P1253814444ziAHV

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Outline

• Plant Organs
• Roots
• Stems
• Leaves
• Monocots vs. Eudicots
• Epidermal Tissue
• Vascular Tissue

• Roots
• Organization
• Diversity
• Stems
• Organization
• Diversity
• Leaves
• Organization
• Diversity

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Plant Organs

• Roots
• Generally, the root system is at least equivalent
  in size and extent to the shoot system
• Anchors plant in soil
• Absorbs water and minerals
• Produces hormones
• Root hairs
• Projections from epidermal root hair cells
• Greatly increase absorptive capacity of root

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Organization of Plant Body
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Vegetative Organs of Several Eudicots
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Stems

• Shoot system of a plant is composed of the stem,
  branches, and leaves
• Stem is the main axis of a plant that elongates
  and produces leaves
• Nodes occur where leaves are attached to the stem
• Internode is region between nodes
• Stem also has vascular tissue that transports
  water and minerals

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Leaves

• Leaves are the major part of the plant that
  carries on photosynthesis
• Foliage leaves are usually broad and thin
• Blade - Wide portion of foliage leaf
• Petiole - Stalk attaches blade to stem
• Leaf Axil - Axillary bud originates
• Tendrils - Leaves that attach to objects
• Bulbs - Leaves that store food

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Monocot vs. Eudicot

• Monocots (Single cotyledon)
• Cotyledons act as transfer tissue
• Root vascular tissue occurs in ring
• Parallel leaf venation
• Eudicots (Two cotyledons)
• Cotyledons supply nutrients to seedlings
• Root phloem located between xylem arms
• Netted leaf venation

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Flowering PlantsMonocots or Eudicots
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Plant Tissues

• Epidermal Tissues
• Contain closely packed epidermal cells
• Covered with waxy cuticle
• Roots contain root hairs
• Lower leaf surface contain stomata
• Woody plants covered by cork

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Modifications of Epidermal Tissue
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Ground Tissue

• Ground tissue forms bulk of a plant
• Parenchyma cells
• Least specialized and are found in all organs of
  plant
• Can divide and give rise to more specialized
  cells
• Collenchyma cells
• Have thicker primary walls
• Form bundles underneath epidermis
• Flexible support to immature regions of the plant

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Ground Tissue Cells
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Ground Tissue

• Sclerenchyma cells
• Have thick secondary walls impregnated with
  lignin
• Most are nonliving
• Primary function is to support mature regions of
  the plant
• Fibers
• Sclereids

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Vascular Tissue

• Xylem transports water and minerals from the
  roots to the leaves
• Tracheids
• Long, with tapered ends
• Pits in end walls
• Vascular rays
• Fibers
• Vessel Elements
• Larger, with perforated plates in their end walls

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Xylem Structure
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Ground Tissue

• Sclerenchyma cells
• Have thick secondary walls impregnated with
  lignin
• Most are nonliving
• Primary function is to support mature regions of
  the plant
• Fibers
• Sclereids

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Vascular Tissue

• Phloem transports sucrose and other organic
  compounds from the leaves to the roots
• Sieve-tube members are conducting cells
• Contain cytoplasm but no nuclei
• Channels in end walls
• Plasmodesmata extend from one cell to another
  through sieve plate

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Phloem Structure
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Organization of Roots

• Root apical meristem
• Located in the root tip
• Protected by root cap
• Primary meristems are in the zone of cell
  division
• Zone of maturation contains fully differentiated
  cells

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Tissues of Eudicot Root

• Epidermis
• Cortex
• Endodermis
• Casparian Strip
• Vascular Tissue
• Pericycle

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Eudicot Roots
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Branching of Eudicot Root
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Organization of Monocots Roots

• Monocot roots
• Ground tissue of roots pith is surrounded by
  vascular ring
• Have the same growth zones as eudicot roots, but
  do not undergo secondary growth

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Monocot Root
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Root Diversity

• Primary root (taproot) - Fleshy, long single
  root, that grows straight down
• Stores food
• Fibrous root system - Slender roots and lateral
  branches
• Anchors plant to soil
• Adventitous roots - Roots develop from organs of
  the shoot system
• Prop roots

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Root Diversity

• Haustoria
• Rootlike projections that grow into host plant
• Make contact with vascular tissue and extract
  water and nutrients
• Mycorrhizas
• Associations between roots and fungi
• Assist in water and mineral extraction
• Root nodules - Contain nitrogen-fixing bacteria

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Root Diversity
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Organization of Stems

• Shoot apical meristem
• Produces new cells that elongate and increase
  stem length
• Protected by terminal bud
• Enveloped by leaf primordia
• Specialized primary meristems
• Protoderm
• Ground Meristem
• Procambium

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Woody Twig
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Shoot tip and Primary Meristems
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Herbaceous Stems

• Mature nonwoody stems exhibit only primary growth
• Outermost tissue covered with waxy cuticle
• Stems have distinctive vascular bundles
• Herbaceous eudicots - Vascular bundles arranged
  in distinct ring
• Monocots - Vascular bundles scattered throughout
  stem

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Herbaceous Eudicot Stem
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Monocot Stem
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Woody Stems

• Woody plants have both primary and secondary
  tissues
• Primary tissues formed each year from primary
  meristems
• Secondary tissues develop during first and
  subsequent years from lateral meristems

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Woody Stems

• Woody stems have no vascular tissue, and instead
  have three distinct regions
• Bark
• Wood
• Pith

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Secondary Growth of Stems
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Bark

• Bark of a tree contains cork, cork cambium, and
  phloem
• Bark can be removed, but it is harmful to the
  plant due to lack of organic nutrient transport
• Cork cells are impregnated with suberin
• Gas exchange is impeded except at lenticels

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Wood

• Wood is secondary xylem that builds up year after
  year
• Vascular cambium dormant during winter
• Annual ring is made up of spring wood and summer
  wood
• In older trees, inner annual rings, heartwood, no
  longer function in water transport

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Three-year-old Woody Twig
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Tree Trunk
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Stem Diversity

• Stolons
• Above-ground horizontal stems
• Produce new plants when nodes touch the ground
• Rhizomes
• Underground horizontal stems
• Contribute to asexual reproduction
• Variations
• Tubers - Enlarged portions functioning in food
  storage
• Corms - Underground stems that produce new plants
  during the next season

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Stem Diversity
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Leaf Diversity

• Blade of a leaf can be simple or compound
• Leaves are adapted to environmental conditions.
• Shade leaves
• Spines
• Climbing leaves

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Leaf Structure
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Classification of Leaves
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Leaf Diversity
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Review

• Plant Organs
• Roots
• Stems
• Leaves
• Monocots vs. Eudicots
• Epidermal Tissue
• Vascular Tissue

• Roots
• Organization
• Diversity
• Stems
• Organization
• Diversity
• Leaves
• Organization
• Diversity

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