Observations on Companion Cells and Specialized Phloem Parenchyma Cells of Nelumbo nucifera Gaertn

The phloem of very young petioles of Nelumbo nucifera Gaertn.(Nelumbium speciosum Willd.) was studied with the light microscope.The elongated, mature sieve elements contain slime, plugs, strands,and numerous plastids. Some sieve elements remain nucleatedfor a brief period even after the sieve plates are well developed.The companion cells numbering 8–14 undergo disintegrationbefore the elongation of the ontogenetically related sieve elementis completed. They are uninucleate to begin with but later becomebinucleate and finally degenerate and obliterate. The variousstages in their ontogeny and disintegration are described. Ofthe very few specialized phloem parenchyma cells present, someare associated with sieve elements. They have slime body-likestructures, and plastid-like bodies which group together andeventually disintegrate.     

Some Effects of Temperature and Substrate Content upon Respiration and the Carbon Balance of Field Beans (Vicia faba L.)

The effects of substrate content and temperature upon the productionof carbon dioxide in the dark were investigated in Vicia fabaand Sorghum vulgare, using the time courses for carbon dioxiderelease. No endogenous rhythms were found. With V. faba at highsubstrate contents, a steady rate of respiration was measuredat low temperatures, suggesting that the rate of respirationis limited by a third factor such as enzyme activity. This steadyrate eventually decreased rapidly. There was a first order rateof decrease with time at higher temperatures. Low substratecontents gave a complex decay. The rate of decrease of the rateof respiration was affected by the initial state of the plantsover the same range of rates. Reasons for this are discussed.The temperature sensitivity of respiration was investigated.The respiration of plants with high substrate contents had alower temperature sensitivity than those with low substratecontents. This was further investigated by measuring the stoichiometryof carbon dioxide production in the dark from total solublecarbohydrate (as hexose equivalent). It is likely that incompletehexose respiration, which occurs at high substrate contents,is less temperature sensitive than complete hexose respirationor the respiration of some other substrate. Vicia faba, Sorghum oulgare, carbon dioxide, respiration, temperature, substrate content     

Cellular Differentiation in a Highly Specialized Insect Secretory Organ

The colleterial glands of insects are accessory reproductive structures which produce secretions that are applied to eggs after fertilization and which serve a number of protective functions. The colleterial glands of lepidoptera are of particular interest in the study of the events of cellular differentiation because they undergo rapid development, generally during the pupal adult transformation, and contain highly specialized cells which produce large amounts of a restricted variety of secretory products. The extreme specialization of these organs facilitates parallel studies of differentiation at the biochemical and morphological level. This communication describes the changes in the ultrastructure of cells which will form the protein-secreting segment of the colleterial gland of the moth Actias luna during the period of transition from the undifferentiated state to the acquisition of secretory ability.
An initial stage of general cellular proliferation by mitosis in the presumptive colleterial tissue mass is followed by differentiation of the cells in the absence of further mitosis. Four distinctive cell types are recognized during the phase of differentiation. These types include a chitogenous cell which forms the chitin lining of the main duct, and three cells which cooperate in the formation of a secretory apparatus. Cell A forms two temporary flagella-like structures which assist in the formation of a ductule, which eventually leads from the secretory cell to the main duct. Near the end of the differentiative phase, Cell A degenerates and is phagocitized by Cell B. Cell B becomes the actual secretory element, and acquires cytoplasmic features such as extensive rough endoplasmic reticulum and Golgi apparatus which are associated with synthesis and secretion of protein. The final element, Cell C, remains associated with the ductule which it helps to construct and which traverses its cytoplasm.     

Distribution of Photosynthetic Enzymes between Mesophyll, Specialized Parenchyma and Bundle Sheath Cells of Arundinella hirta

Arundinella hirta L. is a C₄ plant having an unusual C₄ leaf anatomy. Besides mesophyll and bundle sheath cells, A. hirta leaves have specialized parenchyma cells which look morphologically like bundle sheath cells but which lack vascular connections and are located between veins, running parallel to them. Activities of phosphoenolpyruvate and ribulose-1,5-bisphosphate carboxylases and phosphoenolpyruvate carboxykinase, NADP-and NAD-malic enzymes were determined for whole leaf extracts and isolated mesophyll protoplasts, specialized parenchyma cells, and bundle sheath cells. The data indicate that A. hirta is a NADP-malic enzyme type C₄ species. In addition, specialized parenchyma cells and bundle sheath cells are enzymatically alike. Compartmentation of enzymes followed the C₄ pattern with phosphoenolpyruvate carboxylase being restricted to mesophyll cells while ribulose-1,5-bisphosphate carboxylase and decarboxylating enzymes were restricted to bundle sheath and specialized parenchyma cells.     

