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Wouter G Van Doorn - One of the best experts on this subject based on the ideXlab platform.
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bending in cut gerbera jamesonii flowers relates to adverse water relations and lack of stem Sclerenchyma development not to expansion of the stem central cavity or stem elongation
Postharvest Biology and Technology, 2012Co-Authors: Rene R J Perik, Dephine Raze, Harmannus Harkema, Yuan Zhong, Wouter G Van DoornAbstract:Abstract We studied stem bending in cut Gerbera flowers (Gerbera jamesonii cv. Tamara). Bending might be due to turgor loss. During vase life water uptake decreased more rapidly than transpiration, hence the flowers lost water. Net water loss did not occur in the floral head, but was found in the stem. It was largest in the segment (10–15 cm below the floral head) where bending was localised. When comparing flowers that showed stem bending with those that did not, on day 7 of vase life, the fresh weight loss of 5 cm stem segments was higher in the stems that had bent. Covering the stems with a flexible, thin sleeve of polypropylene plastic reduced transpiration and increased the time to stem bending from d 7 to d 14 of vase life. Additionally, stem bending might relate to stem elongation and to stem morphology and anatomy. Stems elongated by 1–1.5 cm, in the uppermost 10 cm, during the first two days of vase life. No relationship was found between stem elongation and bending. At harvest, the stems contained a large central cavity, starting at about 5 cm from the root–shoot junction, and ending about 10 cm below the floral head. The cavity extended upwards and laterally during vase life, but no relationship was found between cavity formation and stem bending. A cylinder of Sclerenchyma in the stems was found to end about 20 cm below the floral head, in summer. Bending was correlated with the extent of Sclerenchyma formation and stem lignin levels. It is concluded that stem bending is due to net water loss from the stem, particularly in the area of bending, and to low mechanical strength in the upper part of the stems, which lack a Sclerenchyma cylinder.
William Louis Stern - One of the best experts on this subject based on the ideXlab platform.
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Comparative vegetative anatomy and systematics of Laeliinae (Orchidaceae)
Botanical Journal of the Linnean Society, 2009Co-Authors: William Louis Stern, Barbara S. CarlswardAbstract:Abstract Vanilla is a pantropical genus of green-stemmed vines bearing clasping (aerial) and absorbing (terrestrial) roots. Most vanillas bear normal, thick foliage leaves; others produce fugacious bracts. Seventeen species, including both types were studied. Foliage leaves of Vanilla are glabrous, have abaxial, tetracytic stomatal apparatuses, and a homogeneous mesophyll. Species may or may not have a uniseriate hypodermis. Crystals occur in the foliar epidermises of some species, but all species have crystalliferous idioblasts with raphides in the mesophyll. Vascular bundles in leaves are collateral and occur in a single series alternating large and small. Sclerenchyma may or may not be associated with the vascular bundles. Scale leaves may be crescent or C-shaped and usually have abaxial stomatal apparatuses. A hypodermis may or may not be present; the mesophyll contains raphide bundles in idioblasts. Vascular bundles are collateral and occur in a single row sometimes aligned close to the adaxial surface. They may or may not be associated with Sclerenchyma. Stems of leafy vanillas show a Sclerenchyma band separating cortex from ground tissue; stems of leafless vanillas do not show a Sclerenchyma band. Ground tissue of the stem may consist solely of assimilatory cells or mixed assimilatory and water-storage cells. In some species centrally located assimilatory cells are surrounded by layers of water-storage cells. A uniseriate hypodermis is present in all stems. Sclerenchyma may completely surround the scattered collateral vascular bundles, occur only on the phloem side, or be absent. Both aerial and terrestrial roots are notable for their uniseriate velamen the cell walls of which may be unmarked or ornamented with anticlinal strips. Exodermis is uniseriate; the cells vary from barely thickened to strongly thickened. Only the outer and radial walls are thickened. Cortical cells of aerial roots generally have chloroplasts that are lacking from the same tissue of terrestrial roots. Raphide bundles occur in thin-walled cortical idioblasts. Endodermis and pericycle are uniseriate; pericycle cells are all ○ -thickened opposite the phloem. Cells of the endodermis are either ○- or U-thickened opposite the phloem. Vascular tissue may be embedded in thin- or thick-walled Sclerenchyma or in parenchyma. Metaxylem cells are always wider in terrestrial than in aerial roots of the same species. Pith cells are generally parenchymatous but sclerotic in a few species.
