DOCSLIB.ORG

Signals That Control Plant Vascular Cell Differentiation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Signals That Control Plant Vascular Cell Differentiation REVIEWS SIGNALS THAT CONTROL PLANT VASCULAR CELL DIFFERENTIATION Hiroo Fukuda Plant vascular cells originate from procambial cells, which are vascular stem cells. Recent studies with Zinnia elegans cell culture and Arabidopsis thaliana mutants indicate that intercellular- signalling molecules such as auxin, cytokinin, brassinosteroids and xylogen regulate the maintenance or differentiation of procambial cells through distinct intracellular-signal transduction and gene-expression machineries. This intercellular- and intracellular-signalling system might be involved in determining the continuity and pattern formation of vascular tissues. PLANT CELL BIOLOGY VASCULAR CELLS The body plan of plants is controlled by a combination such as PROCAMBIUM and VASCULAR CAMBIUM.But MONO- Cells that form the plant of clonal fate and positional information that is pro- COTYLEDONOUS PLANTS and ferns, in which secondary vascular tissues, including vided by local signals, as is commonly seen in multicel- thickening growth does not occur, lack cambium. procambial cells, cambial cells, lular organisms. Recent advances in molecular genetics Individual species of vascular plants form distinct radial sieve elements, companion cells, fibre cells, xylem and phloem and genome biology have uncovered unique mecha- patterns of vascular bundles in each organ, which have parenchyma cells, and tracheary nisms of plant-body formation. Vascular cells are been categorized as collateral, bicollateral, amphivasal elements. formed under a well-defined plant-differentiation pro- or amphicribral patterns (FIG. 1a, b). gramme. Although vascular cells usually differentiate at Procambial cells are vascular stem cells that are APICAL MERISTEM predicted positions and at a predicted time to form a derived from the apical meristem and give rise to xylem The meristematic tissue that is located at the tip of the shoot specific vascular pattern, the arrangement of the vascular and phloem precursor cells. The final step in vascular and root. It is composed of stem network can be altered by local signals or in response to development is the specification into distinct types of cells, which allow plants to environmental stimuli. This indicates the involvement vascular cells from the precursor cells. Phloem precur- continue to grow in height. of a non-clonal and flexible mechanism in vascular-pat- sor cells differentiate into various phloem cells such as SIEVE ELEMENTS SIEVE TUBES XYLEM tern formation. (which are components of ), The tissue that is responsible for VASCULAR CELLS are produced continuously from the COMPANION CELLS,phloem PARENCHYMA cells and phloem transporting water and APICAL MERISTEMS of shoots and roots in adult plants (FIG. 1). fibres. Xylem precursor cells give rise to TRACHEARY minerals. It also gives strength to In this situation, local cell–cell communication between ELEMENTS (TEs), xylem parenchyma cells and xylem the stem. developing vascular cells and cells that are not destined fibres, which together form xylem. TEs are components PHLOEM to differentiate into vascular cells might have a pivotal of a vessel — or tracheid — and at maturity, they are The tissue that is responsible for role in determining vascular cell differentiation. On the emptied by the loss of all cell contents, including the transporting the carbohydrates other hand, long-distance signalling also seems to be nucleus, to form hollow tubes through which fluids that are produced in leaves. necessary for the continuous production of vascular move. Therefore, cell death of TEs is programmed strands. developmentally. TEs possess a characteristic secondary Department of Biological Vascular strands connect plant organs that are often cell wall of annular, spiral, reticulate or pitted wall thick- Sciences, Graduate School separated by many metres, and provide a pathway for enings, which add strength and rigidity to the wall and of Science, The University the transport of signalling molecules as well as water prevent TEs from collapse under the high pressure that of Tokyo, 7-3-1 Hongo, and nutrients. For such vascular function, their conti- is exerted