Midrib Area Research Articles

Experimental Evaluation of Effect of Leaves on Railroad Tracks in Loss of Braking

This study aims to comprehensively assess the lubrication effect of leaves on wheel–rail contact dynamics using the Virginia Tech-Federal Railroad Administration (VT-FRA) Roller Rig, which closely simulates field conditions with precision and repeatability. Railway operators grapple with the seasonally recurring challenge of leaf contamination, which can cause partial loss of braking and lead to undesired events such as station overruns. Better understanding the adhesion-reducing impact of leaf contamination significantly improves railway engineering practices to counter their effects on train braking and traction. This experimental study evaluates the reduction in traction and braking forces (collectively called “adhesion”) as a function of leaf volume, using two leaf species that commonly grow along U.S. railroad tracks. The test methods rely on the chosen leaves’ transpiration characteristics while ensuring the result’s reproducibility. Leaves were symmetrically positioned on the wheel surface, centered around the mid-rib area within the wear band, and taped on the edges far from the wear band. The critical test parameters (i.e., wheel load, wheel velocity, and percentage creepage) are kept constant among the tests. At the same time, leaf volume is reduced from a maximum amount that covers the entire wheel surface (100% coverage) to no leaves (0%). The latter is used as the baseline. The percentage creepage is kept constant at an exaggerated amount of 2% to accelerate the test time. The results indicate a nonlinear relationship between leaf volume and the loss of braking. Even a small amount of leaf contamination causes a significant reduction in adhesion by as much as 50% compared with no contamination (i.e., baseline). Increasing leaf volume results in contact saturation, beyond which adhesion is not reduced. The minimum adhesion observed in this study is 20% of the maximum adhesion that occurs when no leaf contamination is present.

Using morpho-anatomical characters of leaves and stems for distinguishing Bolboschoenus taxa: a case study of Serbian species

The genus Bolboschoenus has been intensively studied from the morphological, ecological and physiological aspects, however, anatomical features of stems, leaves and epidermal structures of leaves have not been investigated sufficiently yet. The main objective of this study was to compare the four Bolboschoenus species growing in Serbia at the anatomical level and to define the most important anatomical characteristics for distinguishing these species. Descriptive, nonmetric multidimensional scaling and canonical discriminant analysis of the anatomical characters of leaves, stems and epidermal structures have been conducted for these purposes. The number and position of sclerenchyma strands in the leaves, the presence of bulliform cells in the epidermis, the number of translucent cell layers under the adaxial epidermis in the midrib area of the lamina, the number of aerial cavities in leaves and stems were the most significant anatomical characters for differentiation of species. The most differentiated species was B. glaucus, while B. laticarpus occupied an intermediate position between B. maritimus and B. planiculmis, on the one hand, and B. glaucus on the other. The combination of the anatomical features of leaves and stems and the epidermal structures had a more excellent taxonomic value than these three individual groups of features individually.

Leaf secretory structures in Ceiba (Malvaceae - Bombacoideae): ontogeny, anatomy and histochemistry

Abstract The description of secretory structures in Malvaceae is controversial, and results in conflicting interpretations. Amid conflicting interpretations, therefore, the present study aims to describe the ontogeny diversity and histochemistry in Ceiba, emphasizing the secretory structures in leaves of C. erianthos, C. jasminodora, C. pentandra, and C. speciosa. All analyzed species present mucilaginous, crystalliferous, and phenolic idioblasts. These structures are randomly arranged in the mesophyll, epidermis, petiole cortex, and parenchymatic tissue of the midrib. However, in C. jasminodora and C. pentandra, secretory structures are only found in the midrib area. The development of mucilaginous idioblasts is asynchronous and, when mature, they coalesce forming large structures full of mucilage. Clavate-type pluricellular glandular trichomes were also detected scattered randomly on both leaf surfaces. Their ontogeny is described, and histochemical tests showed the presence of lipophilic substances. Extrafloral nectaries were observed in the middle third of the midrib, on the abaxial side of the leaflets. They originate from the protoderm and ground meristem of the midrib cortex. It is expected that these results will help consolidate knowledge of secretory structures in Malvaceae, leading, in turn, to the elucidation of phylogenetic relationships.

