Estructura 2023 PDF - Plant Cell and Tissue Architecture

FISIOLOGÍA VEGETAL ADRIANA SÁNCHEZ [email protected] Ext. 4034 • Presentación del programa – Guía de asignatura – Laboratorio – “Reglas” del curso – Preguntas • Introducción (Capítulo 1) Escalas moleculares a globales De las plantas más pequeñas a las más grandes Wolffia 1 milí...

FISIOLOGÍA VEGETAL ADRIANA SÁNCHEZ [email protected] Ext. 4034 • Presentación del programa – Guía de asignatura – Laboratorio – “Reglas” del curso – Preguntas • Introducción (Capítulo 1) Escalas moleculares a globales De las plantas más pequeñas a las más grandes Wolffia 1 milímetro de longitud Hyperion (redwood) Sequoia sempervirens 115.92 metros Qué es anatomía vegetal? • ANATOMIA: estudio de la estructura de los organismos… mirar células, tejidos (Morfología: Estudiar la forma) Qué es fisiología vegetal? • FISIOLOGIA: estudio de la función de las células, tejidos, órganos; y la física/bioquímica de esas funciones Why is it important to study plant architecture? Domestication and improvement have dramatically altered the form and height of many crops Broccoli Kale All these plants belong to the same species: Brassica oleracea Understanding the genetic basis and the physiological consequences of these changes could aid crop breeding! Kohlrabi Cauliflower Wild cabbage Brussels sprouts Cabbage Investigación Adriana PLANT AND CELL ARCHITECTURE CHAPTER 1 REVIEW TOPICS A. Cells B. Tissues C. Organs A. PLANT CELLS • Plant cells: “basic building blocks” • Can specialize in different forms and functions ALL CELLS HAVE…? Protective membrane Protoplasm – cell contents immersed in fluid Organelles – structures for cell function Control center and DNA Ribosomes Endoplasmatic reticulum Golgi apparatus Nucleus Mitochondria Chloroplast Peroxisomes Glyoxysomes Vacuole Cell wall Cell membrane A. PLANT CELLS • Endomembrane System (ES): Endoplasmatic reticulum, nuclear envelope, Golgi apparatus, vacuole, endosomes, plasma membrane • Independently dividing or fusing organelles derived from ES: oil bodies, peroxisomes, glyoxysomes • Independently dividing, semiautonomous: plastids, mitochondria Cytoplasm • Viscous fluid containing organelles • Components of cytoplasm – – – – Interconnected filaments & fibers Fluid = cytosol Organelles & nucleus Storage substances Endomembrane System (ES) 1. MEMBRANES NEXT CLASS! Plasma membrane • Encloses the cell content • Is a dynamic and intricate structure that regulates material transported across the membrane • It is selectively permeable (or semi-permeable): certain molecules can move through, and others cannot • Phospholipid bilayer and proteins • All cells have plasma membranes and many of their organelles also have membranes FLUID MOSAIC MODEL Phospholipids • Polar – Hydrophilic head – Hydrophobic tail Membranes are more fluid when they contain more unsaturated fatty acids within their phospholipids. More unsaturated fatty acids result in increased distance between the lipids making the layer more fluid. Temperature affects the fluidity of membranes. How? Proteins INTEGRAL: embedded. Serve as ion channels PERIPHERAL: membrane surface. Interacts with major elements of cytoskeleton (microtubules and microfilaments) ANCHORED: bound to the surface via lipid molecules Endomembrane System (ES) 2. NUCLEUS: Genetic information regulating metabolism, growth, cell differentiation – – – – Surrounded by nuclear envelope (double membr.) Nuclear pores Chromosomes + proteins = chromatin Nucleolus: site of ribosome synthesis Endomembrane System (ES) 3. ENDOPLASMIC RETICULUM (ER) • Network of interconnected membranes, continuous with nuclear envelope • Helps move substances within cells • Communication network between organelles • Synthesis and delivery system for proteins/lipids • Two types – Rough – Smooth Rough Endoplasmic Reticulum • Ribosomes attached to surface – Manufacture proteins – Not all ribosomes attached to rough ER • May modify proteins from ribosomes Smooth Endoplasmic Reticulum • No attached ribosomes • Has enzymes that help build molecules – Carbohydrates – Lipids Endomembrane System (ES) 4. GOLGI APPARATUS • Involved in synthesis of plant cell wall • Packaging & shipping station of cell • Secretion Endomembrane System (ES) 6. VACUOLES • Up to 95% of cell volume • Cell expansion • Membrane bound storage sacs • Contents – – – – Water Food Wastes 2ary metabolites Water+solutes TONOPLAST Independently dividing or fusing organelles 1. OIL BODIES: mostly for seed development. Monolayer. 