on fluid uptake. Tokyo 113-0033, Japan. nuity is a prerequisite.Vascular strands — which are Molecular-genetic studies with Arabidopsis thaliana e-mail: [email protected]. u-tokyo.ac.jp also referred to as vascular bundles — are composed of mutants and cellular studies with Zinnia elegans xylo- doi:10.1038/nrm1364 three tissues: XYLEM, PHLOEM and meristematic tissues genic cultures (BOX 1) have revealed the integrated NATURE REVIEWS | MOLECULAR CELL BIOLOGY VOLUME 5 | MAY 2004 | 379 © 2004 Nature Publishing Group REVIEWS Xylem a TE parenchyma c PROCAMBIUM A primary meristem that is derived from the apical Ph Pr Xy meristem and which gives rise to b primary vascular tissues and vascular cambium. Ph Xy VASCULAR CAMBIUM A lateral meristem that gives rise Collateral Bicollateral Amphicribral Amphivasal to secondary vascular tissues — d secondary xylem on the inner side and secondary phloem on the outer side in stems and roots, which results in an increase in the diameter of those organs. MONOCOTYLEDONOUS PLANTS A class of angiospermous plants that is characterized by the production of seeds with one cotyledon, such as rice, maize and wheat. SIEVE ELEMENT The components of sieve tubes that are separated from each Figure 1 | Vascular-pattern formation. a | The vascular system is composed of phloem (green, Ph), procambium (and/or vascular other by sieve plates. In contrast cambium; yellow, Pr) and xylem (Xy) that contains tracheary elements (grey) and xylem parenchyma cells (red), which make a distinct to tracheary elements, which are radial pattern of vascular bundles depending on the organ and plant species. Reproduced with permission from © (1982) depleted of all cell contents, sieve REF.120 elements contain a nucleus even John Wiley & Sons Inc. b | Four distinct radial patterns of phloem and xylem (red) within vascular bundles. c | The procambium, after maturation. stained blue to show the promoter activity of the HD-ZIP-III homeobox gene AtHB8, is formed as continuous columns of cells in embryos. In seedlings, the shoot and root meristems produce procambial cells to keep the continuity of vascular bundles. SIEVE TUBE Reproduced with permission from REF.119 © (2000) Shujyunsha Co. Ltd. d | van3 mutants have a fragmented vascular network 14 A series of sieve elements that in a cotyledon (right) compared with that in a wild-type cotyledon (left) . Reproduced with permission from REF.14 © (2000) form a long cellular tube The Company of Biologists Ltd. that functions in the transport of photosynthetic products. COMPANION CELLS Cells that are associated with nature of plant vascular formation, including the and controlling factor in the regeneration of vascular sieve elements and support integrity of the vascular system, intravascular-radial- strands around a wound. These studies also showed that them. An asymmetrical 1,2 cell division of a precursor cell pattern formation and vascular cell specification . polar auxin flow is needed for continuous vascular- produces a sieve element and a Here,I review recent findings on plant vascular cell dif- pattern formation. Indeed, the prevention of polar companion cell. ferentiation, with a special emphasis on intercellular and auxin transport by specific inhibitors causes the forma- intracellular signalling. Because little is known about the tion of local aggregates of vascular cells and discontinu- PARENCHYMA molecular mechanism of phloem cell differentiation, ous veins in newly developed leaves6,7.By contrast, such A tissue that is composed of cells that have thin cell walls and has a vascular cell differentiation is described mainly with inhibitors were less effective at inhibiting vascular differ- relatively flexible ability to regard to xylem cell differentiation. In appropriate cases, entiation from the procambium, patterns of which had differentiate. A. thaliana and Z. elegans genes and proteins are distin- already formed in embryonic cotyledons. So, these guished by the prefixes At and Ze, respectively. inhibitors seem to affect vascular development through TRACHEARY ELEMENT The thick-walled cylindrical cell disruptions in the development of procambial patterns. 