Comparative analysis of phenolic profiles of ovipositional fluid of <Emphasis Type="Italic">Rhinusa pilosa</Emphasis> (Mecinini,Curculionidae) and its host plant <Emphasis Type="Italic">Linaria vulgaris</Emphasis> (Plantaginaceae)

Rhinusa pilosa (Gyllenhal) is a highly specific weevil that induces stem galls on the common toadflax Linaria vulgaris Mill. females oviposit the eggs near the apex of a growing shoot. The act of oviposition is accompanied by secretion of an ovipositional fluid, which is considered to be cecidogen, directly involved in gall induction. The remains of cecidogenic fluid were collected from the surface of the oviposition point on the stem. We performed a comparative analysis of the phenolics extracted from cecidogen, the stem and galls of L. vulgaris and adult and larva of R. pilosa by HPLC-DAD. One compound with A _max at 273, 332 nm (R _t 30.65 min) was exclusively found in the methanol extract of cecidogen. To further characterize the cecidogen and stem phenolic profiles, we used UHPLC coupled with an OrbiTrap mass analyzer. Among 49 phenolic compounds extracted from both the ovipositional fluid and the plant, protocatechuic acid and two phenolic glycosides were exclusively found in cecidogen: diosmetin-O-acetylrutinoside and an unidentified compound. The unknown compound produced an MS² base peak at 387 and 327 and 267 m/z base peaks at MS³ and MS⁴ fragmentation, respectively, and had the molecular formula C₃₂H₃₁O₁₈. The plausible role of phenolic compounds in the induction of gall formation on L. vulgaris is discussed.     

WOUND RECOVERY BY PITH CELL REDIFFERENTIATION: STRUCTURAL CHANGES

The redifferentiation of tobacco pith cells was examined in two experimental systems: wounds recovering from an incision that severed vascular tissue of the stem, and induced differentiation of excised pith responding to indoleacetic acid supplied locally via pipets inserted into the tissue. In both systems there was an initial period during which cell division was resumed and the pith cells were cleaved into numerous small cells. This was followed by redifferentiation of some of the divided cells as tracheary elements and, especially in the stem, by the formation of a cambial meristem that produced further xylem and phloem. In the stem the size of the wound meristem decreased as the wound was made further from the shoot apex, and in the cultured pith tissue it was demonstrated that the size of the dividing zone increased with the concentration of auxin supplied. Auxin was, therefore, demonstrated to be limiting in the division phase of redifferentiation. The sequence of redifferentiation in the two experimental systems resembled the normal ontogeny of vascular tissues in the intact plant sufficiently that these systems could be used to investigate the relationship between cell differentiation and auxin transport.     

A Histopathological Study of Anomalous Growth in the Stem of Coccinia indica W. & A. Infested with Neolasioptera cephalandrae Mani

Gall formation due to attack of the larvae of Neolasiopteracephalandrae is common on the stem of Coccinia indica. Isolatedpatches of secondary meristematic centres develop throughoutthe proliferated tissue and they often differentiate into vasculartissues (either xylem or phloem or both). The larvae bore throughthe stem and live in lysigenous cavities in the ground tissue.Proliferation of cells of the secondary meristematic centresresults in gall formation and the normal vascular pattern isdisturbed and vascular bundles crushed. Development of mechanicaltissues in the affected region is suppressed. Additional cambiallayers with no definite pattern of orientation also developin the ground tissue and these produce patches of xylem tissue.Larval cavities are irregular and are surrounded by a nutritivetissue rich in protein and polysaccharides.     