A Study of 'Phloeotracheids' in Haustoria of Santalaceous Root Parasites using Scanning Electron Microscopy

Tracheary elements within haustoria of six santalaceous rootparasites have been examined by scanning electron microscopywith particular reference to those cells which contain granules.These cells have been called ‘phloeotracheids’ byearly workers. The granules lie free within the lumen of thecell from which a protoplast is absent at maturity. The granulesoccur in short vessel elements and in imperforate cells whichare thought to represent a specialized type of tracheid. Phloeotracheidsare confirmed in Exocarpus bidwilliiand Mida salicifolia andreported for the first time in Buckleya distichophylla, Comandraumbellata, Nestronia umbellataand Pyrularia pubera. The structureof phloeotracheids shown by scanning electron microscopy isdiscussed in relation to previous studies.     

The Ultrastructure and Analytical Microscopy of Silicon Deposition in the Intercellular Spaces of the Roots of Molinia caerulea (L.) Moench

Silicon accumulation in mature roots of Molinia caerulea (L.)Moench. was investigated by transmission electron and Cora analyticalmicroscopy. Deposits are located in the intercellular spaces(ICS) of the persistent cortical cells immediately externalto the endodermis. The earliest deposits are in the form ofspheres lining the cavities and are followed by further depositswhich eventually fill the ICS. Evidence is presented that priorto and during the earliest silicon formations, many ICS revealedthe presence of cell organelles. No silicon was detected inthe inner tangential walls of the endodermis. The results are discussed in relation to previous studies ofsilicon deposits in the roots of Molinia and to possible pathwaysresulting in deposits associated with the ICS. Molinia caerulea(L.) Moench, roots, silicon deposition, analytical microscopy     

Patterns of Endopolyploidy During Seedling Development in Cabbage (Brassica oleracea L.)

Flow cytometric analysis of nuclear DNA contents of somatictissues of cabbage (Brassica oleracea L.) has revealed extensiveendopolyploidization, resulting in tissues that comprise mixturesof cells with different DNA contents, ranging from 2C to 16C.Patterns of endopolyploidy are specific to each developmentalstage. Multiple polyploidy was not present in the embryos ofdry seeds. Rapid endoreduplication occurred in the radicle andthe hypocotyl of the embryos during seed germination. Furtherendoreduplication cycles were detected in all tissues exceptthose of the shoot tips. In five cabbage cultivars tested, seedlingscontained cells of four ploidy levels, corresponding to 2C,4C, 8C and 16C. Multiploidy may be an integral part of differentiationprograms in cabbage plants. The biological significance of endoreduplicationin cabbage plants is discussed. Copyright 2001 Annals of BotanyCompany Cabbage (Brassica oleracea L.), endopolyploidy, endoreduplication, flow cytometry     

Multiple Mechanisms Provide Tolerance to Environmental Sulfide in Urechis caupo

SYNOPSIS. During tidal exposure the echiuran worm Urechis caupoencounters toxic sulnde in its burrow microhabitat on the marinemudflat. Although sulnde freely penetrates the two respiratoryepithelia (the body wall and hindgut) and tissue cytochromeoxidases are extremely sulnde sensitive, the worm toleratessulnde concentrations which exceed environmental exposures.Sulnde tolerance results from a suite of sulnde detoxificationmechanisms that extend from the coelomic fluid to the epithelialsurfaces. The coelomic fluid is rich in hemoglobin and hematin,both of which bind sulfide and catalyze the oxidation of sulfideto thiosulfate in vitro. Peripheral defense mechanisms responsiblefor protection of aerobic epithelia from sulfide poisoning mayinclude mucus secretion, sulfide oxidation by symbiotic bacteriaand/or specialized organelles termed SOBs, and sloughing ofsulfide damaged cells. Thiosulfate, the principal detoxificationendproduct produced in vivo, is eliminated primarily by diffusionacross the hindgut, and sulfur metabolites may be sequesteredand eliminated by the anal sacs. Based on a hypothetical model,we conclude that sulfide tolerance in U. caupo is due primarilyto the sulfide oxidation activity of the coelomic fluid andthat the specialized integument and hindgut protect the metabolicallyactive, sulfide-exposed epithelial cells. These sulfide detoxificationmechanisms may allow populations of this filter-feeding wormto exploit nutrient-rich, sulfidic environments.     