Foliar application of silicon for alleviating cadmium stress and enhancing leaf anatomy in broccoli (Brassica oleracea var. Italica)

Broccoli (Brassica oleracea var. italica) is a highly nutritious vegetable known for its rich content of vitamins, minerals, and antioxidants. However, its growth is severely affected by environmental stresses, such as heat stress, drought stress, salt stress and heavy metal contamination. Cadmium (Cd) is one of the most detrimental elements. Cadmium toxicity leads to significant anatomical and physiological changes in plants, negatively impacting their growth, development, and productivity. This study explored the role of silicon (Si), a beneficial element, in mitigating cadmium stress in broccoli. Silicon has been reported to enhance plant resilience to various stresses, including heavy metal toxicity. The experiment was conducted at the Botanical Garden, Government Sadiq College Women University, where broccoli plants were exposed to varying concentrations of cadmium (0 mM, 0.5 mM, and 1 mM) and silicon (0 mM, 1 mM, and 2 mM) using a completely randomized design. Cadmium was applied to the soil during the seedling stage, while silicon was foliar applied after 15 days of cadmium stress. Results showed Cadmium reduced midrib, protoxylem, and metaxylem cell areas, with reductions of 13.6% and 33.3% in midrib area under 0.5 mM and 1 mM Cd, respectively. Silicon application improved these areas, with increases of 98.5% at 1 mM Si and 139.4% at 2 mM Si for the midrib area. Protoxylem and metaxylem cell areas were also enhanced, with increases of 69.8% and 169.8% at 1 mM and 2 mM Si. Silicon’s potential to alleviate cadmium-induced damage, enhancing vascular tissue integrity and overall plant health. Silicon application can improve broccoli growth in contaminated soils, promoting agricultural sustainability and ensuring food security in cadmium-affected areas.

Foliar application of sodium silicate mitigates drought stressed leaf structure in corn (Zea mays L.)

• Under drought stress, exogenous application of Si positively affected midrib area. • Si increased leaf stomatal area in drought stressed seedlings compared to control. • Drought stress decreased chlorophyll a and b content in 0 and 1.0 mM Si treatments. • Under drought stress Si significantly increased relative water content. • Under drought stress, K + content significantly increased when treated with si. A hydroponic study of maize cv. SC 705 was performed to determine the effectiveness of 1.0 mM sodium silicate to alleviate drought stress. Measurements were taken between 5 and 100 mm above the base of the third leaf. Stress negatively affected all growth parameters. As a general trend, a 1.0 mM Na 2 SiO 3 foliar application increased growth parameters for stressed, but not un-stressed plants, compared to the control. Leaf cross sectional area increased 35%, and midrib area decreased 25% less than in untreated stressed plants, compared to the control. Protoxylem area in treated, drought-stressed plants increased by 40%, and Si application increased xylem in non-stressed plants compared to the control. In drought stressed seedlings the stomatal area increased 24% when Si treated compared to the control. In drought stressed plants, electrolytic leakage decreased from 0.64 to 0.52% when Si treated. Membrane stability increased 12% in drought stressed plants when Si treated. When drought stressed plants were Si treated, chlorophyll a increased by 35%, chlorophyll b increased by 31%, and carotenoids increased by 51% compared to the control. Drought stressed plants had a relative water content 15% higher than non-treated plants, and leaf elongation rate increased 33%, compared to the control. Compared to the control, drought stressed plants had a 20% higher K + and 38% higher Ca 2+ level when treated with Si. These data strongly support the hypothesis that foliar Si application could mitigate the effects of drought stress. Growth improvements could be correlated with increased K + and Ca 2+ accumulation, which may play an important role in increased midrib cross-sectional area, RWC, and third-leaf elongation under drought stress. Foliar application of Si could be a low cost, easy, and effective way to improve seedling establishment in corn affected by drought early in the season.