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Comparative vegetative anatomy and systematics of Cymbidium (Cymbidieae: Orchidaceae)
Botanical Journal of the Linnean Society, 2002Co-Authors: Tomohisa Yukawa, William Louis SternAbstract:The genus Cymbidium (Orchidaceae) exhibits distinctive ecological diversification and occurs in terrestrial, epiphytic, and lithophytic life forms. One species, Cymbidium macrorhizon, lacks foliage leaves and has a strongly mycoparasitic existence. Correlation between habitat differentiation and anatomical characters was tested for 21 species of Cymbidium and its putative sister groups. Although hypostomaty characterizes the genus, C. canaliculatum shows amphistomaty. Ecological preference of this species indicates that amphistomaty is likely adapted to intensive insolation. Four types of subepidermal foliar Sclerenchyma were found. Two forest floor species, C. goeringii and C. lancifolium as well as the mycoparasitic C. macrorhizon, do not have this Sclerenchyma. In this genus, development of Sclerenchyma is correlated with the degree of epiphytism. Palisade mesophyll evolved in Cymbidium section Cymbidium. As members of this section grow on isolated trees in tropical lowland forests or on rocks, the differentiation of palisade tissue is probably correlated with immigration to high light habitats. With the exception of C. macrorhizon, stegmata were found in leaves and stems of Cymbidium. Furthermore, a few epiphytic species have stegmata in their roots; this is a curious feature rarely found in vascular plants. Subterranean rhizomes characterize terrestrial species, while ageotropic roots are found in some epiphytic species. Cymbidium macrorhizon shows peculiar features such as degeneration of stomata, anomocytic stomata, and lack of stegmata and Sclerenchyma. This set of character transformations is probably correlated with the evolution of mycoparasitic existence. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 138, 383–419.
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Comparative anatomy and systematics of Catasetinae (Orchidaceae)
Botanical Journal of the Linnean Society, 2001Co-Authors: William Louis Stern, Walter S. JuddAbstract:Abstract Catasetinae consist of five genera of pseudobulbous Orchidaceae of the Neotropics. Anatomy is characterized by sunken, three-celled foliar hairs, mostly tetracytic stomatal apparatuses, superficial stomata, homogeneous mesophyll, foliar fibre bundles, collateral vascular bundles in a single row, xylem and phloem Sclerenchyma associated with vascular bundles in leaves, conical, and rough-surfaced silica bodies adjacent to vascular bundle Sclerenchyma; epidermal cells of pseudobulbs with heavily thickened outer walls, pseudobulb ground tissue of assimilatory and water-storage cells, scattered vascular bundles in pseudobulbs, and Sclerenchyma and stegmata associated only with phloem of pseudobulbs; roots with thin-walled velamen cells and tenuous spirals of cell wall material, distinctive epivelamen cells, thin-walled exodermal cells and vascular tissue embedded in parenchyma. Except for mucilaginous idioblasts that occur in Mormodes and Cycnoches , there are few outstanding anatomical differences among the five genera. Thus, there are few anatomical characteristics of phylogenetic value. The monophyly of Catasetinae is supported by the presence of sunken foliar hairs. Our results support a close relationship between Clowesia and Catasetum , and between Mormodes and Cycnoches . Among the outgroups Pteroglossaspis is especially distinctive.
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Comparative vegetative anatomy of Stanhopeinae (Orchidaceae)
Botanical Journal of the Linnean Society, 1999Co-Authors: William Louis Stern, W. Mark WhittenAbstract:Abstract Stanhopeinae are a group of tropical American orchids characterized by euglossine bee pollination and lateral inflorescences stemming from the bases of pseudobulbs. Leaves are hypostomatal, and all stomatal configurations are tetracytic. Chlorenchyma is homogeneous and characterized by fibre bundles in adaxial/abaxial or adaxial/median/abaxial positions. Collateral vascular bundles occur in a single row and feature phloic and xylic Sclerenchymatous caps and thin-walled bundle sheath cells. Fibre bundles and vascular Sclerenchyma are accompanied by stegmata containing conical silica bodies. Pseudobulbs have thick-walled turbinate epidermal cells and ground tissue of smaller, living assimilatory cells and larger, dead water-storage cells. Fibre bundles are usually absent but occur in several genera. Collateral vascular bundles show phloic Sclerenchyma, but xylic Sclerenchyma occurs only in the larger vascular bundles. Phloic and xylic Sclerenchyma are associated with stegmata containing conical silica bodies. Roots are velamentous. Velamen cell walls have fine, spiral thickenings. Exodermal cells are thin-walled. The cortex features scattered thick-walled cells and in some cases branched bars of secondary cell wall material. Endodermis is either ∪- or ○-thickened, but pericycle is always ○-thickened opposite the phloem. Vascular tissue consists of alternating strands of xylem and phloem surrounded by a matrix of thick-walled cells. Pith cells may be parenchymatous or Sclerenchymatous.
