Monopodial Branching Research Articles

Pamukta Bazı Karakterlere İlişkin Heterotik Etkiler ve Korelasyon Analizleri

This research was conducted at the Dicle University Faculty of Agriculture Experimental Area of Field Crops. The objectives of the study were to investigate the heterotic effects of earliness and agronomical and quality characters on F1 and F2 generations of cotton plant. In 2003, F1 generation, and in 2004 F2 generation were obtained, and in 2005, F1 and F2 generations were grown with parents in randomized block design with three replications. The highest heterosis was observed in the monopodial branch (-58.33%), and number of first sympodial branch (-30.85%), height of first sympodial branch (-13.87%), date of first square (- 13.87%). However, the highest F2 depression and F2 deviations were determined the same characters.

Anthropometry of fetal vasculature in the chorionic plate

Normal fetal development is dependent on adequate placental blood perfusion. The functional role of the placenta takes place mainly in the capillary system; however, ultrasound imaging of fetal blood flow is commonly performed on the umbilical artery, or on its first branches over the chorionic plate. The objective of this study was to evaluate the structural organization of the feto-placental vasculature of the chorionic plate. Casting of the placental vasculature was performed on 15 full-term placentas using a dental polymer mixed with colored ink. Observations of the cast models revealed that the branching architecture of the chorionic vessel is a combination of dichotomous and monopodial patterns, where the first two to three generations are always of a dichotomous nature. Analysis of the daughter-to-mother diameter ratios in the chorionic vessels provided a maximum in the range of 0.6-0.8 for the dichotomous branches, whereas in monopodial branches it was in the range of 0.1-0.3. Similar to previous studies, this study reveals that the vasculature architecture is mostly monopodial for the marginal cord insertion and mostly dichotomous for the central insertion. The more marginal the umbilical cord insertion is on the chorionic plate, the more monopodial branching patterns are created to compensate the dichotomous pattern deficiency to perfuse peripheral placental territories.

Comparative yield component analysis in Gossypium hirsutum parents using fibre quality grouping

The usual practice of estimating association and direct and indirect effects among various traits in Gossypium hirsutum is with ungrouped genetic material based on staple length and strength. During 2003–2004 and 2004–2005 genotypic and phenotypic association among ten characters were estimated in G. hirsutum genotypes: (i) set-1: 10 genotypes of low fibre strength (≤196.2 mN/tex) and medium staple length (≤25.0 mm), (ii) set-2: 10 genotypes of high fibre strength (≥235.44 mN/tex) and long staple length (≥28 mm) and (iii) set-3: 20 genotypes of set-1 and 2. The differences in the estimates of associations, direct and indirect effects for different characters in fibre quality groups were examined. The complete analysis of variance for the characters under study viz; days to 50% flowering, plant height (cm), number of monopodial and sympodial branches per plant, seed cotton yield per plant (g), boll weight (g), total number of bolls per plant, lint %, 2.5% span length (mm) and fibre strength (mN/tex) indicated highly significant genotypic differences for genotypes, years and genotype × years interaction. Variation within medium staple length and low strength (set-1), high staple length and high strength genotypes (set-2) and their interaction with year were also significant. Medium staple length and low strength (set-1) versus high staple length and high strength component (set-2) was significant for all the traits indicating significant variability between the sets. A true relationship and direct selection were observed for days to 50% flowering, number of monopodial and sympodial branches per plant with seed cotton yield in the three sets suggesting that separation of genetic material based on staple length and fibre strength for improvement of seed cotton yield through these traits is not required. Magnitude and direction of direct effect and association with yield of the other traits; plant height, number of total bolls per plant, boll weight, lint %, staple length and fibre strength differed between the sets. This study concluded that more successful planning of a breeding programme can be made through path coefficient analysis if the genetic material is grouped based on staple length and fibre strength.

Combining ability and heterosis for earliness characters in line×tester population of Gossypium hirsutum L.