4,5 that is a component of vessels, or Intercellular signals and vascular continuity Sachs proposed the ‘auxin-flow canalization hypothe- tracheids, which are water- A role for auxin flow. Pioneering studies by Jacobs3 and sis’,which suggests that auxin flow, starting initially by conducting tissues. Sachs4,5 showed that indoleacetic acid (IAA) — a nat- diffusion, induces the formation of the polar-auxin- ural auxin that is produced in the apical region of transport-cell system.This, in turn, promotes auxin BASIPETALLY Toward the root tip from the shoots (including the apical meristem and expanding transport, leading to canalization of the auxin flow shoot tip. leaves) and transported BASIPETALLY — was the limiting along a narrow column of cells (FIG. 2).This continuous 380 | MAY 2004 | VOLUME 5 www.nature.com/reviews/molcellbio © 2004 Nature Publishing Group REVIEWS Box 1 | Xylem cell differentiation induced in vitro without cell division Single mesophyll cells (see figure part a,left panel) can be a isolated mechanically from expanding leaves of Zinnia elegans.When the isolated mesophyll cells are cultured in vitro in the presence of auxin and cytokinin, they transdifferentiate synchronously within 72 hours, and at a high frequency, into tracheary
Load more

Recommended publications
  • EVIDENCE for AUXIN REGULATION of BORDERED-PIT POSITIONING DURING TRACHEID DIFFERENTIATION in LARIX LARICINA By
    IAWA Journal, Vol. 16 (3),1995: 289-297 EVIDENCE FOR AUXIN REGULATION OF BORDERED-PIT POSITIONING DURING TRACHEID DIFFERENTIATION IN LARIX LARICINA by Mathew Adam Leitch & Rodney Arthur Savidge 1 Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, New Brunswick, E3B 6C2, Canada SUMMARY Chips containing cambium intact between xylem and phloem were cut from 8-year-old stem regions of 20-30-year-old dormant Larix laricina in late spring and cultured under controlled conditions for six weeks on a defined medium containing varied concentrations of I-naphthalene acetic acid (NAA, a synthetic auxin). Microscopy revealed that auxin was essential for cambial growth and tracheid differentiation. Low (0.1 mg/l) and high (10.0 mg/l) auxin concentrations were conducive to bordered pits forming in tangential walls, whereas an intermediate concentration (1.0 mg/l) of NAA favoured positioning of pits in radial walls. INTRODUCTION Two decades ago, Barnett and Harris (1975) pointed out that the processes involved in bordered-pit formation were incompletely understood, in particular the way in which the pit site is determined and how adjoining cells form a perfectly symmetrical bor­ dered-pit pair. Observing that radial walls of enlarging cambial derivatives were vari­ ably thick and thin, Barnett and Harris (1975) advanced the hypothesis that bordered­ pit development occurs at sites where the primary wall is thinned through the process of centrifugal displacement of microfibrils. Others, however, considered that a thick­ ening rather than a thinning of the primary wall was indicative of the site where pit development commenced (FengeI1972; Parham & Baird 1973).
    [Show full text]
  • Introduction to the Cell Cell History Cell Structures and Functions
    Introduction to the cell cell history cell structures and functions CK-12 Foundation December 16, 2009 CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based collaborative model termed the “FlexBook,” CK-12 intends to pioneer the generation and distribution of high quality educational content that will serve both as core text as well as provide an adaptive environment for learning. Copyright ©2009 CK-12 Foundation This work is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA. Contents 1 Cell structure and function dec 16 5 1.1 Lesson 3.1: Introduction to Cells .................................. 5 3 www.ck12.org www.ck12.org 4 Chapter 1 Cell structure and function dec 16 1.1 Lesson 3.1: Introduction to Cells Lesson Objectives • Identify the scientists that first observed cells. • Outline the importance of microscopes in the discovery of cells. • Summarize what the cell theory proposes. • Identify the limitations on cell size. • Identify the four parts common to all cells. • Compare prokaryotic and eukaryotic cells. Introduction Knowing the make up of cells and how cells work is necessary to all of the biological sciences. Learning about the similarities and differences between cell types is particularly important to the fields of cell biology and molecular biology.