Anatomical investigations of the Turkish critically endangered species: Achillea sivasica Çelik et Akpulat (Asteraceae)

In this study, the root, stem, leaf midrib and leaf lamina anatomy and achene micromorphology of the Turkish critically endangered endemic Achillea sivasica were investigated for the first time. In this study, the root was found in late primary growth and in early secondary growth stage. It has a large cortex layer consisting of 12-16 cell rows beneath the periderm. Secretory ducts formed by 5-12 secretory cells embedded in the cortex and located near the vascular bundle were found at the root, which was in the early stage of secondary development. The stem was circular-pentagonal in cross-section. There was lamellar collenchyma beneath epidermis of pentagon corners, and cortex parenchyma between corners. Secretory ducts located near the phloem, between the cortex and endodermis on the interfascicular region, were also observed. An endodermis layer was evident and its cells have indentations and protrusions where they touch adjacent endodermis cells, which strengthens the connection between them. In addition, casparian strips were conspicuous in many endodermis cells. The leaf midrib area had a triangular cross section. There were secretory ducts, consisting of 4-5 secretory cells observed on both sides of the sclerenchymatous fibers that accompany the xylem. The leaf lamina was amphistomatic and stomata type was anomocytic. Mesophyll layer was equifacial. There was a large secretory duct and its diameter is bigger than the nearest main lamina vascular bundle. Achene shape of A. sivasica was lanceolate-oblong and its surface was ribbed and glabrous.

Preliminary application of tapered glass capillary microbeam in MeV-PIXE mapping of longan leaf for elemental concentration distribution analysis

This study was aimed at understanding elemental concentration distribution in local longan leaf for how the plant was affected by the environment or agricultural operation. The analysis applied the MeV-microbeam particle induced X-ray emission (PIXE) mapping technique using a home-developed tapered glass capillary microbeam system at Chiang Mai University. The microbeam was 2-MeV proton beam in 130 µm in diameter. The studying interest was in the difference in the elemental concentrations distributed between the leaf midrib and lamina areas. The micro proton beam analyzed the leaf sample across the leaf midrib edge to the leaf lamina area for total 9 data requisition spots. The resulting data were colored to form a 1D-map of the elemental concentration distribution. Seven dominant elements, Al, S, Cl, K, Ca, Sc and Fe, were identified, the first six of which were found having higher concentrations in the midrib area than in the lamina area, while the Fe concentration was in an opposite trend to that of the others.

Microscopic Evaluation of Leaves ofMemecylon umbellatumBurm

Objective. Aim of present work is to perform the microscopic evaluation and physicochemical analysis and to explore the morphology parameters ofMemecylon umbellatumBurm leaves.Methods. Fresh, dried and desiccated powdered leaf samples were studied for their morphology, microscopy, organoleptic characters, and an assortment of other WHO recommended methods for standardisation.Results. The microscopy revealed the dorsiventral nature of the leaf. Midrib showed presence of nonlignified phloem, lignified xylem with well-defined xylem fibers, vessels, and parenchyma. Presence of Phloecentric vascular bundles surrounded by endodermis and crystal sheath. Well-defined patches of collenchyma were observed above and below the vascular bundles in the midrib area. Trichomes are mostly absent and stomata (anomocytic) were observed on both epidermal surfaces.Conclusions. It can be concluded that the microscopic analysis and pharmacognostic parameters can serve as tool for developing standards for proper authentication, quality, and purity ofMemecylon umbellatumBurm leaves.