The objective of this study was to estimate the general combining ability of the parents and specific combining ability of hybrids for earliness traits for line selection. Inheritance and interrelationships of earliness characters were evaluated in a line x tester design. Three intermediate-early-maturing female (lines) which are grown regionally and four early-maturing males (testers) cotton varieties were crossed in 2003. The twelve F(1) and seven parents were planted randomized block design with three replications in 2004. For each earliness trait, general combining ability (GCA) and specific combining ability and gene effects were estimated using the line x tester method of analysis and also were determined heterosis and narrow sense heritability. Parents and their hybrids (except the monopodial branch) were significant for all the earliness traits studied. Estimates of variance due to GCA and SCA and their ratio revealed predominantly non-additive gene effects for date of first square, date of first flowers and harvested rate of first picking. Among the lines, Ersan 92 and Maras 92 and among the testers Acala Royal was found to be the best general combiners for most of the earliness characters. Four out of twelve crosses namely Ersan 92 x Chirpan 603, Ersan 92 x Acala Maxa, Maras 92 x Acala Royal and Nazilli 87 x Acala Royal were found to be the best crosses for investigated earliness characters.

Registration of ‘NIBGE‐2’ Cotton

M. Rahman and Y. Zafar, Plant Genomics & Mol Breeding (PGMB) Labs., National Institute for Biotechnology and Genetic Engineering (NIBGE), P.O. Box 577, Jhang Road, Faisalabad, Pakistan. Registration by CSSA. Received 10 Dec. 2006. *Corresponding author (mehboob@nibge.org or mehboob_pbd@yahoo.com). NIBGE-115 cotton (Gossypium hirsutum L.) (Reg. No. GP-880, PI 643972) was developed in 2002 by the Plant Genomics and Molecular Breeding (PGMB) Labs, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan, and was released in 2006. It was bred as part of an ongoing effort to develop cultivars with improved resistance to a resistance breaking strain of cotton leaf curl disease (CLCuD; transmitted by the whitefl y Bemisia tabaci Genn.) called the Burewala strain (Briddon, 2003). The original strain of CLCuD is caused by one (or more) of seven begomoviruses and a distinct DNA satellite (Briddon et al., 2001; Briddon, 2003). The resistance breaking strain of CLCuD (Burewala strain) has yet to be fully characterized but is associated with a recombinant satellite (Amin et al., 2006). NIBGE-115 was developed by pedigree selection from a cross (made in 1997–1998) of the unreleased genotype LRA-5166 (primary source of resistance to the old strain of CLCuD) and ‘S-12’ (highly susceptible to the old strain of CLCuD). The F2 plant from the cross along with spreader rows of the highly susceptible S-12 (every third row) were sown in the last week of June 1998 at NIBGE cotton fi eld to ensure maximum infection (Rahman et al., 2002). No whitefl y control measures were implemented, thus allowing the spread of vector populations throughout the season. F2 plants and succeeding generations were screened using three procedures: fi eld evaluation, whitefl y transmission assay, and graft inoculation (Rahman et al., 2002). Viral infection of the plant was determined by visual symptom assessment as well as dot-blot and multiplex polymerase chain reaction (PCR) diagnostic techniques (Rahman et al., 2005). Greenhouse grown F3 progeny of the resistant F2 plants were raised and screened by the visual assessment and multiplex PCR diagnostic tests. Resistant F3 plants were advanced to F4 and again subjected to screening tests in 1999. The procedure was repeated to F7. These lines were given the acronym NIBGE after the institute’s name, National Institute of Biotechnology and Genetic Engineering, in 2002. In the normal cotton growing season of 2002–2003, the recombinant inbred lines resistant to the old strain of CLCuD were grown in the Burewala region (Cotton Research Station, Vehari, Pakistan) to provide maximum inoculum of the Burewala strain of CLCuD. Out of these, NIBGE-115 was found virus free (Rahman et al., 2004; Rezian, 2005). In 2003–2004, NIBGE-115 along with cultivars and genotypes highly susceptible and resistant to the old virus strain of CLCuD were raised in the Burewala region and screened for resistance to Burewala strain, both visually and with a PCR-based diagnostic test (Amin et al., 2006). A standard randomized complete block design with four replications was followed. The screening was continued for two successive normal cotton-growing seasons (2004– 2006). Out of the 20 cotton cultivars and genotypes, NIBGE-115 showed fi eld resistance against the Burewala strain of CLCuD. NIBGE-115 is nectaried, possesses normal-shaped leaves and bracts with pubescent stems and leaves, and is glanded, exhibiting a spreading type plant habit with 0 to 4 monopodial branches. Flowering initiates 40 to 47 d after planting with the pollen being cream colored. Average lint yields of the NIBGE-115 were 7.48% more than CIM-496 (standard) at all locations conducted from 2004 to 2006. Fiber properties of the line (measured with high volume instrument) were fairly acceptable (3% shorter, 5% stronger, and 5% higher micronaire value than that of CIM-496). The germplasm will be useful for breeding cultivars against the Burewala virus strain of the cotton leaf curl disease. Limited quantity of seed will be distributed on written request to the corresponding author. The receiving agency or entrepreneur will be asked to make appropriate recognition of the source of germplasm if it contributes in developing hybrids, new cultivars, or breeding lines.

