Section #2 Plant Structure and Anatomy

Transcription

1 Section #2 Plant Structure and Anatomy Most plants that people deal with daily are in the subdivision angiospermae Angiospermae plant that produces seed that are enclosed in a fruit Angiospermae is divided into two classes o Dicotyledonae 2 embryonic seed leaves (includes legumes) o Monocotyledonae 1 embryonic leaf (includes grasses) Plants are divided into three basic parts 1. Roots 2. Stems 3. Leaves Hierarchy of Human Structure Cells tissues organs Organ systems Human body Hierarchy of Plant Structure Cells tissues organs Plant A plant is an organ system Roots Stems Leaves

2 Roots Functions 1. anchoring the plant 2. absorb water and minerals from soil and transporting them 3. storing food produced by above ground portion of plant 4. propagation of new growth (tubers bulbs, rhizomes) Parts of a root system primary root originates from the embryo (main stem) secondary roots (fibrous)- branches of primary root root hairs specialized cell extensions that enter spaces between soil particles Dicotyledonae root system large primary root with fine branching laterals fineness increases with each branching order primary or secondary may swell (carrot, radish) Monocotyledonae root system often called fibrous root system lack ability to thicken has two phases 1. seminal roots (seed roots) o emerge from first node of seed embryo 2. adventitious roots (nodal or coronal) o emerge from basal nodes of grasses just below soil surface o become dominant root system for monocots Functions Stems

3 1. above ground structural component 2. attachment for leaves, flowers and fruit 3. water and food distribution (vascular system) Stem develops from bud to bear leaves contain nodes point where leaf is attached (# leaves = # of nodes) contain internodes spaces between nodes, point of growth for plants (internode elongation) Leaves Function 1. conduct photosynthesis 2. intercept light 3. gaseous exchange 4. cool plant Parts blade broad thin part of leaf petiole attaches blade to stem (some plants have no apparent petiole) stipules leaf like appendages at bases or petioles (not on all leaves) Arrangement of veins parallel netted venation Anatomy of Plants

4 The Cell = basics structural unit and physiological unit of crop plants, where chemical reactions of life occur providing metabolites for plant life and for human use. Two types of cells exist: 1. Prokaryotes Cells without nucleus Have genetic material not enclosed by membrane Examples bacteria and cyanophytes no internal organelles 2. Eukaryotes Cells with nucleus (genetic material surrounded by membrane) Found in humans, plants animals, algae and protozoa Cellular and nuclear membrane Plants differ having o Cell wall o Large vacuoles o Chloroplasts Eukaryotes 90% fluid ie. Cytoplasm o free amino acids o proteins o gluclose Structures of the Cell Cell walls Plasma membrane Non living Surrounds the protoplast Extend during cell enlargement Thickens during maturation Can maintain 70 psi Gives plant turgor Secondary cell walls made of cellulose, lignin

5 Regulates flow of dissolved substances and water in and out of the cell Contains lipid bilayer hydrophilic (water loving) facing outward hydrophobic (fat loving) facing inward Contains proteins embedded in lipid bylayer Regulate flow in and out of cells Cytoplasm Liquid matrix Suspends cytoplasmic organelles Water solutes and proteins Cellular Organelles Chloroplasts Double membrane plastids Contain chlorophyll Conducts Pn (autorophs) Have DNA (once separate organism???) Vacuole Occupies major volume of the cell Enables plant to separate from cytoplasm Contains sugars, water, salts Helps maintain turgidity of cell Mitochondria Site of aerobic respiration ie. Release of energy Allow plants to metabolize reduced carbon Converts stored food into ATP Nucleus Contain cellular DNA Governing body of cell Endoplasmic Reticulum (ER Site of protein synthesis Rough ER has ribosomes Transport for molecules with specific functions Ribosomes Protein synthesis Golgi Apparatus

6 Collects packages and delivers proteins made by ER Helps in creation of membranes (tonoplast surrounding vacuole) Peroxiomes Function in photoresiration Use oxygen to carry out catabolic reactions Types of Cells Found in Simple Tissues Parenchyma cells Most abundant and occur in all plant organs, thin cell walls, large vacuole, contain chloroplast if found in leaves, Collenchyma cells Thick cell walls, function as supporting tissue, flexible and living at maturity Sclerenchyma cells Thick rigid walls, heavily lignified, dead at maturity Tissues Tissues = large group of organized cells of similar structure to perform specific functions in the plant Two general types 1. meristematic 2. permanent Meristematic Contain actively dividing cells forming new tissues Found in 1. root tips 2. shoot tips 3. nodes 4. cambium parts Four types of meristematic tissues are 1. apical shoot or root (at apex or tip) add height or length can appear at axillary buds in leaf axils (can give rise to apical meristem if original is damaged)

7 produce buds, leaves, flowers and new root extensions in roots 2. lateral gives rise to thickening or increased girth located near outer edge stems and leaves form vascular cambium and give rise to new vascular tissue (xylem and phloem) cambium is responsible for bark production 3. intercalary found between two previously differentiated tissues found just above the nodes or base of leaves found in grasses between node and internode or between the leak blade and sheath increase length of stems and leaves in grasses Permanent Tissues generally do not become meristematic Simple permanent one type of structure Epidermis single layer found on exterior of stems, leaves flowers and fruits, usually have no pigment, protective covering, excrete waxy substance, allow for gaseous movement into plant Complex permanent conductive tissues (contain one or more simple cells) Xylem vertical transport of water and dissolved minerals and aerial support, water moves with transpiration stream due to differences in water potential, includes several types of cells tracheids, fibers and parenchyma cells Phloem- movement any direction of OM like carbohydrates and amino acids, contains parenchyma and sclerenchyma fibers Anatomy of Primary Organs Roots Penetrate into soil due to cell divisions and elongation Root tip protected by root cap Root hairs found just behind region of elongation Small projections of epidermal cells Increase total surface area Stems Support provided by thick celled cells and turgor Water and mineral transported in xylem Food is transported in phloem Monocot vs dicot arrangement

8 Leaves Flat broad thin structure increasing surface area Can reduce light impact by adjusting angle, by thickening and reflective surface Contain stomata, controlled by guard cells Two layers of cells palisade (thick) and spongy (loose) Pn occurs in palisade cells