Authentication of Euclea natalensis leaf by botanical identification

Microscopical characters are well established criteria in the identification and authentication of herbal drugs. Leaves of Euclea natalensis A. DC. (Ebenaceae) are commonly used in the treatment of headache and toothache, as well as for abdominal complaints and as purgative [1]. The purpose of this study was to determine the most relevant diagnostic characters to identify leaves of E. natalensis by light microscopy (LM) and scanning electronic microscopy (SEM). Used methodology includes the microscopic analysis of the whole, fragmentised and powdered dried leaves (minimum of 30 adult leaves). Results showed that among the most useful micro characters for leaf identification are the following: a thick cuticle on both epidermises; the dorsiventral organization of the mesophyll, with one to two cell layers of palisade parenchyma on the upper epidermis and spongy parenchyma with rounded cells on the lower epidermis; the midrib vascular bundle surrounded by a sclerenchymatous tissue; the xylem with numerous small vessels, radially arranged; the presence of calcium oxalate prism crystals; numerous paracytic and diacytic stomata frequent in lower epidermis with an irregular distribution and conical unicellular non-glandular trichomes, with thick walls, sometimes curved near the base and are also fairly abundant (Image 1). A developed collenchyma is present under the lower epidermis of the midrib area and near the upper epidermis. The powdered material is characterized by the presence of fragments containing the above named structures. Obtained results can be useful on quality control protocols involving this medicinal plant.

In vitro mass propagation and greenhouse establishment of Munronia pinnata (Wall) Theob. (Binkohomba)

Munronia pinnata (Wall). Theob is a valuable medicinal plant which is widely used in Ayurvedic medicine in Sri Lanka. Due to over exploitation and low percentage of seed germination of M. pinnata it has become necessary to adopt ex situ conservation methods via in vitro propagation techniques. The objectives of this study was mass propagation, greenhouse establishment and comparison of in vitro propagated plants with seed raised plants. Callus cultures were initiated from different explant types such as apical buds, nodal segments, petioles, petals and leaf discs in Murashige and Skoog (MS) medium supplemented with 1.1 mg L 1 2,4- dichlorophenoxy acetic acid (2,4-D) and 0.5 mg L 1 benzyl amino purine (BAP) at 25 ± 1°C in complete darkness. Leaf discs (6.0 mm) showed significantly higher calli production (mean fresh weight 0.167} 0.04 g) than other tested explants. The best growth regulator combination for callus initiation was 1.1 mg L12,4-D and 0.3 mg L1 BAP which produced a mean of 0.30 ± 0.06 g callus while other treatments produced lesser amount of callus. Leaf discs taken from first fully opened leafs, produced the highest amount of callus (0.06 ± 0.01 g) and a decreasing trend was observed with increased maturity of the leaf. Tissues along the midrib area have a higher potential to give high yield of callus. Shoot proliferation was higher (32.9 /* Style Definitions */ ± 2.2) in MS medium containing 3.0 mg L 1 naphthalene acetic acid (NAA) and 3.0 mg L 1 BAP. Light intensity at 3000 lx showed significantly higher number of shoots (33.4 /* Style Definitions */ ± 2.84) than other tested light intensities. Half MS minerals supplemented with 0.2 mg L1 indole acetic acid (IAA) was the most effective treatment for root induction (75%) with the highest mean root length (15.05 /* Style Definitions */ ± 0.5 mm) and 3.15 ± 0.03 of mean number of roots. A suitable potting mixture for acclimatizationwas determined using different ratios of compost and sand. Higher percentage of survival (60%) was achieved with compost: sand 1:3. When morphological features of seed raised plants were - compared with tissue cultured plants, mean height increment was higher in seed raised plants while mean number of leaves was higher in tissue cultured plants and branching habit was observed only in tissue cultured plants. A comparison of physiological parameters between the two types of plants showed that the rate of photosynthesis was higher in tissue cultured plants whereas stomatal resistance was higher in seed raised plants. Keywords: Cold treatment, commodity treatments, de-topping, hormonal regulation, shoot morphology. Normal 0 false false false MicrosoftInternetExplorer4 J. Natn.Sci.Foundation Sri Lanka 200735(3): 181-189 doi:10.4038/jnsfsr.v35i3.2017

Morphology of Dictyopteris punctata (Dictyotales, Phaeophyceae)