2. PEROXISOMES & GLYOXYSOMES (mitochondria-oil bodies): monolayer. Associate with organelles. Specialized in the metabolism of fatty acids and glyoxylate; carrying out oxidative reactions using molecular oxygen PEROXISOME Independently dividing, semiautonomous Bacteria-like organelles: • Their own DNA and ribosomes • Double membranes • Divide independently of nuclear division • Types 1. MITOCHONDRIA: substrates? 2. CHLOROPLASTS: origin? PLANT CYTOSKELETON • Filamentous proteins • Made of 3 fiber types – Microfilaments (solid; actin) – Microtubules (hollow; tubulin) 3 functions: – mechanical support – anchor organelles – help move substances B. TISSUES Four Main Tissue Types in Plants 1- Meristematic Tissue: are responsible for plant growth 2- Dermal Tissue: the outermost cell layers of the plant 3- Vascular Tissue: the transportation “veins” of the plant (xylem and phloem) 4- Ground Tissue: basically everything else in the plant (cells used for structure or rigidity, photosynthesizing cells, Etc.) 28 Apical meristems lengthen roots and stems (primary growth) Lateral meristems increase root and stem width (secondary growth) Meristem Tissue Root tip Terminal bud Stem tip Axillary bud There are 4 places we find apical meristem tissue: Stems: Terminal buds, axillary buds Roots: Root tips, pericycle Roots can branch too! But wait… do they have axillary buds??!? Stem tip Roots do not have axillary buds to form lateral branches, like stems do. Instead, lateral roots elongate out of the pericycle. Lateral root emerging from pericycle Stem tip Root Cortex: Endodermis • Endodermis: the innermost layer of the cortex • The Casparian strip: a water-impermeable strip of waxy material found in the endodermis. Controls the uptake of minerals into the xylem Primary Growth Summary Stem tip Meristematic tissues are tissues that exhibit continuous growth, making stems and roots longer. There are also apical meristems on the tips of all roots under the root cap, and in the pericycle (those give rise to secondary roots). Secondary Growth refers to increasing girth as branches and roots get fatter over time, through laying down of new xylem and phloem by the vascular cambium, and new cork by the cork cambium. Secondary growth is found in most perennial* seed plants (including gymnosperms) with the exception of monocots. Old Xylem Younger Xylem Vascular cambium Phloem BARK Cork cambium Cork *perennial: living more than two years Procambium differentiates into: Primary xylem Vascular cambium Primary phloem Vascular cambium then divides, giving rise to: Secondary Xylem & Phloem Secondary Growth Label the vascular cambium, the youngest phloem, and the youngest xylem Note: 4-10x more xylem is produced compared to phloem Vascular tissue forms rings in trees • Annual rings: xylem formed by the vascular cambium during one growing season • One ring = one year (temperate zones) Secondary Growth Roots can get fatter too. BUT, once they begin accumulating 2o growth & bark, they are no longer absorptive. 39 Only first year roots can absorb water, because they still have their epidermal root hairs. Once the epidermis is shed, and cork accumulates, they are no longer absorptive and rely on mycorrhizae. In young (not bark-covered) roots, there is one outer dermal layer: epidermis Sclerenchyma fibers (purple) Phloem (blue) Vascular cambium Xylem (purple) Monocots do not have a vascular cambium, and therefore do not exhibit secondary growth in roots OR stems. 41 Four Main Tissue Types in Plants 1- Meristematic Tissue: are responsible for plant growth 2- Dermal Tissue: the outermost cell layers of the plant 3- Vascular Tissue: the transportation “veins” of the plant (xylem and phloem) 4- Ground Tissue: basically everything else in the plant (cells used for structure or rigidity, photosynthesizing cells, Etc.) Dermal Tissue The two types of dermal tissues are epidermis and periderm. Leaves, young stems, and young roots are covered by a single Stem tip layer of epidermal cells. As roots and stems get thicker, the epidermis falls off, and is replaced by tougher, dead “periderm” tissue (cork), produced by the cork cambium. Dermal tissue • Epidermis is the outermost layer of cells • Like the “skin” of animals (protection) • In stems and leaves, epidermis has cuticle, a waxy layer that prevents water loss. • Some have trichomes, hairs. • Root epidermis has root hairs, for water and nutrient