Modeling lung cancer incidence in rats following exposure to radon progeny

Lung cancer incidence in Sprague-Dawley rats was simulated by a biologically based carcinogenesis model, which is formulated mathematically in terms of a stochastic state-vector model. Doses to the sensitive target cells in the bronchial epithelium of the rat lung were calculated by a stochastic dosimetry model, considering the distinct monopodial branching structure and the crossfire of alpha particles from alveolar tissue to bronchial epithelium. Bronchial and alveolar cellular doses could reasonably be approximated by lognormal distributions, with geometric standard deviations (GSD) between 7 and 10, depending on exposure conditions. Based on a dose-exposure conversion factor of 8.5 mGy WLM(-1) and a GSD of 8, lung cancer incidences were calculated for each cumulative exposure category in the rat inhalation study, consisting of different exposure rates and exposure times. The fair agreement between theoretical predictions and experimental data over the whole exposure range emphasises the necessity to incorporate the full cellular dose distributions rather than their mean values.

Effect of Cotton Leaf Mosaic Disease on Morphology, Yield and Fibre Characteristics of Upland Cotton in Pakistan

The effect of cotton leaf mosaic disease on morphology, yield and fibre characteristics was examined for a susceptible cotton candidate variety CRIS-168. Plants inoculated at most susceptible growth stage (six week) under screen house showed severe mosaic symptoms. There was a significant reduction in plant height and yield. Cotton leaf mosaic disease was found to produce severe effects on plant morphology with 24.1% reduction in plant height, 25% in internode length and 37.5% in number of sympodia on main stem. However no changes were observed against number of monopodial branches per plant. Inoculated plants showed 82% decrease in yield/plant, 80% in number of boll set/ plant, 12.1% in boll weight, 12.8% in lint weight, 10.8% in seed weight, and 6.8% in seed index. Cotton leaf mosaic disease also showed effects on fibre characteristics with 0.8% decrease in GOT and 1.6% in fibre length. In contrast, uniformity ratio, fibre fineness and maturity index was increased by 20.5%, 14.4% and 0.9%, respectively.

Cotton growth and yield after seed treatment with mepiquat chloride in the tropical winter season

Cottonseed ( Gossypium hirsutum L.) was treated with mepiquat chloride (MC) to examine its potential for the management of vigorous early growth experienced on cotton grown in the tropical winter season. As there is little published research from the field on this topic, we aimed to determine the effect of seed treatment of cotton with MC grown to maturity. In two field experiments over two seasons the seed surface was treated. Seed surface treatment was compared with pre-sowing priming with MC in experiment 2. Lint yields were high, 2059 and 2270 kg/ha averaged over all treatments in experiments 1 and 2. In both experiments, seed surface treatment with 2 g MC/kg reduced ( P < 0.05) plant height for up to 30 days after sowing and there were no significant changes to rate of crop development, time to maturity, lint yield or fibre quality. In experiment 2 treating with MC reduced plant establishment in proportion to the amount of MC applied ( P < 0.01). Pre-sowing priming caused approximately twice the reduction in plant height per gram of MC than surface treatment and significant differences persisted longer, even until maturity using 8 g MC/kg seed. Priming with ≥4 g MC/kg seed had additional effects ( P < 0.05): (1) reduced node development between first square and first flower, (2) delayed the time to first square, first flower and maturity by 4 days, (3) increased production of bolls on monopodial branches, and (4) reduced lint yield compared to the same concentrations applied to the surface. Fewer smaller plants having smaller bolls were implicated in this response. It was concluded that the relative benefit of seed treatment with MC at the concentrations and methods that did not reduce lint yield appears questionable as height reductions per gram of MC/ha were less than measured at this location with the same amount applied as a foliar spray.