侧柏扦插不定根发生模式研究

该研究以侧柏一年生硬枝插穗为实验材料,利用连续组织切片技术观察插穗不定根发生发育过程中的组织结构变化,分析插穗外部形态变化、不定根原基起源和不定根的形成过程,探讨侧柏插穗不定根发生模式和不定根的组织学起源。结果显示:侧柏扦插后可由愈伤组织、皮部诱导产生不定根,出现皮部生根、愈伤组织生根、愈伤组织兼具皮部生根3种类型;侧柏插穗中存在少量潜伏根原基,但插穗生根类型以诱导生根为主;不定根原基诱导产生于愈伤组织、木质部、形成层及次生韧皮部等部位。研究认为侧柏扦插生根属于多位点发生模式,不定根原基的组织学起源是愈伤组织、髓射线、射线原始细胞、尚未分化成熟的木质部细胞,通过人工诱导同时激活这些不定根起源位点能够显著提高生根率和生根质量。     

Biology and host specificity of Rhinusa pilosa,a recommended biological control agent of Linaria vulgaris

Linaria vulgaris Mill. (Plantaginaceae), common or yellow toadflax, is a Eurasian short-lived perennial forb invasive throughout temperate North America. Rhinusa pilosa (Gyllenhal) (Coleoptera, Curculionidae) is a univoltine shoot-galling weevil found exclusively on L. vulgaris in Europe. Under no-choice test conditions, 13 non-native Linaria species exposed to R. pilosa were accepted for oviposition and most were found to be suitable, to varying degrees, for gall and larval development. Adult feeding and survival was minimal on native North American species in the plant tribe Antirrhineae which includes the target plant. In no-choice tests with 63 native North American species and 24 other non-target species outside Linaria, oviposition was limited to four native North American species. Only three larvae developed to the adult stage on Sairocarpus virga (A. Gray) D.A. Sutton, with no negative impact on plant growth. Risks to native flora from the release of R. pilosa are therefore expected to be minimal. The Technical Advisory Group for the Biological Control of Weeds (TAG—BCW) has recommended release of R. pilosa in September 2013.     

Pattern of cell division and wound vessel member differentiation in coleus pith explants

When pith parenchyma explants are taken from Coleus blumei plants and cultured on an agar medium containing sucrose and indoleacetic acid wound vessel members differentiate in 10 days. The time course of wound xylem appearance and an auxin requirement suggest that this uncomplicated system is responding in a manner comparable to wounded Coleus plants and cultured stem segments.

Histological examination and cell size comparisons confirm that parenchyma cells divide before differentiating. When colchicine is used to prevent mitosis no tracheary elements differentiate. Following the time course of this cytodifferentiation histologically shows that xylem differentiates from cells that are the products of several cell divisions.

     

DEVELOPMENTAL ANATOMY OF THE HORNED OAK GALL INDUCED BY CALLIRHYTIS CORNIGERA ON QUERCUS PALUSTRIS (PIN OAK)

The horned oak gall forms on twigs of Quercus palustris Muench. and is initiated when the wasp Callirhytis corrigera O.S. oviposits into the periderm or cortex of the twigs. Injury to phellogen as a consequence of oviposition results in dedifferentiation of phelloderm and underlying phloem tissue to form a wound-response phellogen. The wound-response phellogen encircles and compartmentalizes the wasp ovum and is continuous with the normal stem phellogen. This tissue arrangement forms the framework for the ensuing stages of gall development. Development of the insect larva coincides with the formation of a gall-matrix phellogen. This additional meristem is derived from locally hyperplastic stem phellogen where adjacent to the wound-response phellogen. The essentially parenchymatous, roughly spherical body of the gall, the gall matrix, is formed chiefly from derivatives of the gall-matrix and wound-response phellogens. In the immediate area of the wasp larva, the wound-response phellogen produces cells toward the larva that differentiate to form a vascularized, externally sclerified, horn-shaped chamber containing in its base the developing insect larva. The involvement of the vascular cambium is apparent during intermediate gall development stages. Vascular strands, produced transverse to the stem axis, penetrate the gall-matrix tissue and terminate near the base of the horn-like larval chamber. Vessel elements in the region of the gall that are not included in this tissue alteration often become heavily tylosed. Disruption of the vascular tissue through the galled area appears to be a primary cause of twig death.     

