March 28, 2005 Plant Tissues Chapter 26 Jin Hoe Huh

Angiosperms – flowering plants The angiosperms are seed-bearing vascular plants In terms of distribution and diversity, they are the most successful plants on Earth The structure and function of this plant group help explain its success

Flowering Plant Life Cycle Diploid Double fertilization Meiosis Meiosis Haploid Mitosis without cytoplasmic division microspores pollination Two sperms enter ovule Female gametophyte

Plant Life Histories Annuals complete life cycle in one growing season Biennials live for two seasons; flowers form in second season Perennials grow and produce seeds year after year

Shoot and Root Systems Shoot system produces sugars by photosynthesis carries out reproduction Shoot System Root system anchors the plant penetrates the soil and absorbs water and minerals stores food Root System

Shoot and root systems are interdependent water & minerals sugar SHOOT SYSTEM ROOT SYSTEM

Plant Tissue Systems Ground tissue system Vascular tissue system EPIDERMIS Ground tissue system Vascular tissue system Dermal tissue system VASCULAR TISSUES GROUND TISSUES SHOOT SYSTEM ROOT SYSTEM

Meristems – Where Tissues Originate Regions where cell divisions produce plant growth Apical meristems Lengthen stems and roots Responsible for primary growth Lateral meristems Increase width of stems Responsible for secondary growth

Apical Meristems Lengthen shoots and roots: SAM and RAM activity at meristems Cells that form at apical meristems: new cells elongate and start to differentiate into primary tissues protoderm  epidermis ground meristem  ground tissues procambium  primary vascular tissues

Lateral Meristems Increases girth of older roots and stems Cylindrical arrays of cells vascular cambium  secondary vascular tissues periderm  cork cambium thickening

Made up of only one type of cell Simple Tissues Made up of only one type of cell Parenchyma Collenchyma Sclerenchyma

Morphology of three simple tissue types parenchyma collenchyma sclerenchyma

Parenchyma: A Simple Tissue Comprises most of a plant’s soft primary growth Cells are pliable, thin walled, many sided Cells remain alive at maturity and retain capacity to divide Mesophyll is a type of parenchyma that contains chloroplasts

Collenchyma: A Simple Tissue Specialized for support for primary tissues Cells are elongated, with walls (especially corners) thickened with pectin Makes stems strong but pliable Cells are alive at maturity

Sclerenchyma: A Simple Tissue Supports mature plant parts Protects many seeds Cells have thick, lignified walls and are dead at maturity Two types: Fibers: Long, tapered cells Sclereids: Stubbier cells

Composed of a mix of cell types Complex Tissues Composed of a mix of cell types Xylem Phloem Epidermis

Xylem Conducts water and dissolved minerals Conducting cells are dead and hollow at maturity vessel member tracheids

Phloem: A Complex Vascular Tissue sieve plate Transports sugars Main conducting cells are sieve-tube members Companion cells assist in the loading of sugars sieve-tube member companion cell

Epidermis: A Complex Plant Tissue - Covers and protects plant surfaces - Secretes a waxy, waterproof cuticle - In plants with secondary growth, periderm replaces epidermis

Monocots and Dicots – same tissues, different features 1 cotyledon 2 cotyledons 4 or 5 floral parts 3 floral parts Netlike veins Parallel veins 3 pores 1 pore Vascular bundles dispersed Vascular bundles in ring

Shoot Development shoot apical meristem protoderm procambrium ground meristem cortex procambrium pith primary xylem primary phloem

Bud = undeveloped shoot of meristematic tissue Leaves Internode Axillary bud at node Longitudinal section of terminal bud

Roots also have meristems

Internal Structure of a Dicot Stem - Outermost layer is epidermis - Cortex lies beneath epidermis - Ring of vascular bundles separates the cortex from the pith - The pith lies in the center of the stem

Internal Structure of a Monocot Stem The vascular bundles are distributed throughout the ground tissue No division of ground tissue into cortex and pith

Dicots Monocots Ground tissue system Dermal tissue system Vascular tissue system Dicots and Monocots have different stem and root anatomies

Leaf Gross Structure DICOT MONOCOT petiole axillary bud blade node sheath blade node

Adapted for Photosynthesis Leaves are usually thin High surface area-to-volume ratio Promotes diffusion of carbon dioxide in, oxygen out Leaves are arranged to capture sunlight Are held perpendicular to rays of sun Arrange so they don’t shade one another

Leaf Structure UPPER EPIDERMIS cuticle PALISADE MESOPHYLL xylem SPONGY phloem LOWER EPIDERMIS CO2 one stoma O2

Mesophyll: Photosynthetic Tissue A type of parenchyma tissue Cells have chloroplasts Two layers in dicots Palisade mesophyll Spongy mesophyll

Collenchyma Parenchyma

Leaf Veins: Vascular Bundles Xylem and phloem – often strengthened with fibers In dicots, veins are netlike In monocots, they are parallel

Root Systems

Root Structure Root cap covers tip Apical meristem produces the cap Cell divisions at the apical meristem cause the root to lengthen Farther up, cells differentiate and mature root apical meristem root cap

Internal Structure of a Root Outermost layer is epidermis Root cortex is beneath the epidermis Endodermis, then pericycle surround the vascular cylinder In some plants, there is a central pith

epidermis endodermis cortex pericycle root hair phloem xylem

Root Hairs and Lateral Roots Both increase the surface area of a root system Root hairs are tiny extensions of epidermal cells Lateral roots arise from the pericycle and must push through the cortex and epidermis to reach the soil new lateral root

Secondary Growth Occurs in perennials A ring of vascular cambium produces secondary xylem and phloem Wood is the accumulation of these secondary tissues, especially xylem

Secondary Growth

Woody Stem periderm (consists of cork, cork cambium, and secondary cortex) secondary phloem HEARTWOOD SAPWOOD BARK vascular cambium

Annual Rings Concentric rings of secondary xylem Alternating bands of early and late wood Early wood Xylem cells with large diameter, thin walls Late wood Xylem cells with smaller diameter, thicker walls

Types of Wood Hardwood (oak, hickory) Softwood (pine, redwood) Dicot wood Xylem composed of vessels, tracheids, and fibers Softwood (pine, redwood) Gymnosperm wood Xylem composed mostly of tracheids Grows more quickly