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Regular ArticleComparative vegetative anatomy and systematics of Vanilla (Orchidaceae)
Botanical Journal of the Linnean Society, 1999Co-Authors: William Louis Stern, Walter S. JuddAbstract:Vanilla is a pantropical genus of green-stemmed vines bearing clasping (aerial) and absorbing (terrestrial) roots. Most vanillas bear normal, thick foliage leaves; others produce fugacious bracts. Seventeen species, including both types were studied. Foliage leaves of Vanilla are glabrous, have abaxial, tetracytic stomatal apparatuses, and a homogeneous mesophyll. Species may or may not have a uniseriate hypodermis. Crystals occur in the foliar epidermises of some species, but all species have crystalliferous idioblasts with raphides in the mesophyll. Vascular bundles in leaves are collateral and occur in a single series alternating large and small. Sclerenchyma may or may not be associated with the vascular bundles. Scale leaves may be crescent or C-shaped and usually have abaxial stomatal apparatuses. A hypodermis may or may not be present; the mesophyll contains raphide bundles in idioblasts. Vascular bundles are collateral and occur in a single row sometimes aligned close to the adaxial surface. They may or may not be associated with Sclerenchyma. Stems of leafy vanillas show a Sclerenchyma band separating cortex from ground tissue; stems of leafless vanillas do not show a Sclerenchyma band. Ground tissue of the stem may consist solely of assimilatory cells or mixed assimilatory and water-storage cells. In some species centrally located assimilatory cells are surrounded by layers of water-storage cells. A uniseriate hypodermis is present in all stems. Sclerenchyma may completely surround the scattered collateral vascular bundles, occur only on the phloem side, or be absent. Both aerial and terrestrial roots are notable for their uniseriate velamen the cell walls of which may be unmarked or ornamented with anticlinal strips. Exodermis is uniseriate; the cells vary from barely thickened to strongly thickened. Only the outer and radial walls are thickened. Cortical cells of aerial roots generally have chloroplasts that are lacking from the same tissue of terrestrial roots. Raphide bundles occur in thin-walled cortical idioblasts. Endodermis and pericycle are uniseriate; pericycle cells are all ○ -thickened opposite the phloem. Cells of the endodermis are either ○- or U-thickened opposite the phloem. Vascular tissue may be embedded in thin- or thick-walled Sclerenchyma or in parenchyma. Metaxylem cells are always wider in terrestrial than in aerial roots of the same species. Pith cells are generally parenchymatous but sclerotic in a few species.
Zhang Li-xin - One of the best experts on this subject based on the ideXlab platform.
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Exogenously applied proline induced changes in key anatomical features and physio-biochemical attributes in water stressed oat ( Avena sativa L.) plants
Physiology and Molecular Biology of Plants, 2019Co-Authors: Rehmana Ghafoor, Nudrat Aisha Akram, Muhammad Rashid, Muhammad Ashraf, Muhammad Iqbal, Zhang Li-xinAbstract:Oat (Avena sativa) plants grown under 60% field capacity (water-deficit stress) were subjected to proline (40 mM) applied as a foliage spray. Water-deficit conditions suppressed plant growth, chlorophyll contents, leaf vascular bundle area, leaf phloem area and leaf midrib thickness, root diameter, root cortex thickness, stem diameter, stem vascular bundle area and stem phloem area. In contrast, water stress caused an increase in leaf proline, hydrogen peroxide, activities of peroxidase and superoxide dismutase enzymes, leaf bulliform cell area, leaf adaxial epidermis thickness, leaf Sclerenchyma thickness, root metaxylem area, root epidermis and endodermis area, root stelar diameter, stem Sclerenchyma thickness and stem epidermis thickness. However, exogenous application of proline significantly improved the plant growth, leaf proline contents, metaxylem area, mesophyll thickness, root diameter, root cortex thickness, root epidermis, endodermis thickness, stelar diameter, metaxylem area, stem diameter, stem vascular bundle area, stem epidermis area, stem phloem area and stem Sclerenchyma thickness. Overall, foliar spray of proline was effective in improving drought stress tolerance which can be attributed to proline-induced significant modulations in physio-biochemical and anatomical features of oat plants.