Within-tree variations in shoot differentiation patterns of 10 tall tree species in a Japanese cool-temperate forest

The relations of leaf–stem balance, stem thickness, leaf thickness, and leaf size to stem length of current-year shoots were compared between terminal and lateral shoots in saplings of 10 tall tree species in a Japanese cool-temperate forest. Six monopodial and four substitution sympodial branching species were studied. For both terminal and lateral shoots, the ratios of leaf area / stem length, leaf mass / stem mass, and leaf number / stem length were greater in shorter current-year shoots, implying shoot differentiation such that short current-year shoots specialize in leaf display and long current-year shoots in crown expansion. These ratios were generally greater for terminal shoots than for lateral shoots, especially in the lower range of stem length. This tendency was more conspicuous in the ratio leaf area / stem length than in leaf mass / stem mass and leaf number / stem length, because terminal shoots showed greater stem mass / stem length, leaf area / leaf mass, and leaf area / leaf number ratios than lateral shoots. These terminal–lateral variations were generally greater in the monopodial species than in sympodial species. These observations are discussed in relation to differences in ecological functions and hydraulic architecture between terminal and lateral shoots, and in relation to apical control and branching patterns (the monopodium and the sympodium).Key words: shoot functions, apical control, short shoots, terminal shoots, monopodial branching, substitution sympodial branching.

Morphological Studies toward an Improved Classification of Campanulaceae s. str.

Growth and seedling morphology of 144 species representing 30 genera of Campanulaceae s. str. were studied. Two types of seedlings were found: Group A, with an elongated epicotyl and elongated internodes, and Group B, with a shortened (not visible) epicotyl and usually shortened internodes. These two types appear to be correlated with other vegetative characters. Thus, plants from Group A have an opposite leaf arrangement (at least early in ontogenesis), rhythmic seasonal growth with a long dormant period, and sympodial branching. Plants from Group B have a spiral leaf arrangement, continuous growth (at least in the non-flowering period), and sympodial and monopodial branching. Taxa in Group A are distributed mostly in Asia, whereas representatives in Group B occur almost worldwide. The two groups do not coincide with current taxonomic classifications but correspond remarkably well with the distribution of other characters such as pollen-grain morphology and correlate with groups based on molecular analysis; therefore, these two groups may reflect two lineages. Growth and seedling morphology are of taxonomic significance in Campanulaceae and can be used for treatments in conjunction with other characters. Taxonomic changes, which are supported by molecular data, are proposed.

Ectomycorrhizae between Alnus acuminata H.B.K. and Naucoria escharoides (Fr.:Fr.) Kummer from Argentina.

Field ectomycorrhizae of Naucoria escharoides on Alnus acuminata ("andean alder", "aliso del cerro") are described in detail for the first time. Naturally occurring ectomycorrhizal roots were sampled beneath sporocarps of N. escharoides. The samples were taken from four natural forest plots at two homogeneous A. acuminata sites (Tucumán and Catamarca Provinces, Argentina). The ectomycorrhizae were characterized morphologically and compared by means of PCR/RFLP analysis of the internal transcribed spacer region of the nuclear rDNA. The most important morphological features of the ectomycorrhizae are a white to pale yellow mantle, simple to monopodial branches, hyaline emanating hyphae, abundant hyphal bundles emerging more or less perpendicularly from a plectenchymatous mantle, and an acute or rounded apex with or without a mantle. N. escharoides fruitbodies have white basal mycelium with emanating hyphae similar to those of andean alder ectomycorrhizae. The RFLP profiles of sporocarps and mycorrhizae were the same.

