Chapter 35 Plant Structure I Overview Plants are multicellular Contains organs which are made of different types of tissues which are made of different types of cells Monocot member of a clade consisting of flowering plants that have one embryonic seed leaf cotyledon Eudicot member of a clade that contains the vast majority of flowering plants that have two embryonic seed leaves cotyledons II Plant Structure A Organs 1 Ch 35 Plant Structure 1 Roots a Functions Anchors plants in soil Absorb minerals and water Stores organic nutrients b Types 1 Taproot system Develops from an embryonic root One main vertical root that has lateral branch roots Penetrates deep into the soil Good when ground water is not near surface Found in eudicots and gymnosperms Carrots 2 fibrous root system Found in monocots Embryonic root dies and does not form taproot Small roots emerge from stem Each small root form lateral roots Do not penetrate deeply into soil Excellent for preventing erosion Grass Short roots and water near surface 2 Ch 35 Plant Structure c Modifications Function Provide more support Store water and nutrients Absorb water and oxygen from air Type Prop roots Storage Aerial Buttress 3 Ch 35 Plant Structure 2 Stems make up shoot system a Functions Raises or separates leaves Raises reproductive structures Some plants stems are for food storage and asexual reproduction b c Structures 1 Nodes points where leaves attach 2 Internodes stem segments between nodes 3 Axillary bud bud that could eventually become a lateral shoot 4 Apical bud near the shoot tip where elongation occurs Modifications 1 stolons Asexual reproduction 2 bulbs 4 Ch 35 Plant Structure Vertical underground shoots 3 tubers Enlarged ends of rhizomes or stolons 4 rhizomes Horizontal shoot below surface 3 Leaves a Function Photosynthesis b Structures 5 Ch 35 Plant Structure Flattened blade Petiole Stalk of the leaf Joins leaf to a node c Types 1 By shape a Simple Single undivided blade Monocot b Compound Blade has multiple leaflets Eudicot c Double compound Each leaflet divided into smaller leaflets 2 By Veination a Parallel Monocot 6 Ch 35 Plant Structure d b Palmate Eudicot c Pinnate Eudicot Modifications Function Support Protection Storage Reproduction Types 7 Ch 35 Plant Structure Tendrils support Spines protection Bracts bright color attracts pollinators Reproductive leaves fall off and take root in the soil B Tissues 1 Dermal Tissue Outer protective covering a Function Protection against physical damage and pathogens and to regulate movement b Types 1 Epidermis Layer of tightly packed cells In leaves and stems epidermis covered by the cuticle a waxy coating 2 Periderm Replaces epidermis in woody plants during secondary growth 2 Vascular Tissue a Function Transport Long distance transport of materials between roots and shoot systems Provide support 8 Ch 35 Plant Structure b Types 1 Xylem Carries water and dissolved minerals up from roots to shoots 2 Phloem Carries organic nutrients from where they are made to where they are needed 3 Ground Tissue a Function b Types Storage Photosynthesis Support 1 Pith Inside middle of plant internal to vascular bundle 2 Cortex External to vascular tissue between vascular and dermal 9 Ch 35 Plant Structure C Cells common types 1 2 3 Parenchyma typical plant cells where photosynthesis occurs Thinned walled large vacuoles that function for photosynthesis support storage lateral transport Collenchyma flexible support for developing young plant shoots without restraining growth Located near surface of stem and leaf petioles Sclerenchyma rigid support for the plant occur in areas of plant that has stopped growing in length Provide support to mature structures 4 Xylem cells conduct water in tubular structures called tracheids and vessel elements Both are thin walled Tracheids are long and narrow Vessel elements are shorter and wider 5 Phloem cells transport sugars through long narrow tubes sieve cells 10 Ch 35 Plant Structure II Plant Growth A General Terminology 1 Determinate Growth growth stops after a certain period of time Most animals 2 Indeterminate Growth growth continues throughout life Plants a Meristems 1 Two Types of Meristems a Apical meristems Located in root tips and on buds of shoots Responsible for elongation primary growth Shoots grow closer to light and roots extend into ground b Lateral meristems Responsible for thickening Growth in circumference Occurs in woody plants Secondary Growth 1 Vascular cambium Adds tissue called secondary xylem wood and secondary phloem 2 Cork cambium Adds the bark to the outside Very thick and tough Does this by replacing epidermis with periderm 11 Ch 35 Plant Structure B Types of Growth 1 Primary Growth a Roots Root tips contain apical meristems Root has a root cap to protect the apical meristems as root pushes through the soil Growth occurs right behind root cap in three zones 1 Three Zones of Growth a Zone of Cell Division Where mitosis occurs Includes the apical meristems b Zone of Elongation Where most growth occurs c Zone of Differentiation Cells become distinct cell types 12 Ch 35 Plant Structure 2 Purpose Make all 3 types of tissues Primary 13 Ch 35 Plant Structure Dermal Vascular Ground b Shoots No cap on apicle meristem Apical meristem is a dome shaped mass of dividing cells at the tip of terminal bud Has consequences for organization of tissues in the stems 14 Ch 35 Plant Structure Stems Eudicot Monocot Embryo inside the seed has 2 seed leaves Embryo inside the seed has 1 leaf Vascular bundles in a ring Vascular bundles are random 15 Ch 35 Plant Structure c Leaves Tissue is organized so that all ground tissue is between the upper and lower epidermis 1 Mesophyll cells Ground tissues made of mesophyll cells parenchyma Contains chloroplast Palisade upper and Spengey lower 2 Vascular tissue Xylem and Phloem packaged into veins which also acts as a skeleton 3 Stomata Consists of a stomatal pore flanked by ground cells Used for oxygen and carbon dioxide exchange Water can be lost due to transpiration 2 Secondary Growth Thickening by lateral meristems Responsible for thickening in woody plants increases circumference Occurs in stems and roots rarely in leaves Mainly in gymnosperm species and eudicots rare in monocots a Vascular cambium Cylinder of cells that are one cell thick Able to divide Dividing cells are called initials Initials add secondary xylem to the inside and secondary phloem to the outside growth results in tree rings b Cork cambium