SUMMARY Taxonomic re-examination of Dictyopteris punctata Noda revealed vegetative and reproductive characters that were not described in the original description. The outer one-fifth to two-fifths of the blade margin was monostromatic. Reproductive organs of female and male gametophytes were observed for the first time. All reproductive organs (sporangia, oogonia, antheridia) were formed on middle to upper parts of thalli and between the midrib and distromatic area of the blades, and never produced on the monostromatic areas. Maturation starts earlier at the lower part. Sporangia were solitary and scattered. Oogonia were scattered singly or in small groups and more densely distributed than sporangia. Antheridial sori were scattered around a midrib, and raised above the wing surfaces. Antheridia were taller around the midrib than in the middle part of a wing. The monostromatic wings and lack of distinct oogonial sori are new taxonomic characters of Dictyopteris punctata and further define this species with scattered sporangia, the taxonomic character hitherto used.

Optimizing shoot regeneration and transient expression factors for Agrobacterium tumefaciens transformation of sour cherry ( Prunus cerasus L.) cultivar Montmorency

An efficient, adventitious shoot regeneration protocol was devised, and transient expression studies were carried out to enable Agrobacterium-mediated stable transformation of sour cherry (Prunus cerasus L.) cultivar Montmorency. Leaves, from in vitro stock cultures, with the petiole removed and four partial cuts made transversely and equidistant through the midrib area were found to be the optimum explant type. A 24 h liquid TDZ-pretreatment (0.05, 0.10 or 0.25 mg/l) in MS medium [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassays with tobacco tissue cultures. Plant Physiol. 15, 473–497.] of leaf explants stimulated shoot formation upon subsequent culture on QL medium [Quoirin, M., Lepoivre, P., 1977. Improved media for in vitro culture of Prunus sp. Acta Hort. 78, 437–442.] supplemented with 3.0 mg/l BAP and 0.5 mg/l NAA. A frequency of 38.9–54.4% of the explants produced at least one shoot with the maximum mean number of shoots, 4.5 per explant with the 0.10 mg/l TDZ pretreatment. The shoot regeneration scheme was subsequently linked with inoculation with Agrobacterium tumefaciens strains EHA105, GV3101 or LBA4404, each harboring the binary plasmid pBISN1. PBISN1 contains an intron interrupted ß-glucuronidase (GUS) gene (gusA) under control of the chimeric super promoter (Aocs)3AmasPmas. Blue stained leaf cells were observed after co-cultivation with all three strains. Co-cultivation for 4 days with 19.6 mg/l acetosyringone (AS) and assay by GUS indicated over 90% of the leaf explants were infected with an average 7.5–8.8 blue foci per explant. No differences were observed in regard to A. tumefaciens strain used.

Morphology and morphogenesis of ensiform leaves, syndesmy of shoots and an understanding of the thalloid plant body in species of Apinagia, Mourera and Marathrum (Podostemaceae)

The flattened, irregularly shaped and lobed or dissected leaves of Apinagia riedelii, A. latifolia, A. goejei, Mourera aspera and Marathrum utile (subfamily Podostemoideae) are ensiform in structure. After the typical bifacial inception, further growth of leaves proceeds in the midrib area, i.e. in the median plane of the leaf. The lower leaf zone is characterized by a sheath that orientates ‘at the side of the blade’, i.e. at the adaxial edge of the sword-like leaf. The ensiform blades are lobed, incised or pinnately dissected with the tips terminated in elongated threads or thin filaments. Leaves of Apinagia riedelii resemble pinnately dissected compound leaves. The dissected structure represents a secondary superimposition of the ensiform shape and a parallel development to compound leaves. It is interpreted as an adaptation to the rapid current, established in the floating shoots of these aquatic plants. The basal portions of main shoots and successive branches are fused due to a retarded separation. Fusion of this kind has been termed a syndesmy. The fused region of shoots is superseded by the fusion of the lower leaf zones of (distichously positioned) adjacent leaves, occurring at their margins. The fused leaf bases form a cavity for the terminal flower bud of each shoot and cover it in the form of a hood. The flower buds are hidden from external view. The meristematic growing zones are thus protected and enclosed within the syndesmic plant body which, in this way, attains the ‘thalloid’ appearance especially developed in Apinagia goejei and A. latifolia but also present in the other species. The results of this study enable an understanding of the particular appearance of these Podostemoideae as modifications of the typical structures according to the ‘principle of variable proportions’.