Early Flower Bud Loss and Mepiquat Chloride Effects on Cotton Yield Distribution

Abscission or abortion of the initial cotton (Gossypium hirsutum L.) flower buds or bolls increases the importance of retaining fruit on adjacent or subsequent fruiting positions. Use of the plant growth regulator mepiquat chloride (MC) (N, N dimethylpiperidinium chloride) improves boll retention on lower reproductive branches (sympodia), reduces vegetative growth, and in some cases reduces upper sympodial productivity. Our objective was to determine the effect of doses and application timings of MC and different levels of early flower bud removal on within‐plant yield distribution. Zero or an average of two or four flower buds located at first positions on lower sympodia were removed from each plant prior to MC applications at two field locations in 1992. This bud loss resulted in higher retention at second positions on lower sympodia and on slightly higher sympodia. Two biweekly doses of 24.5 g ha−1 of MC applied at early bloom also enhanced compensation and yield on lower sympodial second positions. Primarily at one location, four weekly MC doses of 12.25 g ha−1 each beginning when buds were 1 cm long resulted in increased monopodial branch yield when there was moderate early bud loss. Depending on field location, one or the other of the MC treatments reduced the number of fruiting positions and yield on higher sympodia when fruit retention on lower sympodia was high. Loss of early buds, which resulted in small increases in vegetative growth, ameliorated this effect. The biological responses produced by early bud loss and MC treatments interacted positively. After early bud loss, plants treated with MC generally improved compensation on lower sympodia without negative effects on upper sympodia.

Analysis of Cotton Yield Stability Across Population Densities

Final lint yield in cotton (Gossypium hirsutum L.) is relatively stable across a wide range of population densities. This study was conducted to determine (i) which components of final lint yield impart this yield stability across plant populations and (ii) how yield distribution is influenced by population density. Studies were conducted in 1997 and 1998 on a Tifton loamy sand (Fine‐loamy, kaolinitic, thermic Plinthic Kandiudults). Cotton was planted in each study on 91‐cm row widths at seeding rates ranging from 3.5 to 25.1 seeds m−2. At harvest, each plot was hand picked and boll numbers and weights were recorded at each monopodial branch and sympodial branch fruiting position. Lower population densities led to plants with more mainstem nodes and monopodial branches with increased fruit retention, resulting in greater fruit production per plant. Boll size was inversely related to population density. Mean net assimilation rate from first flower to peak bloom also was related inversely to population density. The mainstem node of peak boll set increased with population density. Fruit production on a ground area basis was greater in the first sympodial position as population density increased, while fruit production on a ground area basis in third positions and monopodial branches was greater as population density decreased. Accumulative seedcotton from sympodial branches also increased with population density. Total fruit number and seedcotton yield per area were not influenced by population density in these studies. Yield stability across population densities was achieved through manipulation of boll occurrence and weight.

Two New Species of Acritopappus (Compositae: Eupatorieae: Ageratinae) from Bahia, Brazil

Two new species of Acritopappus, A. catolesensis D. J. N. Hind & Bautista and A. pintoi Bautista & D. J. N. Hind from the Chapada Diamantina, Bahia State, Brazil, are described and illustrated. The genus is predominantly from the campos rupestres of Bahia and Minas Gerais States, and 15 species are now recognized in Bahia. The first new species, because of its typical monopodial primary axis and decussate side branches and inflorescences, falls into a group of non-viscid leaved species. The second species, unique in the genus, is a distinctive tree, and has unusual leaf and inflorescence characters. The tree-like nature of the species in the genus is discussed relative to the terminology usually applied to many members of the Compositae found in Brazil.