Defense response of resistant host Impatiens balsamina to the parasitic angiosperm Cuscuta japonica

The response of the stem of a resistant host (Impatiens baslamina) to infection by the parasitic flowering plant Cuscuta japonica was studied with light and electron microscopy. The intra- and interfascicular cambial cells in the host stem first reacted to the penetrating upper haustorium by dividing, and the differentiation of the host xylem (vascular) tissues proceeded toward interfascicular areas from vascular bundles. When the host vascular tissue was invaded by the endophyte (haustorial portion in the host stem), the host xylem was displaced, and host vessels became occluded with parenchyma cells, resulting in tyloses. As the parasitism progressed, areas of the host stem penetrated by the endophyte became swollen via secondary growth and cell division in the parenchymatous cortex, pith, and interfascicular areas. During this intrusion by the endophyte, darkly stained necrotic reactions were detected at the interface between the host tissue and the invading endophyte. The results suggested that in the host tissues penetrated by the parasite, the formation of secondary tissue and swellings caused by active cell division of ground tissue and host vessel occlusion by tyloses constitute the host structural defense against the parasite.     

Biomechanics of the columnar cactus Pachycereus pringlei

We report the longitudinal variations in stiffness and bulk density of tissue samples drawn from along the length of two Pachycereus pringlei plants measuring 3.69 and 5.9 m in height to determine how different tissues contribute to the mechanical stability of these massive vertical organs. Each of the two stems was cut into segments of uniform length and subsequently dissected to obtain and mechanically test portions of xylem strands, stem ribs, and a limited number of pith and cortex samples. In each case, morphometric measurements were taken to determine the geometric contribution each tissue likely made to the ability of whole stems to resist bending forces. The stiffness of each xylem strand increased basipetally toward the base of each plant where stiffness sharply decreased, reaching a magnitude comparable to that of strands 1 m beneath the stem apex. The xylem was anisotropic in behavior, i.e., its stiffness measured in the radial and in the tangential directions differed significantly. Despite the abrupt decrease in xylem strand stiffness at the stem base, the contribution made by this tissue to resist bending forces increased exponentially from the tip to the base of each plant due to the accumulation of wood. A basipetal increase in the stiffness of the pith (and, to limited extent, that of the cortex) was also observed. In contrast, the stiffness of stem rib tissues varied little as a function of stem length. These tissues were stiffer than the xylem in the corresponding portions of the stem along the upper two-fifths of the length of either plant. Tissue stiffness and bulk density were not significantly correlated within or across tissue types. However, a weak inverse relationship was observed for these properties in the case of the xylem and stem rib tissues. We present a simple formula that predicts when stem ribs rather than the xylem strands serve as the principal stiffening agents in stems. This formula successfully predicted the observed aspect ratio of the stem ribs (the average quotient of the radial and tangential dimensions of rib transections), and thus provided circumstantial evidence that the ribs are important for mechanical stability for the distal and younger regions of the stems examined.     

白鲜营养器官解剖结构及其与白鲜碱的积累关系

应用植物解剖学、组织化学及植物化学方法对白鲜营养器官根、茎、叶的结构及其生物碱的积累进行了研究。结果显示:(1)白鲜根的次生结构以及茎和叶的结构类似一般双子叶植物;白鲜多年生根主要由周皮、次生韧皮部、维管形成层以及次生木质部组成,根次生韧皮部中可见大量的淀粉、草酸钙簇晶、韧皮纤维以及油细胞;茎由表皮、皮层、维管组织和髓组成;叶由表皮、栅栏组织、海绵组织和叶脉组成;在茎和叶初生韧皮部的位置均分布有韧皮纤维,在叶表皮上分布有头状腺毛和非腺毛;在茎和叶紧贴表皮处分布有分泌囊。(2)组织化学分析结果显示:在白鲜多年生根中,生物碱类物质主要分布在周皮、次生韧皮部、维管形成层和木薄壁细胞中;在茎中,生物碱主要分布在表皮、皮层、韧皮部、木薄壁细胞及髓周围薄壁细胞中;在叶中,生物碱主要分布在表皮细胞、叶肉组织和维管组织的薄壁细胞;此外在分泌囊和头状腺毛中亦含有生物碱类物质。(3)植物化学结果显示,秦岭产白鲜根皮/白鲜皮、根木质部、茎和叶中白鲜碱含量分别为0.041%、0.012%、0.004%和0.002%,其中木质部中白鲜碱含量和其他部分地区白鲜皮中白鲜碱含量类似。研究表明,在秦岭产白鲜营养器官中,除根皮/白鲜皮外,在根木质部亦含有大量的白鲜碱,且在茎和叶中亦含有一定的白鲜碱,具有潜在的开发利用价值。     