Anthocyanin Influence on Water Proton NMR Relaxation Times and Water Contents in Leaves of Evergreen Woody Plants During the Winter

An investigation was made to determine the effect of anthocyaninin red-colored evergreen leaves during the mid-winter on waterproton NMR relaxation times (T₁). Water contents, anthocyanincontentsand histologic localization of red-coloration in mesophyllswere determined by using both red-colored and green leaves fromthe same branches of Rhododendron, Viburnum and Mahonia, respectively.Although the decrease of water contents in the red-colored leavesin Mahonia was insignificant, decreases in the former two specieswere clearly observable. T₁ differences between red-coloredand green leaves for the three species were insignificant. Increasesof anthocyanin contents and histologic localization of red colorationin mesophylls for the red-colored leaves were more pronouncedin Rhododendron and Viburnum than in Mahonia. These observationssuggest that the pronounced increases of histologic localizationof red-colored mesophyll cells and anthocyanin contents in red-coloredleaves for the former two species contribute to maintenanceof T₁ relaxation times in spite of the marked decrease of watercontents in leaves. It is assumed that the increase of localizationareas of red-colored parenchymatous cells in mesophylls is moreeffective than the total contents of anthocyanins in leavestowards the maintenance of the T₁ level in red-colored leaves,and this appears to be dependent on the vacuolar compartmentationof anthocyanin in mesophyll cells. (Received August 3, 1991; Accepted December 12, 1991)     

Development of Chlorenchyma and Window Tissues in Leaves of Peperomia columella

Window leaves consist primarily of tissues specialized for waterstorage (window tissue) and photosynthesis (chlorenchyma). Theobjective of our research was to determine when these specializationsoccur during leaf development in Peperomia columella, a succulentwindow plant, native to deserts of South America. We measuredabsolute and relative volumes of leaf tissues. Young leavesconsist of approximately 75% chlorenchyma and 12% window tissue,suggesting that they are structurally specialized primarilyfor photosynthesis rather than water storage. In mature leavesthe percentages of chlorenchyma and window tissue are approximately20% and 58%, respectively, indicating that specialization forwater storage occurs during later stages of leaf development.The percent window tissue decreases in mature leaves, but increasesin young leaves with water stress.Copyright 1993, 1999 AcademicPress Chlorenchyma, Peperomia columella, succulent, window plant     

Ultrastructure, Origin, and Composition of the Protein Bodies in the Ligule of Isoetes lacustris L.

The basal cells in the ligule of Isoetes lacustris contain numerousprotein bodies, the contents of which can be digested enzymicallyby pronase and are stained red by treatment with ninhydrin Schiff'sreagent. Two types of protein bodies can be distinguished ultrastructurally:spherically-shaped bodies with granular contents and spindle-likebodies with fibrillar contents. Both are ensheathed by singlemembranes and do not show any solid inclusions within theirmatrix. The protein bodies probably arise from dilatation of the endoplasmicreticulum (ER) cisternae. This conclusion is based upon threeobservations: (a) The protein bodies occasionally show membranecontinuity with the ER; (b) ribosomes and polysomes are frequentlyattached to the protein-body membranes; (c) the contents ofthe protein bodies and of the dilated ER cisternae show similarultrastructural features. The dilatation of the ER cisternae is assumed to be a resultof protein accumulation in the intracisternal space. Based upon the results of polyacrylamide gel electrophoresis,it is likely that the spherically-shaped protein bodies storepredominately two proteins with molecular weights of 51300 and55800 D, while the spindle-like bodies store two proteins withmolecular weights of 92000 and 98000 D. The results presented do not permit a definite conclusion regardingthe function of the ligule of Isoetes lacustris but it is suggestedthat it may have a nutritive role. Isoetes lacustris L., ligule, protein bodies, endoplasmic reticulum, ultrastructure     

Changes in Triterpenoid Content during the Growth Cycle of Cultured Plant Cells

Similar changes in the pentacyclic triterpenoid contents wereobserved during the growth cycle of Datura innoxia, Luffa cylindricaand Lycopersicon esculentum seedling callus cells in batch culture.Triterpenoid contents decreased for several days after callusinoculation, then increased rapidly during the mid and lateexponential phases of growth. (Received May 28, 1984; Accepted September 13, 1984)     

Changes in cytochrome contents and respiratory activity of Bacillus cereus Strain T during germination, vegetative growth and sporulation