Dosimetry of Particles: Critical Factors Having Risk Assessment Implications

Species differences in the handling of particles are topics of interest for setting ambient particulate matter standards as well as for studies involving the phenomenon of lung overload and the implications, if any, of such studies for workplace dust exposure standards. The dosimetry of inhaled particles differs among the three major regions of the respiratory tract (extrathoracic, tracheobronchial, and pulmonary). Particulate dosimetry includes both deposition, which is the process of removing particles from inhaled air to various locations in the respiratory tract during breathing, and clearance, which refers to the rates and routes by which deposited particles are removed from the respiratory tract. Species-specific structure of respiratory-tract regions combines with the route and depth of breathing to greatly influence where particles deposit. The dominant mechanisms for deposition and clearance of inhaled particles differ by region. Inertial impaction is important for head deposition in humans of large particles and for tracheobronchial deposition of particles larger than about 2.5 μm in aerodynamic diameter. Enhanced head deposition of ultrafine particles due to diffusion occurs in both laboratory animals and humans since nasal turbinate surfaces are large compared with the cross-sectional area and are in close proximity to the airstream. Deposition in the tracheobronchial region of rats is due to impaction and sedimentation mechanisms for particles larger than about μm in aerodynamic diameter. Factors such as inhalability, oronasal breathing, and heterogeneity in tracheobronchial path length and acinar volume affect the deposition of particles in laboratory animals and humans to differing degrees. While particles less than 5 μm in aerodynamic diameter are completely inhalable by humans, inhalability in rats decreases from 97 to 65% as aerodynamic particle size increases from 0.5 to 5 μm. Rats are obligate nasal breathers, but humans switch to oronasal breathing when work or exercise requires a minute ventilation that exceeds about 35 L/min. This species difference has significant implications for particulate risk assessments. The monopodial branching system of the tracheobronchial airways of rats compared with bipodial or tripodial branching in humans can impart significant intra- and interspecies heterogeneity in the deposition of particles in the alveolar region. Clearance mediated by alveolar macrophages (AM) is an important factor in lung overload phenomena associated with chronic studies in rodents of poorly soluble particles. Data presented on AM characteristics across species support the notion that various dose metrics need to be examined that may better reflect critical steps in the process of lung overload.

Influence of epidermal growth factor and transforming growth factor beta-1 on patterns of fetal mouse lung branching morphogenesis in organ culture.

Transforming growth factor-beta (TGF-beta), a potent inhibitor of epithelial cell proliferation, and epidermal growth factor (EGF), a mitogenic polypeptide that binds to cell surface receptors, are important regulators of cell differentiation; however, their distinct role(s) in lung development and their mechanisms of action are not well understood. We evaluated the effects of these factors on lung morphogenesis in murine fetal lungs at gestational day 14 (time:zero) and again after 7 days in culture. Baseline controls were cultured after tracheal transection in supplemented BGJb medium, and other tracheally transected lungs were cultured following addition of EGF (10 ng/ml BGJb), TGF-beta1 (2 ng/ml BFJb), or with both in combination added to the medium. The control lungs in culture had poorly developed airways and an absence of defined acinar structures. The addition of EGF resulted in hyperplasia of primary airways with stunted outgrowths, monopodial branching, and absence of distinct acinar structures. Addition of TGF-beta1 alone, led to significant elongation of primary airways, without normal airway branching; however, terminal dipodial branching was seen and the prospective pulmonary acini were well defined. Combination of these growth factors (GF) resulted in a more normal branching pattern and differentiation, suggesting their epigenetic role in lung morphogenesis and mutual interactive mechanisms that regulate lung development. These lungs had more abundant and larger lamellar bodies than those after other treatments. Control lungs remained immature with prominent glycogen aggregates with occasional dense lamellar bodies. The total protein and DNA contents were highest with EGF treatment, followed by combination treatment; these observations were supported by immunohistochemical localization of proliferating cell nuclear antigen, an indication of the proliferative state of tissues. All the surfactant proteins were relatively unaltered and their messages were up-regulated for SP-A, but down-regulated for SP-B and SP-C in the lungs treated with growth factors. In conclusion, we have demonstrated enhanced biochemical and structural development of lungs treated in vitro with GF, and propose that further research in this area may lead to therapeutic uses of GF alone or in combination with other agents for the treatment of newborn respiratory distress due to lung immaturity or hypoplastic lung development.

Form and function of mammalian lung: analysis by scientific computing.

This study approaches the investigation of airway morphology of the lung with a new set of imaging and computer graphical methods, including confocal imaging, computer-guided image acquisition, visualization and fractal graphics. The key result is that, in contrast to the belief that the design of the conductive part of lung of smaller mammals can be described with a trumpet model, the findings reported here document a strongly monopodial branching pattern with the functional consequence of a variation of dead space between the trachea and the acini. This non-dichotomic structural design finds its continuation within the respiratory units as the necessary requirement for an optimal space filling and dense packing which cannot be achieved by a dichotomic branching only. Based on a computer model, computational physics tightly coupled with computer visualistics enables functional simulation of the lung model regarding gas transport. The predicted variance in the ventilation of acini gives rise to an explanation of the well-known difference between the morphologically predicted and physiologically required diffusion capacity.