Radial secondary growth and formation of successive cambia and their products in Ipomoea hederifolia L. (Convolvulaceae)

Ipomoea hederifolia stems increase in thickness using a combination of different types of cambial variant, such as the discontinuous concentric rings of cambia, the development of included phloem, the reverse orientation of discontinuous cambial segments, the internal phloem, the formation of secondary xylem and phloem from the internal cambium, and differentiation of cork in the pith. After primary growth, the first ring of cambium arises between the external primary phloem and primary xylem, producing secondary phloem centrifugally and secondary xylem centripetally. The stem becomes lobed, flat, undulating, or irregular in shape as a result of the formation of both discontinuous and continuous concentric rings of cambia. As the formation of secondary xylem is greater in one region than in another, this results in the formation of a grooved stem. Successive cambia formed after the first ring are of two distinct functional types: (1) functionally normal successive cambia that divide to form secondary xylem centripetally and secondary phloem centrifugally, like other dicotyledons that show successive rings, and (2) abnormal cambia with reverse orientation. The former type of successive rings originates from the parenchyma cells located outside the phloem produced by previous cambium. The latter type of cambium develops from the conjunctive tissue located at the base of the secondary xylem formed by functionally normal cambia. This cambium is functionally inverted, producing secondary xylem centrifugally and secondary phloem centripetally. In later secondary growth, xylem parenchyma situated deep inside the secondary xylem undergoes de‐differentiation, and re‐differentiates into included phloem islands in secondary xylem. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 30–40.     

Histopathogenesis of the Galls Induced by Nothanguina phyllobia in Solanum elaeagnifolium

The histopathogenesis of the foliar galls induced by Nothanguina phyllobia Thorne in Solanum elaeagnilolium Cav. was examined via serial sections prepared from plant shoots at 11 time intervals (0.5-30 days) following inoculation. Nematodes infected the blades and petioles of young leaves surrounding the shoot apex. Hypertrophy and hyperplasia of the palisade, pith, cortical, and vascular parenchyma resulted in the formation of confluent leaf, petiole, and stem galls up to 25 cm³ in volume. Externally, leaf galls were irregular, light-green, convoluted spheroid bulges distending the abaxial surface. Mature galls contained a cavity lined with parenchymogenous nutritive tissue comprising intercellular spaces and actively dividing hypertrophied cells. These cells contained granular cytoplasm, hypertrophied nuclei, and brightly stained large nucleoli. Vascular tissues were not discernibly affected during the early stages of gall development. As gall development progressed, however, vascular elements were often displaced and disoriented. The histopathology of this nematode indicates that N. phyllobia is a highly specialized parasite and, for that reason, is suitable as a biological control agent.     

Ice formation and tissue response in apple twigs

Abstract. The response of apple twig tissue to a freezing stress was examined using a combination of low temperature scanning electron microscopy and freeze substitution techniques. Bark and wood tissues responded differently. In the bark, large extracellular ice crystals were observed in the cortex. The adjacent cortical cells collapsed and a large reduction in cell volume was observed. The extent of cell collapse throughout the bark was not uniform. Cells in the periderm, phloem and cambium exhibited little change in cell volume compared to cortical cells. Large extracellular ice crystals were not observed in the xylem or pith tissues. The xylem ray parenchyma and pith cells did not collapse in response to a freezing stress, but retained their original shape. The pattern of ice formation and cell response was not observed to change with season or the level of cold acclimation. This study supported the concept that bark and xylem tissues exhibit contrasting freezing behaviour. The observations were consistent with the idea that water in bark freezes extracellularly while water in xylem ray parenchyma and pith cells may supercool to temperatures approaching –40 °C prior to freezing intracellularly.     