    [Show full text]
  • How Trees Modify Wood Development to Cope with Drought
    DOI: 10.1002/ppp3.29 REVIEW Wood and water: How trees modify wood development to cope with drought F. Daniela Rodriguez‐Zaccaro | Andrew Groover US Forest Service, Pacific Southwest Research Station; Department of Plant Societal Impact Statement Biology, University of California Davis, Drought plays a conspicuous role in forest mortality, and is expected to become more Davis, California, USA severe in future climate scenarios. Recent surges in drought-associated forest tree Correspondence mortality have been documented worldwide. For example, recent droughts in Andrew Groover, US Forest Service, Pacific Southwest Research Station; Department of California and Texas killed approximately 129 million and 300 million trees, respec- Plant Biology, University of California Davis, tively. Drought has also induced acute pine tree mortality across east-central China, Davis, CA, USA. Email: [email protected], agroover@ and across extensive areas in southwest China. Understanding the biological pro- ucdavis.edu cesses that enable trees to modify wood development to mitigate the adverse effects Funding information of drought will be crucial for the development of successful strategies for future for- USDA AFRI, Grant/Award Number: 2015- est management and conservation. 67013-22891; National Science Foundation, Grant/Award Number: 1650042; DOE Summary Office of Science, Office of Biological and Drought is a recurrent stress to forests, causing periodic forest mortality with enor- Environmental Research, Grant/Award Number: DE-SC0007183 mous economic and environmental costs. Wood is the water-conducting tissue of tree stems, and trees modify wood development to create anatomical features and hydraulic properties that can mitigate drought stress. This modification of wood de- velopment can be seen in tree rings where not only the amount of wood but also the morphology of the water-conducting cells are modified in response to environmental conditions.
    [Show full text]
  • The Structure, Function, and Biosynthesis of Plant Cell Wall Pectic Polysaccharides
    Carbohydrate Research 344 (2009) 1879–1900 Contents lists available at ScienceDirect Carbohydrate Research journal homepage: www.elsevier.com/locate/carres The structure, function, and biosynthesis of plant cell wall pectic polysaccharides Kerry Hosmer Caffall a, Debra Mohnen a,b,* a University of Georgia, Department of Biochemistry and Molecular Biology and Complex Carbohydrate Research Center, 315 Riverbend Road Athens, GA 30602, United States b DOE BioEnergy Science Center (BESC), 315 Riverbend Road Athens, GA 30602, United States article info abstract Article history: Plant cell walls consist of carbohydrate, protein, and aromatic compounds and are essential to the proper Received 18 November 2008 growth and development of plants. The carbohydrate components make up 90% of the primary wall, Received in revised form 4 May 2009 and are critical to wall function. There is a diversity of polysaccharides that make up the wall and that Accepted 6 May 2009 are classified as one of three types: cellulose, hemicellulose, or pectin. The pectins, which are most abun- Available online 2 June 2009 dant in the plant primary cell walls and the middle lamellae, are a class of molecules defined by the pres- ence of galacturonic acid. The pectic polysaccharides include the galacturonans (homogalacturonan, Keywords: substituted galacturonans, and RG-II) and rhamnogalacturonan-I. Galacturonans have a backbone that Cell wall polysaccharides consists of -1,4-linked galacturonic acid. The identification of glycosyltransferases involved in pectin Galacturonan a Glycosyltransferases synthesis is essential to the study of cell wall function in plant growth and development and for maxi- Homogalacturonan mizing the value and use of plant polysaccharides in industry and human health.
    [Show full text]
  • Plant:Animal Cell Comparison
    Comparing Plant And Animal Cells http://khanacademy.org/video?v=Hmwvj9X4GNY Plant Cells shape - most plant cells are squarish or rectangular in shape. amyloplast (starch storage organelle)- an organelle in some plant cells that stores starch. Amyloplasts are found in starchy plants like tubers and fruits. cell membrane - the thin layer of protein and fat that surrounds the cell, but is inside the cell wall. The cell membrane is semipermeable, allowing some substances to pass into the cell and blocking others. cell wall - a thick, rigid membrane that surrounds a plant cell. This layer of cellulose fiber gives the cell most of its support and structure. The cell wall also bonds with other cell walls to form the structure of the plant. chloroplast - an elongated or disc-shaped organelle containing chlorophyll. Photosynthesis (in which energy from sunlight is converted into chemical energy - food) takes place in the chloroplasts. chlorophyll - chlorophyll is a molecule that can use light energy from sunlight to turn water and carbon dioxide gas into glucose and oxygen (i.e. photosynthesis). Chlorophyll is green. cytoplasm - the jellylike material outside the cell nucleus in which the organelles are located. Golgi body - (or the golgi apparatus or golgi complex) a flattened, layered, sac-like organelle that looks like a stack of pancakes and is located near the nucleus. The golgi body modifies, processes and packages proteins, lipids and carbohydrates into membrane-bound vesicles for "export" from the cell. lysosome - vesicles containing digestive enzymes. Where the digestion of cell nutrients takes place. mitochondrion - spherical to rod-shaped organelles with a double membrane.