Leaf anatomical variation in Alchornea triplinervia (Spreng) Müll. Arg. (Euphorbiaceae) under distinct light and soil water regimes

Alchornea triplinervia (Spreng.) Müll. Arg. (Euphorbiaceae) is a tree which occurs in a broad range of habitats in Brazil. In the State of Rio de Janeiro, it occurs from montane forests to swamplands at sea level. A quantitative approach was used to examine the role of light and soil water regime on the variations found in anatomical traits of the palisade and spongy parenchyma, outer epidermal cell wall of the abaxial and adaxial surfaces, the percentage of sclerenchymatous area in relation to the total midrib area and the ratio of palisade to spongy parenchyma for five distinct ecological populations: M—late secondary montane forest (shaded, unflooded); M2—early secondary montane forest (semi-exposed, unflooded); SI—primary swamp forest (semi-exposed, flooded); S2—secondary swamp forest (exposed, flooded); and D—deforestation area (exposed, unflooded). Tukey tests were carried out for multiple comparisons, while one-way factor variance analysis was used to test for differences among ecological populations. A principal component analysis was used to order the populations as well as to find the higher variance component. These populations developed different response levels to the environmental factors studied, namely light and soil water regime. Light accounted for the variations found in palisade and spongy parenchyma while the combination of light and soil water determined the variations found regarding the outer epidermal cell wall of the abaxial surface, the percentage of sclerenchymatous area in relation to the total midrib area and the compaction of the spongy parenchyma. The separation of S1/M2 and S2/D populations into two groups was due to similar light regimes, which suggested that light was affecting the leaf anatomical variation of A. triplinervia more than the interaction of light and soil water regime.

Leaf anatomical variation in Alchornea triplinervia (Spreng) Müll. Arg. (Euphorbiaceae) under distinct light and soil water regimes

Alchornea triplinervia (Spreng.) Müll. Arg. (Euphorbiaceae) is a tree which occurs in a broad range of habitats in Brazil. In the State of Rio de Janeiro, it occurs from montane forests to swamplands at sea level. A quantitative approach was used to examine the role of light and soil water regime on the variations found in anatomical traits of the palisade and spongy parenchyma, outer epidermal cell wall of the abaxial and adaxial surfaces, the percentage of sclerenchymatous area in relation to the total midrib area and the ratio of palisade to spongy parenchyma for five distinct ecological populations: M1 – late secondary montane forest (shaded, unflooded); M2 – early secondary montane forest (semi-exposed, unflooded); S1 – primary swamp forest (semi-exposed, flooded); S2 – secondary swamp forest (exposed, flooded); and D – deforestation area (exposed, unflooded). Tukey tests were carried out for multiple comparisons, while one-way factor variance analysis was used to test for differences among ecological populations. A principal component analysis was used to order the populations as well as to find the higher variance component. These populations developed different response levels to the environmental factors studied, namely light and soil water regime. Light accounted for the variations found in palisade and spongy parenchyma while the combination of light and soil water determined the variations found regarding the outer epidermal cell wall of the abaxial surface, the percentage of sclerenchymatous area in relation to the total midrib area and the compaction of the spongy parenchyma. The separation of S1/M2 and S2/D populations into two groups was due to similar light regimes, which suggested that light was affecting the leaf anatomical variation of A. triplinervia more than the interaction of light and soil water regime.