Anatomical adaptations of Astragalus gombiformis Pomel. under drought stress

The present study was designed to study the effect of drought on root, stem and leaf anatomy of Astragalus gombiformis Pomel. Several root, stem and leaf anatomical parameters (cross section diameter, cortex, root cortical cells, pith, leaf lamina and mesophyll thickness) were reduced under moderate to severe water deficit (20–30 days of withheld irrigation). The stele/cross section root ratio increased under moderate water deficit. The root’s and stems vascular systems showed reduced xylem vessel diameter and increased wall thickness under water deficit. In addition, the root xylem vessel density was increased in these drought conditions while it was unchanged in the stems. The stomata density was increased under prolonged drought conditions whereas the stomata size was untouched. The leaf vascular system showed reduced xylem and phloem tissue thickness in the main vein under moderate to severe water deficit. However, in the lamina the vascular tissue and the distance between vascular bundle were unaffected. Our findings suggest a complex network of anatomical adaptations such as a reduced vessel size with increased wall thickness, lesser cortical and mesophyll parenchyma formation and increased stomata density. These proprieties are required for the maintenance of water potential and energy storage under water stress which can improve the resistance of A. gombiformis to survive in arid areas.     

Histological Comparisons of Fergusobia/Fergusonina-Induced Galls on Different Myrtaceous Hosts

The putative mutualism between different host-specific Fergusobia nematodes and Fergusonina flies is manifested in a variety of gall types involving shoot or inflorescence buds, individual flower buds, stems, or young leaves in the plant family Myrtaceae. Different types of galls in the early-to-middle stages of development, with host-specific species of Fergusobia/Fergusonina, were collected from Australian members of the subfamily Leptospermoideae (six species of Eucalyptus, two species of Corymbia, and seven species of broad-leaved Melaleuca). Galls were sectioned and histologically examined to assess morphological changes induced by nematode/fly mutualism. The different gall forms were characterized into four broad categories: (i) individual flower bud, (ii) terminal and axial bud, (iii) ''basal rosette'' stem, and (iv) flat leaf. Gall morphology in all four types appeared to result from species-specific selection of the oviposition site and timing and number of eggs deposited in a particular plant host. In all cases, early parasitism by Fergusobia/Fergusonina involved several layers of uninucleate, hypertrophied cells lining the lumen of each locule (gall chamber where each fly larva and accompanying nematodes develop). Hypertrophied cells in galls were larger than normal epidermal cells, and each had an enlarged nucleus, nucleolus, and granular cytoplasm that resembled shoot bud gall cells induced by nematodes in the Anguinidae.     

Isolation of the abdomen releases oviposition behaviour in females of the cricket, Acheta domesticus

Upon isolation, abdomens of adult female house crickets (Acheta domesticus) produced abdominal and ovipositor movements characteristic of normal oviposition. Oviposition behaviour was thus released even in reproductively mature or immature virgins where under normal conditions it was never observed. Decapitation was not sufficient to release oviposition behaviour but transection of the ventral nerve cord between the thorax and the abdomen of immobilized females evoked the response. These observations indicate that the motor programmes for certain components of the oviposition sequence reside in the abdominal ganglia. Moreover, the prerequisite circuitry for ovipositional posturing of the abdomen and ovipositor appears to be functional prior to sexual maturity and insemination, primed by mating, and subject to inhibition by the thoracic ganglia.     

Fungal diversity in galls of baldcypress trees

The baldcypress midge (Taxodiomyia cupressi and Taxodiomyia cupressiananassa) forms a gall that originates from leaf tissue. Female insects may inoculate galls with fungi during oviposition, or endophytes from the leaf tissue may grow into the gall interior. We investigated fungal diversity inside of baldcypress galls, comparing the gall communities to leaves and comparing fungal communities in galls that had successful emergence versus no emergence of midges or parasitoids. Galls of midges that successfully emerged were associated with diverse gall fungal communities, some of which were the same as the fungi found in surrounding leaves. Galls with no insect emergence were characterized by relatively low fungal diversity.     