    [Show full text]
  • A Physiologically Explicit Morphospace for Tracheid-Based Water Transport in Modern and Extinct Seed Plants
    A Physiologically Explicit Morphospace for Tracheid-based Water Transport in Modern and Extinct Seed Plants The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Wilson, Jonathan P., and Andrew H. Knoll. 2010. A physiologically explicit morphospace for tracheid-based water transport in modern and extinct seed plants. Paleobiology 36(2): 335-355. Published Version doi:10.1666/08071.1 Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:4795216 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#OAP Wilson - 1 A Physiologically Explicit Morphospace for Tracheid-Based Water Transport in Modern and Extinct Seed Plants Jonathan P. Wilson* Andrew H. Knoll September 7, 2009 RRH: PHYSIOLOGICALLY EXPLICIT MORPHOSPACE LRH: JONATHAN P. WILSON AND ANDREW H. KNOLL Wilson - 2 Abstract We present a morphometric analysis of water transport cells within a physiologically explicit three-dimensional space. Previous work has shown that cell length, diameter, and pit resistance govern the hydraulic resistance of individual conducting cells; thus, we use these three parameters as axes for our morphospace. We compare living and extinct plants within this space to investigate how patterns of plant conductivity have changed over evolutionary time. Extinct coniferophytes fall within the range of living conifers, despite differences in tracheid-level anatomy. Living cycads, Ginkgo biloba, the Miocene fossil Ginkgo beckii, and extinct cycadeoids overlap with both conifers and vesselless angiosperms.
    [Show full text]
  • University of Michigan University Library
    CONTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY THE UNIVERSITY OF MICHIGAN VOL. XIX, NO.6, pp. 65-88 (7 pls., 1 fig.) SEFTEMBER25, 1964 A FOSSIL DENNSTAEDTIOID FERN FROM THE EOCENE CLARNO FORMATION OF OREGON BY CHESTER A. ARNOLD and LYMAN H. DAUGHERTY MUSEUM OF PALEONTOLOGY THE UNIVERSITY OF MICHIGAN ANN ARBOR CONTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY Director: LEWISB. KELLUM The series of contributions from the Museum of Paleontology is a medium for the publication of papers based chiefly upon the collections in the Museum. When the number of pages issued is sufficient to make a volume, a title page and a table of contents will be sent to libraries on the mailing list, and to individuals upon request. A list of the separate papers may also be obtained. Correspondence should be directed to the Museum of Paleontology, The University of Michigan, Ann Arbor, Michigan. VOLUMEXIX 1. Silicified Trilobites from the Devonian Jeffersonville Limestone at the Falls of the Ohio, by Erwin C. Stumm. Pages 1-14, with 3 plates. 2. Two Gastropods from the Lower Cretaceous (Albian) of Coahuila, Mexico, by Lewis B. Kellum and Kenneth E. Appelt. Pages 15-22, with 2 figures. 3. Corals of the Traverse Group of Michigan, Part XII, The Small-celled Species of Favosites and Emmonsia, by Erwin C. Stumm and John H. Tyler. Pages 23-36, with 7 plates. 4. Redescription of Syntypes of the Bryozoan Species Rhombotrypa quadrata (Rominger), by Roger J. Cuffey and T. G. Perry. Pages 37-45, with 2 plates. 5. Rare Crustaceans from the Upper Devonian Chagrin Shale in Northern Ohio, by Myron T.