A New Species of Parathesis (Myrsinaceae) from Ecuador

Parathesis palaciosii is described and illustrated, and its phylogenetic relationships are discussed. The genus Parathesis J. D. Hooker contains 130 species distributed southward from southern Mexico to Panama, the Caribbean, and through the Andes from Venezuela to Peru. The genus is defined by unique glandular papillae, which are found on the calyx and corolla lobes, and bright yellow anthers. During determination of specimens from the PROMOBOT (Promocion Botanica) project in Ecuador, a new species was encountered, which is here described. Parathesis palaciosii Pipoly, sp. nov. TYPE: Ecuador. Napo: Cant6n Tena, Estacion Biologica Jatun Sacha, Rio Napo, 8 km E of Misahualli, 1?04'S, 77?36'W, 400 m, 12-14 Dec. 1989 (fl), Palacios 4761 (holotype, QCNE; isotypes, F, MO, NY, TEX, US). Figure 1. Propter laminas chartaceas ad apices acuminatas ad bases acutas decurrentes, secus margines crenulatas, petiolo marginato, sepala ovato-triangulares, petala linearilanceolata atro-lineato-punctataque, anthera primo erecta tarde versatilis P. pyramidalis valde arcte affinis, sed ab ea laminis ellipticis vel oblongis (non oblanceolatis vel obovatis), nerviis secundariis conspicuis (non inconspicuis) desuper immersis (nec planis), sepalis 1.5-1.8 (non 11.2) mm longis, pellucido-(nec atro-)punctatis, squamis lepidotis translucentibus indutis (nec elepidotis), petalis 79 (non 5-7) mm longis, staminibus 7-8.1 (non 3-4) mm longis, filamentis 6.4-6.7 (non 2.3-2.5) mm longis, antheris apiculatis (nec obtusis) statim distinguitur. Tree to 20 m tall, 35 cm DBH; trunk prominently fenestrate, sap copious, clear, odorless; branchlets subterete, 3.5-5 mm diam., finely appressed ferrugineous stellate-tomentose. Leaf blades chartaceous, elliptic to oblong, (8-)14-17(-19) cm long, (3.7-)5-7(-7.5) cm wide, apex abruptly acuminate to caudate, base acute, decurrent on the petiole, midrib raised above and below, secondary veins (19-) 20-35 pairs, immersed above, prominently raised below, glabrous above except along midrib, sparsely and minutely ferrugineous stellate-tomentose below, bizonal, the trichomes more densely packed along the midrib area and the veins, densely and prominently punctate, the margin slightly revolute, crenNOVON 3: 176-178. 1993. ulate; petioles marginate, (1.8-)2.5-3 cm long, glabrous above, densely and minutely ferrugineous stellate-tomentose below. Inflorescence bisexual, terminal, pyramidal, bipinnately paniculate, (6-)1216 cm long, (6-)10-12 cm wide at base, the principal branches subtended by small leaves, the leaf blades chartaceous, elliptic, 4.5-7.5 cm long, 1.73.5 cm wide, apex acuminate, base acute, decurrent on the petiole, otherwise as in vegetative leaves; petioles marginate, 0.7-1 cm long, glabrous above, sparsely and minutely ferrugineous stellate-tomentose below; peduncle obsolete to 1.5 cm long, rachis, branches and pedicels densely appressed ferrugineous stellate-tomentose; floral bracts chartaceous, linear-lanceolate, 2.5-3 mm long, ca. 0.1-0.2 mm wide, apex subulate, early caducous; pedicels cylindrical, erect, 4.8-7.2 mm long, not accrescent in fruit. Flowers corymbose, 5-merous, 7-9.2 mm long, calyx brown, chartaceous, inconspicuously pellucid punctate, densely and minutely tomentose, the sepals ovate-triangular, 1.5-1.8 mm long, 0.9-1.3 mm wide, apex acute, sparsely translucent-lepidote, the margins entire; petals pink, chartaceous, linearlanceolate, 7-9 mm long, 1.5-1.9 mm wide, apex subulate, densely and prominently black punctatelineate (the punctations linear), densely and minutely stellate-tomentose without, densely translucent papillose-tomentose along the margin within and throughout the distal 1/3; stamens 7-8.1 mm long, erect, the filaments flat, 6.4-6.7 mm long, prominently black punctate-lineate, the anthers erect, then tardily versatile, lanceolate, 2.2-2.5 mm long, 11.2 mm wide, apex apiculate, glabrous, base sagittate, dehiscent by longitudinal slits; ovary globose, densely tomentose with erect hairs, the style filiform, accrescent to 11.7 mm long, the placenta depressedglobose with 4-5 uniseriate immersed ovules. Fruit depressed-globose, 6-8 mm long, 10-12 mm diam. at maturity, black, the exocarp thick, juicy, sweet. Distribution. Parathesis palaciosii is endemic to the Ecuadorean Amazon in the area of the Jatun Sacha Biological Reserve, 400-450 m elevation. Ecology. This species occurs in tall very humid forest on rolling hills of lateritic soils. The species is frequently encountered and is a conspicuous element of the subcanopy, according to the collector. This content downloaded from 207.46.13.124 on Wed, 22 Jun 2016 06:08:46 UTC All use subject to http://about.jstor.org/terms Pipoly Parathesis palaciosii Volume 3, Number 2 1993