Studies on Dasyaceae. 1. Reproductive structures of Eupogodon planus and E. spinellus (Ceramiales, Rhodophyta) from Corsica (Mediterranean)

Reproductive structures of Eupogodon planus (C. Agardh) Kützing and E. spinellus (C. Agardh) Kützing, including the tetrasporangial stichidia of both species and mature carposporophytes and spermatangial branches of E. spinellus, are described for the first time. Early procarp development of E. spinellus is also described. The female reproductive system of E. spinellus closely resembles that in the genus Dasya C. Agardh, the proposed sister genus of Eupogodon Kützing. Similar features include procarp position on the central axis, number of periaxial cells and manner of their formation, location of the supporting cell, number and arrangement of sterile cells, absence of pericarp initials before fertilization, the monopodial branching of the gonimoblast, and the development of the carposporangia in terminal chains. As regards the tetrasporangial stichidia, however, the two genera differ markedly in the number of sporangia per stichidial segment, although sharing the character of postsporangial cover cells that only partially envelop the tetraspores. The taxonomic status of both Eupogodon species is discussed in light of the present findings, and the family Dasyaceae is re-evaluated on the basis of reproductive structures.

Effect of triamcinolone acetonide on the development of the pulmonary airways in the fetal rat.

Triamcinolone acetonide (TAC) has a potent teratogenic effect on various mammalian fetal tissues as well as a steroid effect on the lung. Less well documented is the fact that it produces profound oligohydramnios. We wished to determine what effect TAC would have on branching morphogenesis and other aspects of lung development, using an in vivo model described previously. Thirty rats were randomized to receive 0.6 mg/kg of TAC or saline on days 12, 13, and 14 of gestation. At gestational days 15, 17, 18, and 21, the left lungs of 365 fetuses were studied by dissecting microscopy, histology, and morphometry. TAC produced profound pulmonary hypoplasia (dry Jung weight/body weight 0.025, compared with 0.06 in controls) on day 21. TAC decreased maternal weight gain, fetal weight, placental weight, aminiotic fluid, and pole to pole length (PTP), while it increased the peripheral airway count (PAC). The number of central and intermediate airway branches was reduced, and they were dilated. Growth of peripheral airways was enhanced. In treated fetuses epithelial cells lining these airspaces were histologically more mature and the mesenchyme thinner than in controls. These findings were confirmed by the morphometric measurements. We conclude that when TAC is administered in the early phase of fetal rat lung development, the lungs become hypoplastic, with hypoplasia of the intermediate airways, an increase in the number of peripheral airways, and increased differentiation. We speculate that these effects are primarily due to the steroid action of TAC and that the mechanisms of monopodial branching are different from those of dichotomous branching.

Size-dependent morphology of the conductive bronchial tree in four species of myomorph rodents.

Size-dependent structural patterns in the conductive bronchial tree of four species of myomorph rodents of different body weight were determined by lung casts. The lungs of the harvest mouse, Micromys minutus, body weight 5-7 g, the house mouse, Mus musculus, body weight 35-45 g, the brown rat, Rattus norvegicus, body weight 200-400 g, and the African giant pouched rat, Cricetomys gambianus, body weight 1,200-1,800 g, were inflated to 20 cm H2O, frozen, freeze-dried, hardened, and filled with silicone rubber. The casts were pruned, and branching pattern, diameter, and volume of the conductive bronchial tree were determined using a binocular magnifier. All four species have four lobes on the right lung and an undivided left lung, and the central bronchial tree on either side shows an identical monopodial branching pattern. Although the ramification of the central conductive bronchi is not size-dependent, the diameter and volume are. The diameter of the left main bronchus equals 1.24% of body length in Micromys and 0.6% in Cricetomys, and the conductive bronchial tree makes up 13% of the total lung volume in Micromys and 6% in Cricetomys. Relatively wider airways and a decline in airway resistance with declining body mass in small mammals compared to large ones result in a high ventilatory dead space, which is compensated for by a higher breathing frequency.