processes. These findings suggest the following possible mechanisms of basal lamina pore formation: the extension of epithelial foot processes through the basal lamina; close contact between the basal lamina and fibroblast processes; and/or the passage of migrating cells.

Dome epithelium and follicle‐associated basal lamina pores in the avian bursa of fabricius

The immunological role played by the avian bursa of Fabricius has been well established. Although numerous studies have also reported on the development and general morphology of this organ, some structure-function relationships still have not been fully explained. Bursae from chickens at three developmental stages were removed and examined by scanning electron microscopy. Routine preparation was used as well as sonication (microdissection). Micrographs were used for qualitative morphological study and for quantitative morphometric analyses. Routine SEM observations were similar to those previously reported in the literature. Sonicated specimens allowed topographical study of various levels of surface erosion. Two types of surface cells were observed: typical absorptive epithelium and follicle-associated epithelial (FAE) cells. Erosion of the dome surface epithelium revealed basal lamina pores in the region over the subepithelial lymphoid follicles. These pores were present at hatching. Morphometric analysis of dome and pore areas revealed that the pore area decreases in relation to dome area with aging. Basal lamina pores may provide a communication route between the lymphoid follicles and the external environment via the FAE cells. Also, the close association between the FAE cells of the epithelial domes, the epithelial pores, the capillary complex of the previously described bursal--blood barrier, and the subepithelial lymphoid follicles could represent a morphological "pore complex" that matures early in posthatching development and may be related to the immunological function of the bursa.

Ultrastructural observations on Helvellaceae (Pezizales, Ascomycetes). V. Septal structures in Gyromitra

Ultrastructure of septa in asci, ascogenous hyphae, paraphyses, and excipular cells in selected species of Gyromitra is described. Electron-opaque, conical structures are found in the basal pores of young asci and with age bear V-shaped striations. In certain species, the pore plug is overgrown by secondary wall material. Pores of the ascogenous hyphae have a matrix of electron-dense material with a very dense zone of material around the border of the pore. Septal pores of paraphyses and excipular cells have extremely elongate, rectangular Woronin bodies in the surrounding cytoplasm. Internal striations within these bodies suggest a proteinaceous nature. Pores of the paraphyses and excipular cells may also become occluded with a matrix of electron-dense material often with striations referred to as laminate structures. Septal structures in the species of Gyromitra investigated are compared to those of Helvella and members of other families of Pezizales. Phylogenetic implications of these data are discussed.

Ultrastructural Observations on Helvellaceae (Pezizales; Ascomycetes). III. Septal Structures inHelvella

Ultrastructure of septa, asci, ascogenous hyphae, and excipular cells of apothecia of selected species of Helvella is described. Electron-opaque, hemispherical structures appear in the basal pores of young asci and with age become more pronounced within the ascus cytoplasm, eventually assuming a dumbbell-shaped appearance. Characteristic electron-opaque and -translucent, V-shaped bands develop within the plug on the ascus side of the pore. An electron-translucent torus separates the pore plug from the septal pore border. Similar pore structures are also found in ascogenous hyphae. Septal pores of paraphyses and excipular cells possess an electron-opaque, lamellate structure characteristic of other taxa of Pezizales. Unlike pores of asci and ascogenous hyphae, those of paraphyses and excipulum also have typical spherical Woronin bodies. Septal pore structures of asci and ascogenous hyphae are unlike those of the Pezizaceae and Ascobolaceae and, although distinct, are more like those ofthe Aleurieae and Otidieae ofthe humariaceous fungi, especially those of Geopyxis. Phylogenetic aspects of these data are discussed.

The nuclei of Alternaria brassicicola

Giemsa-stained preparations of Alternaria brassicicola (Schw.) Wiltsh. showed that the number of nuclei in the cells of the vegetative hyphae varied from one to many, with the hyphal tip cells having up to 27 nuclei and older cells up to 33. There were fewer nuclei (0–3) in the cells of mature conidiophores, and one or two nuclei in most cells of the conidia in three-day-old cultures grown on potato carrot agar. Nuclei were also seen wedged in the connexions between attached conidia and in the basal and apical pores of conidia after separation. They were less frequently wedged in septal pores in the conidia. These observations are discussed in relation to conidial morphology and abstriction and also to the variation in culture of Alternaria spp. Six chromosomes were counted in dividing nuclei in the vegetative hyphae, and the absence of aneuploidy is considered in relation to fitness in a rapidly reproducing fungus such as A. brassicicola .

Fine structure of the dorsal organ of the house fly larva, Musca domestica L.

The dorsal organs of the cephalic lobes of the house fly larva, Musca domestica L. were studied by light, scanning and transmission electron microscopy. Five types of receptors were found in the distal part of the dorsal organ: (1) The dome, whose ultrastructure is similar to that of thin-walled pegs, is assumed to be an olfactory receptor. (2) A lateral pore receptor, with the distal tips of two dendrites exposed to the exterior through a pore, is presumed to be a contact chemoreceptor. (3) A scolopidium-like receptor, with an ultrastructure characteristic of a scolopidium receptor except that the dendrite might be exposed to the exterior through an opening, is assumed to be both a mechanoreceptor and contact chemoreceptor. (4) Two receptors, each with one of its two dendrites exposed to the exterior, are probably contact chemoreceptors. (5) Two unclassified receptors, each with one dendritic tip exposed to the exterior and the other dendrite with a tubular body ending near the pore, may serve as both contact chemoreceptors and mechanoreceptors. The last four types are located in the invagination between the dome and the cylindrical portion of the dorsal organ. The seven basal pores of the dome are apparently points of origin of the scolopales and have no sensory function. The dorsal organ is supplied by 35–41 bipolar neurons, indicating the possibility of additional undescribed receptors.