    [Show full text]
  • Chloroplasts Are the Food Producers of the Cell. the Organelles Are Only Found in Plant Cells and Some Protists Such As Algae
    Name: ___________________________ Cell #2 H.W. due September 22nd, 2016 Period: _________ Chloroplasts are the food producers of the cell. The organelles are only found in plant cells and some protists such as algae. Animal cells do not have chloroplasts. Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells. It is like a solar panel that changes sunlight energy into electric energy. The entire process is called photosynthesis and it all depends on the little green chlorophyll molecules in each chloroplast. In the process of photosynthesis, plants create sugars and release oxygen (O2). The oxygen released by the chloroplasts is the same oxygen you breathe every day. Chloroplasts are found in plant cells, but not in animal cells. The purpose of the chloroplast is to make sugars that feed the cell’s machinery. Photosynthesis is the process of a plant taking energy from the Sun and creating sugars. When the energy from the Sun hits a chloroplast and the chlorophyll molecules, light energy is converted into the chemical energy. Plants use water, carbon dioxide, and sunlight to make sugar and oxygen. During photosynthesis radiant energy or solar energy or light energy is transferred into chemical energy in the form of sugar (glucose). You already know that during photosynthesis plants make their own food. The food that the plant makes is in the form of sugar that is used to provide energy for the plant. The extra sugar that the plant does not use is stored as starch for later use. Mitochondria are known as the powerhouses of the cell.
    [Show full text]
  • + Complex Tissues
    + Complex Tissues ! Complex tissues are made up of two or more cell types. ! Xylem - Chief conducting tissue for water and minerals absorbed by the roots. ! Vessels - Made of vessel elements. ! Long tubes open at each end. ! Tracheids - Tapered at the ends with pits that allow water passage between cells. ! Rays - Lateral conduction. + Complex Tissues - Xylem ! Tracheids ! Long, thin cells with pointed ends that conduct water vertically ! Line up in columns like pipes by overlapping their tapered ends ! die when reach maturity ! Water conducted through tubes made up of tracheid cell walls ! Wherever two ends join, small holes in the cell wall called pits line up to allow water to flow from one tracheid to another. + Complex Tissues - Xylem ! Pits always occur in pairs so that a pair of pits lines up on either side of the middle lamella, or center layer, of the cell wall. + Complex Tissues - Xylem !Vessel elements !barrel-shaped cells with open ends that conduct water vertically. !line up end to end forming columns, called vessels, that conduct water. !Some have completely open ends, while others have narrow strips of cell wall material that partially covers the ends !Die at maturity, like tracheids. + Complex Tissues - Xylem ! Ray cells………. ! Long lived parenchyma cells that extend laterally like the spokes of a wheel from the center of a woody stem out towards the exterior of the stem ! alive at maturity ! Transport materials horizontally from center outward + Complex Tissues - Xylem ! Xylem fibers – ! long, thin sclerenchyma cells ! Xylem parenchyma cells- that run parallel to the ! Living cells vessel element ! Distributed among tracheids and vessels ! Help strengthen and support xylem ! Store water and nutrients + Complex Tissues - Phloem ! Phloem brings sugar [glucose from photosynthesis] from the leaves to all parts of the plant body.