Vegetative cells of Bacillus cereus Strain T contain cytochromeb-562, a minor b-type component, in addition to known components,cytochrome a+a₃, cytochrome b-557 and cytochrome c-551. Also,the spores contain low but definite amounts of cytochromes b-562and c-551, which were oxidized when the spores were shaken withair. Contents of cytochromes a, b and c per cell and per cellnitrogen, and the activity of glucose oxidation increased duringspore germination and elongation. During the stage precedingfirst cell division, cytochrome contents per cell increasedin parallel with the increase of cell nitrogen, while the activityof glucose oxidation decreased. During early exponential growth,the content of cytochrome b per cell nitrogen and respiratoryactivity with glucose again increased. When cells entered thesporulation stage, characterized by structural changes insidethe cells, the activity of glucose oxidation began to decrease,while that of acetate or succinate oxidation started to increase.During the sporulation process, the contents of the three cytochromecomponents continued to increase and reached the highest levelin cells containing completed spores, but the activity of respirationwith endogenous or added substrates was negligible in thesecells. (Received November 10, 1975; )     

Antigenic Similarity in Urate Oxidases of Major Ureide Producing Legumes and Its Correlation with the Type of Peroxisome in Uninfected Cells of Nodules

Structural, biochemical, and immunological comparisons of nodulesfrom ten species of plants were made to determine if a correlationexists between nodule structure, ureide production, urate oxidaseactivity, and antigenic similarity in urate oxidase. In specieswith high urate oxidase activity and cross-reaction with soybeananti-urate oxidase [soybean (Glycine max), green bean (Phaseolusvulgaris), mung bean (Vigna radiata), cowpea (Vigna unguiculata)],the nodules were determinate and contained numerous interstitialcells, interspersed among the infected cells. Within the interstitialcells of the ureide producing nodules numerous peroxisomes werenoted and these peroxisomes appear to be structurally similar,viz. a large electron opaque core surrounded by a less electronopaque rim. Although hemp sesbania (Sesbania exaltata) noduleswere similar in ultrastructure to other ureide producers withdetectable urate oxidase activity, no cross-reactivity was observedwith anti-soybean urate oxidase. Amide producing nodules eithercontained no interstitial cells [e.g. Indian jointvetch (Aeschynomeneindica), showy crotalaria (Crotalaria spectabilis)} or interstitialcells with few peroxisomes [e.g. alfalfa (Medicago saliva),broad bean (Vicia faba), pea (Pisum sativum)] with little urateoxidase activity, exhibiting no cross-reaction with soybeananti-urate oxidase. These data indicate that the urate oxidasein most ureide producing nodules is very similar and, structurally,ureide producing nodules are organized in a specialized wayto carry out ureide assimilation in the uninfected interstitialcells. (Received June 19, 1986; Accepted January 12, 1987)     

Unusual Tissue Complexes Formed in Association with Traumatic Gum Cavities in the Stem of Bombax ceiba L.

Administration of ethephon (2-chloroethyl phosphonic acid) inthe stem of Bombax ceiba L. (Bombacaceae) induced the formationof a barrier zone of several layers of traumatic parenchymacells from the vascular cambium. These cells accumulate polysaccharidesand phenolics at irregular intervals, and eventually break downinitiating a gum cavity. The lysis of cells proceeds in a definiteway keeping characteristic islands of parenchyma intact in thetraumatic tissue. So the traumatic parenchyma is organized intoseveral large horizontal conical projections of uniform shapeand cell composition amidst the tangentially anastamosing cavities.The projections have a central core of radially elongated cellsand a few layers of peripheral cambiform cells. The derivativesof the cambiform cells enlarge, accumulate polysaccharides andphenolics, and disintegrate in the cavity. Later, disintegrationof some of the projections further enlarges the cavity. Bombax ceiba, ethephon, gum cavities, unusual tissue complexes     

Stomatal Features in the Leaf of Aganosma dichotoma (Roth) K. Schum

Paracytic and anisocytic types of mature stomata are found inthe leaf of Aganosma dichotoma. Stomata with one guard cell,stomata with degenerated guard cells, and contiguous stomataare common. Stomata with arrested pore development are alsofound in certain cases. A single guard cell without any porehas not been designated as a stoma with one guard cell in thepresent investigation. Ontogeny of contiguous stomata have beentraced. Subsidiary cells are, morphologically, just like theircontiguous guard cells. Subsidiary cells may retain their shapeand contents even when their contiguous stoma becomes mature,or may change their shape and lose their contents. They mayor may not divide. Subsidiary cells form a whorl of more thantwo subsidiary cells around a stoma by their divisions. Degenerationof guard cell(s)— their contents and nuclei—havebeen traced. In certain cases guard cells divide forming morethan two guard cells associated to a single pore. Cytoplasmicconnections are found between two guard cells of nearby stomata,and between a guard cell and an epidermal cell. Near the wound,the epidermal cells over the veins become meristermatic givingrise to new epidermal cells but no meristemoid.     