The taxonomic significance of anatomical characters of the leaf in the southern African species of Canthium s.l. (Rubiaceae)

Fourteen species of Canthium s.l. recorded in southern Africa were studied. The anatomy of the leaf is described and the taxonomic and diagnostic value of the characters discussed. As with the stem, several anatomical features of the leaf are useful in distinguishing between taxa. These include the structure of the hairs, the thickness of the lamina, the shape of the midrib area, the thickness of the cuticle, the shape of the epidermal cells, the distribution of stomata, the extent and pattern of cutinization of the epidermal cells, the composition of the mesophyll including the abundance and distribution pattern of tanniniferous cells and the shape of the collenchyma in the midrib area. With regard to relationships between species not necessarily confined to southern Africa, indications are that leaf anatomical features may be of value. It also appears that leaf anatomy may be useful for diagnostic purposes irrespective of the stage of development of the leaf. On the basis of leaf anatomy three distinct groups were recognized, corresponding with the recently proposed segregate genera Canthium Lam. s.str. (in a southern African context), Psydrax Gaertn. and Keetia Phill. Nearly all species are anatomically homogeneous and all species could be distinguished from one another.

Notes on the Systematics of Hesperantha (Iridaceae) in Tropical Africa

Notes on the Systematics of Hesperantha (Iridaceae) in Tropical Africa

Density and Distribution of Erect Glandular Hairs on Annual Medicago Species

Erect glandular hairs on several annual Medicago species are associated with mechanisms that defend the plants against certain destructive insects. To aid in elucidating the resistance mechanism, we investigated the density and distribution of erect glandular hairs on four annual Medicago species: two tetraploids (2n = 4x = 32), M. scutellata (L.) Mill. and M. rugosa Desr., and two diploids (2n = 2x = 16), M. disciformis DC. and M. blancheana Boiss. Erect capitate glandular hairs were present on all vegetative and floral parts of the four species except cotyledons and flower petals. Density was not affected by ploidy level but showed differences, depending on whether the plants had been grown in the field or greenhouse. Both diploids and tetraploids had glandular hairs on margins of leaflets. The glandular hairs were distributed over the entire abaxial leaf surface of tetraploids, and on diploids they were confined to the midrib area. Hairs were densest on the peduncle, followed by the stem, petiole, seed...

Distribution of microfungi over the surfaces of attached leaves of Hippophaë rhamnoides

The distribution of microfungi over the leaf surfaces of Hippophae rhamnoides L. was investigated using a variety of observational and cultural techniques. Many of the fungi were associated with the midrib of the leaf, particularly on the upper surface where a groove overlaid the midrib vein. On the leaf lamina fungi were not associated with the network of subsidiary veins. Fungi were, however, associated with the trichomes on the lamina. Evidence of active growth in the midrib area was found for Aureobasidium pullulons, Cladosporium herbarum, Sporobolomyces spp., Phoma sp., sterile mycelium 1 and, possibly, Epicoccum purpurascens and Cephalosporium acremonium. A. pullulans, C. herbarum and some unidentified fungi were observed growing on and inside the trichomes on the leaf lamina where Phoma sp., sterile mycelium 1, E. purpurascens, C. acremonium, A. alternata, B. cinerea and Fusarium spp. were present mainly as spores or propagules.