    [Show full text]
  • Transition Dates from Earlywood to Latewood and Early Phloem to Late Phloem in Norway Spruce
    Article Transition Dates from Earlywood to Latewood and Early Phloem to Late Phloem in Norway Spruce Jožica Griˇcar 1,* , Katarina Cufarˇ 2 , Klemen Eler 3,4 , Vladimír Gryc 5, Hanuš Vavrˇcík 5 , Martin de Luis 6 and Peter Prislan 7 1 Department of Forest Yield and Silviculture, Slovenian Forestry Institute, 1000 Ljubljana, Slovenia 2 Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; [email protected] 3 Department of Agronomy, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; [email protected] 4 Department of Forest Ecology, Slovenian Forestry Institute, 1000 Ljubljana, Slovenia 5 Department of Wood Science and Technology, Faculty of Forestry and Wood Technology, Mendel University in Brno, 61300 Brno, Czech Republic; [email protected] (V.G.); [email protected] (H.V.) 6 Department Geografía y O.T., University of Zaragoza, 50009 Zaragoza, Spain; [email protected] 7 Department of Forest Techniques and Economy, Slovenian Forestry Institute, 1000 Ljubljana, Slovenia; [email protected] * Correspondence: [email protected] Abstract: Climate change will affect radial growth patterns of trees, which will result in different forest productivity, wood properties, and timber quality. While many studies have been published on xylem phenology and anatomy lately, little is known about the phenology of earlywood and latewood formation, also in relation to cambial phenology. Even less information is available for Citation: Griˇcar, J.; Cufar,ˇ K.; Eler, K.; phloem. Here, we examined year-to-year variability of the transition dates from earlywood to Gryc, V.; Vavrˇcík,H.; de Luis, M.; Prislan, P.
    [Show full text]
  • Plastid in Human Parasites
    SCIENTIFIC CORRESPONDENCE being otherwise homo­ Plastid in human geneous. The 35-kb genome-containing organ­ parasites elle identified here did not escape the attention of early Sm - The discovery in malarial and toxo­ electron microscopists who plasmodial parasites of genes normally - not expecting the pres­ occurring in the photosynthetic organelle ence of a plastid in a proto­ of plants and algae has prompted specula­ zoan parasite like tion that these protozoans might harbour Toxoplasma - ascribed to it a vestigial plastid1• The plastid-like para­ various names, including site genes occur on an extrachromosomal, 'Hohlzylinder' (hollow cylin­ maternally inherited2, 35-kilobase DNA der), 'Golgi adjunct' and circle with an architecture reminiscent of 'grof3e Tilkuole mit kriiftiger that of plastid genomes3•4• Although the Wandung' (large vacuole 35-kb genome is distinct from the 6-7-kb with stout surrounds) ( see linear mitochondrial genome3-6, it is not refs cited in ref. 9). Our pre­ known where in the parasite cells the plas­ liminary experiments with tid-like genome resides. Plasmodium falciparum, the To determine whether a plastid is pre­ causative agent of the most sent, we used high-resolution in situ lethal form of malaria, hybridization7 to localize transcripts of a identify an organelle (not plastid-like 16S ribosomal RNA gene shown) which appears sim­ from Toxoplasma gondii8, the causative ilar to the T. gondii plastid. agent of toxoplasmosis. Transcripts accu­ The number of surrounding mulate in a small, ovoid organelle located membranes in the P. anterior to the nucleus in the mid-region falciparum plastid, and its of the cell (a, b in the figure).
    [Show full text]
  • Lesson 1: Plant Cells
    LESSON 1: PLANT CELLS LEVEL 1 What is a plant? A quick answer might be “something that is green and has leaves.” But are all plants green? There’s a type of maple tree that has purplish-red leaves. Obviously it is a plant because it is a tree. So being green can’t be a requirement for being a plant, though most plants are indeed green. What about leaves? Do all plants have leaves? Think about a cactus. Do those sharp needles count as leaves? Or what about the “stone plant”? It looks like a rock. (No kidding--it really does!) What makes a plant a plant? The answer is... a plant is a plant because it can make its own food using a process called photosynthesis. Plants can use the energy from sunlight to turn water and carbon dioxide into sugar. (“Photo” means “light,” and “synthesis” means “make.”) Wouldn’t it be nice if you could make your own food from sunlight? No more going to the grocery store or planting a garden. You could just stand in the sunshine, take a deep breath, drink a glass of water, and make your own food. Sounds funny, but that’s exactly what plants do. They take water from the ground, carbon dioxide from the air, and energy from light and turn them into food. Photosynthesis is a very complicated chemical process. The exact details of how a plant takes apart the molecules of water and carbon dioxide and turns them into sugar is so complicated that you need a college degree in chemistry to really understand it.
    [Show full text]