Specialized Yeast Ribosomes: A Customized Tool for Selective mRNA Translation

Evidence is now accumulating that sub-populations of ribosomes - so-called specialized ribosomes - can favour the translation of subsets of mRNAs. Here we use a large collection of diploid yeast strains, each deficient in one or other copy of the set of ribosomal protein (RP) genes, to generate eukaryotic cells carrying distinct populations of altered ‘specialized’ ribosomes. We show by comparative protein synthesis assays that different heterologous mRNA reporters based on luciferase are preferentially translated by distinct populations of specialized ribosomes. These mRNAs include reporters carrying premature termination codons (PTC) thus allowing us to identify specialized ribosomes that alter the efficiency of translation termination leading to enhanced synthesis of the wild-type protein. This finding suggests that these strains can be used to identify novel therapeutic targets in the ribosome. To explore this further we examined the translation of the mRNA encoding the extracellular matrix protein laminin β3 (LAMB3) since a LAMB3-PTC mutant is implicated in the blistering skin disease Epidermolysis bullosa (EB). This screen identified specialized ribosomes with reduced levels of RP L35B as showing enhanced synthesis of full-length LAMB3 in cells expressing the LAMB3-PTC mutant. Importantly, the RP L35B sub-population of specialized ribosomes leave both translation of a reporter luciferase carrying a different PTC and bulk mRNA translation largely unaltered.     

稻虱跗煽的个体发生研究：卵的形成和胚胎发育

捻翅目昆虫是胎生的,胚胎发育和孵化均在母体血腔内进行。稻虱跗蝇Elenchinus japonicus属捻翅目,跗煽科,寄生于白背稻虱、褐稻虱和灰稻虱。本文报道稻虱跗煽卵的形成各阶段：1)雌虫体内无典型的卵巢,所有卵在母体体腔内同步发育和成熟。最早发现的原卵是包囊干细胞,在雌幼虫血腔内。2)每个包囊细胞内含256个姐妹细胞,其中有一个细胞分化成卵母细胞,其余的成为营养细胞。3)成熟卵为椭圆形,大小为95-100X40-50μm。其胚胎发育过程按顺序包括：卵裂、胎盘形成、胚带分节、附肢形成和胚胎背合等阶段。稻虱跗蛔行单胚生殖。     

Analysis of the Contents of Oil Cells in Tasmannia lanceolata(Poir.) A. C. Smith (Winteraceae)

The simple, robust oil cells found in leaves of Tasmannia lanceolata(Poir.)A. C. Smith (Winteraceae) are shown to contain a preponderanceof the bioactive compound polygodial using both direct samplingand GCMS analysis of cell contents and Fourier Transform infraredspectroscopy. The implications of this for comparison of plantmaterial on the basis of extracts and essential oils are discussed.Copyright 2000 Annals of Botany Company Tasmannia lanceolata, Winteraceae, polygodial, direct sampling, FTIR spectrometry, oil cell, idioblast, antifeedant     

The Stigma of Dendrobium speciosum Sm. (Orchidaceae): A New Stigma Type Comprising Detached Cells Within a Mucilaginous Matrix

The stigma of Dendrobium speciosum does not correspond to anymorphological category previously described. The stigma lieson the lower surface of the column as an oval, bowl-shaped depressioncontaining a wet, jelly-like, viscid material, which comprisesa large number of elongated, detached cells suspended in a matrix.The stigmatic cells are thick walled and have a vacuolated cytoplasmcontaining amyloplasts. These cells give a positive reactionto fluorescein diacetate indicating that the plasma membraneis intact; this evidence points to the conclusion that the stigmaticcells are not detached, senescent or necrotic papillae. Histochemical staining of the matrix shows high levels of acidicpolysaccharides with low levels of lipids and proteins. Biochemicalanalysis shows this matrix to comprise around 80 per cent uronicacids. This highly specialized stigma may be a further evolutionarydevelopment of the wet papillate stigma resulting from the specialneeds of both pollination and the nutritional support of thelarge number of developing pollen tubes. Stigma, Dendrobium speciosum, Orchidaceae