absorption Leaf epidermis • Is transparent – so that sun light can go through. • Waxy cuticle protects against drying out • Lower epidermis: stomata with guard cells – for gas exchange (CO2, H2O in; O2 out) Cork Oak (Quercus suber): cork can be stripped, but cork cambium is left intact 46 Four Main Tissue Types in Plants 1- Meristematic Tissue: are responsible for plant growth 2- Dermal Tissue: the outermost cell layers of the plant 3- Vascular Tissue: the transportation “veins” of the plant (xylem and phloem) 4- Ground Tissue: basically everything else in the plant (cells used for structure or rigidity, photosynthesizing cells, Etc.) Xylem 47 Xylem cells are heavily lignified, dead (hollow) cells used to conduct water & minerals. Xylem cells are dead! They are hollow cells and consist only of cell wall ). Xylem 48 There are 2 types of xylem cells: - Tracheids (skinny): most ferns and gymnosperms. Water moves through pits. - Vessel elements (wide): Water moves via perforation plates. **Angiosperms (and Gnetophytes) conduct water via vessels AND tracheids 49 Tracheids Gymnosperm wood Vessels Tracheids Angiosperm wood Which conducts water faster: Vessels or Tracheids? 50 Conduit diameter (µm) Larger xylem diameter = faster conductivity of water, due to lower frictional restrictions to water flow Phloem Phloem is comprised of living cells called “sieve elements”, which conduct carbohydrates dissolved in water. Phloem mother cell 51 “Companion” cells load the carbohydrates into the phloem. The nucleus and ribosomes of the companion cell also control cell functions of the sieve element, since it has lost these organelles. CC SE Both cells begin as fully functioning. SE undergoes selective autophagy. During this process, the vacuole, ribosomes, Golgi bodies, cytoskeleton, and nucleus are degraded. The remaining organelles are held in place along the cell membrane by “microclamps” 52 53 Xylem flows upwards from the roots; phloem flows from source to sink tissues 54 Four Main Tissue Types in Plants 1- Meristematic Tissue: are responsible for plant growth 2- Epidermal Tissue: the outermost cell layers of the plant 3- Vascular Tissue: the transportation “veins” of the plant (xylem and phloem) 4- Ground Tissue: basically everything else in the plant (sclerenchyma, collenchyma, parenchyma). 3 Types of Ground Tissue d i g i R y r e V Sclerenchyma Fibers Sclereids Flexibly Rigid So ft Parenchyma Collenchyma Sclerenchyma are cells that are made of up to 90% lignified cell wall and die at maturity. They basically make tissues hard and inflexible 56 1. Fibers Fibers are frequently associated with vascular tissue– keep it from bending and breaking Fibers of monocots can be used to make rope and textiles 2. Sclereids Examples: lignified granules found in nut shells, seed coats and periderm (outer bark) Sclereids can also have an anti-herbivory function in leaves 3 Types of Ground Tissue d i g i R y r e V Sclerenchyma Fibers Sclereids Flexibly Rigid So ft Parenchyma Collenchyma - Flexibly rigid strands or cylinders; living cells - Unevenly thick primary walls, but no lignified secondary walls - Found in parts of the plant that are still growing. Collenchyma 3 Types of Ground Tissue d i g i R y r e V Sclerenchyma Fibers Sclereids Flexibly Rigid So ft Parenchyma Examples Collenchyma Starch-storing Fleshy Photosynthetic root cells fruit leaf cells Leaf Mesophyll • Middle of the leaf (meso-phyll) • Composed of photosynthetic ground cells: • Palisade parenchyma (long columns below epidermis; have lots chloroplasts for photosynthesis) Spongy parenchyma (spherical cells) with air spaces around (for gas exchange) Amyloplasts 62 Amyloplasts are plastids that store starch in starch-storage parenchyma Estructura y soporte Almacenaje, fotosíntesis Soporte y estructura Collenchyma is living (has a nucleus); sclerenchyma is dead. Also notice that a large % of the cell space of sclerenchyma is filled with secondary cell wall, relative to collenchyma. Lastly, sclerenchyma contains lignin, collenchyma does not (so it’s less rigid). Parenchyma: living cells surrounded by a thin cell wall C. ORGANS Tissues that act together to serve a specific function • Roots Dermal Vascular Ground ROOTS: Anchorage, water/nutrient absorption from soil, storage (surplus sugars, starch), water/nutrient transport • Stems Dermal Vascular Ground STEMS: Support, water/nutrient transport • Leaves Dermal Vascular Ground LEAVES: Photosynthesis (food production)