Ashraf Muhammad - One of the best experts on this subject based on the ideXlab platform.
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Exogenously applied glycinebetaine induced alteration in some key physio-biochemical attributes and plant anatomical features in water stressed oat ( Avena sativa L.) plants
Journal of Arid Land, 2019Co-Authors: Shehzadi Anum, A Akram Nudrat, Ali Ayaz, Ashraf MuhammadAbstract:Although exogenous application of glycinebetaine (GB) is widely reported to regulate a myriad of physio-biochemical attributes in plants under stressful environments including drought stress, there is little information available in the literature on how and up to what extent GB can induce changes in anatomical features in water starved plants. Thus, the present research work was conducted to assess the GB-induced changes in growth, physio-biochemical, and anatomical characteristics in two cultivars (CK-1 and F-411) of oat (Avena sativa L.) under limited water supply. After exposure to water stress, a considerable reduction was observed in plant growth in terms of lengths and weights of shoot and roots, leaf mesophyll thickness, leaf midrib thickness, root cortex thickness, root diameter, stem diameter, stem phloem area, and stem vascular bundle area in both oat cultivars. However, water stress resulted in a significant increase in leaf total phenolics, hydrogen peroxide (H2O2), ascorbic acid (AsA), GB contents, activities of enzymes (CAT, SOD and POD), total soluble proteins, leaf epidermis (abaxial and adaxial) thickness, bulliform cell area, Sclerenchyma thickness, root endodermis and epidermis thickness, root metaxylem area, stem metaxylem area and stem Sclerenchyma thickness in both oat cultivars. Foliar-applied 100 mM GB suppressed H2O2 contents, while improved growth attributes, free proline and GB contents, activity of SOD enzyme, leaf abaxial epidermis thickness, leaf bulliform cell area, leaf midrib thickness, leaf Sclerenchyma thickness, root cortex thickness, root endodermis, epidermis thickness, root stele diameter, stem diameter, stem epidermis thickness, stem metaxylem area, and stem phloem and vascular bundle area in both oat cultivars. For both oat cultivars, CK-1 was superior to F-411 in leaf abaxial epidermis thickness, leaf mesophyll, leaf Sclerenchyma, root metaxylem area, stem diameter, stem epidermis, Sclerenchyma thickness, stem metaxylem area, and stem vascular bundle area. Overall, both oat cultivars showed inconsistent behavior to water stress and foliar-applied GB in terms of different physio-biochemical attributes, however, CK-1 was superior to F-411 in a number of anatomical features of leaf, root, and stem.
Anne E Ashford - One of the best experts on this subject based on the ideXlab platform.
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investigations into seed dormancy in grevillea linearifolia g buxifolia and g sericea anatomy and histochemistry of the seed coat
Annals of Botany, 2005Co-Authors: Candida L. Briggs, E C Morris, Anne E AshfordAbstract:• Background and Aims Seeds of east Australian Grevillea species generally recruit post-fire; previous work showed that the seed coat was the controller of dormancy in Grevillea linearifolia. Former studies on seed development in Grevillea have concentrated on embryology, with little information that would allow testing of hypotheses about the breaking of dormancy by fire-related cues. Our aim was to investigate structural and chemical characteristics of the seed coat that may be related to dormancy for three Grevillea species. • Methods Seeds of Grevillea linearifolia, Grevillea buxifolia and Grevillea sericea were investigated using gross dissection, thin sectioning and histochemical staining. Water movement across the seed coat was tested for by determining the water content of embryos from imbibed and dry seeds of G. sericea. Penetration of intact seeds by Lucifer Yellow was used to test for internal barriers to diffusion of high-molecular-weight compounds. • Key Results Two integuments were present in the seed coat: an outer testa, with exo-, meso- and endotestal (palisade) layers, and an inner tegmen of unlignified Sclerenchyma. A hypostase at the chalazal end was a region of structural difference in the seed coat, and differed slightly among the three species. An internal cuticle was found on each side of the Sclerenchyma layer. The embryos of imbibed seeds had a water content six times that of dry seeds. Barriers to diffusion of Lucifer Yellow existed at the exotestal and the endotestal/hypostase layers. • Conclusions Several potential mechanisms of seed coat dormancy were identified. The embryo appeared to be completely surrounded by outer and inner barriers to diffusion of high-molecular-weight compounds. Phenolic compounds present in the exotesta could interfere with gas exchange. The Sclerenchyma layer, together with strengthening in the endotestal and exotestal cells, could act as a mechanical constraint.