Movement to bark and metabolism of xylem cytokinins in stems of Lupinus angustifolius

Following uptake of [(3)H]zeatin riboside and [(3)H]dihydrozeatin riboside by girdled lupin (Lupinus angustifolius L.) stems via the transpiration stream, rapid lateral movement of the radioactivity from xylem to bark was observed. Short-term studies with intact stems, and other studies with excised stem tissues, revealed that the ribosides and/or the corresponding nucleotides were the cytokinin forms which actually moved into the bark tissues. Relative to cytokinin metabolism in xylem plus pith, metabolism in bark was both more rapid and more complex. Riboside cleavage and formation of the O-acetylzeatin and O-acetyldihydrozeatin ribosides and nucleotides were almost completely confined to bark tissues. Exogenous (3)H-labelled O-acetylzeatin riboside was converted to zeatin riboside in bark tissue, but the presence of the acetyl group suppressed degradation to adenine metabolites. The sequestration and modification of xylem cytokinins by stem tissues probably contributes significantly to the cytokinin status of the shoot. New cytokinins identified by mass spectrometry in lupin were: O-acetyldihydrozeatin 9-riboside, a metabolite of exogenous dihydrozeatin riboside in stem bark; O-methylzeatin nucleotide and O-methyldihydrozeatin 9-riboside, metabolites of endogenous cytokinins in stem bark; O-methylzeatin nucleotide and O-methylzeatin 9-riboside, metabolites of exogenous zeatin riboside in excised pod walls.     

STRUCTURALLY PRESERVED FOSSIL PLANTS FROM ANTARCTICA. I. ANTARCTICYCAS,GEN. NOV., A TRIASSIC CYCAD STEM FROM THE BEARDMORE GLACIER AREA

Silicified stems with typical cycadalean anatomy are described from specimens collected from the Fremouw Formation (Triassic) in the Transantarctic Mountains of Antarctica. Axes are slender with a large parenchymatous pith and cortex separated by a narrow ring of vascular tissue. Mucilage canals are present in both pith and cortex. Vascular tissue consists of endarch primary xylem, a narrow band of secondary xylem tracheids, cambial zone, and region of secondary phloem. Vascular bundles contain uni- to triseriate rays with larger rays up to 2 mm wide separating the individual bundles. Pitting on primary xylem elements ranges from helical to scalariform; secondary xylem tracheids exhibit alternate circular bordered pits. Traces, often accompanied by a mucilage canal, extend out through the large rays into the cortex where some assume a girdling configuration. A zone of periderm is present at the periphery of the stem. Large and small roots are attached to the stem and are conspicuous in the surrounding matrix. The anatomy of the Antarctic cycad is compared with that of other fossil and extant cycadalean stems.     

THE RELATIONSHIP BETWEEN THE PRIMARY THICKENING MERISTEM AND THE SECONDARY THICKENING MERISTEM IN YUCCA WHIPPLEI TORR. I. HISTOLOGY OF THE MATURE VEGETATIVE STEM

Anatomical observations were made on 1-, 2-, and 3-yr-old plants of Yucca whipplei Torr, ssp. percursa Haines grown from seed collected from a single parent in Refugio Canyon, Santa Barbara, California. The primary body of the vegetative stem consists of cortex and central cylinder with a central pith. Parenchyma cells in the ground tissue are arranged in anticlinal cell files continuous from beneath the leaf bases, through the cortex and central cylinder to the pith. Individual vascular bundles in the primary body have a collateral arrangement of xylem and phloem. The parenchyma cells of the ground tissue of the secondary body are also arranged in files continuous with those of the primary parenchyma. Secondary vascular bundles have an amphivasal arrangement and an undulating path with frequent anastomoses. Primary and secondary vascular bundles are longitudinally continuous. The primary thickening meristem (PTM) is longitudinally continuous with the secondary thickening meristem (STM). Axillary buds initiated during primary growth were observed in the leaf axils. The STM becomes more active prior to and during root initiation. Layers of secondary vascular bundles are associated with root formation.