Plant Structure, Growth, and Development (Ch. 35)

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Plant Structure, Growth, and Development(Ch. 35)
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What are Angiosperms?
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Angiosperm Body

• 2 Taxonomic classes
• monocots
• eudicots
• Monocots
• One cotyledon
• Parallel veins
• Floral parts in 3s
• Fibrous Roots
• Eudicots
• Two cotyledons -
• Netlike veins
• -Floral parts in 4s and 5s
• Tap root

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Angiosperm Body

• Need to be able to inhabit soil and air at the
  same time
• roots and shoots
• Plant morphology
• study of the external structure
• arrangement of flower parts, etc.
• Plant anatomy
• study of the internal structure
• arrangement of cells, tissues in a leaf, etc.
• Tissue groups of cells, consisting of one or
  more types, that perform a specialized function
• Organ consists of several types of tissues that
  together carry out specific functions

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Angiosperm Body

• Two basic systems
• root system
• aerial shoot system (stems, leaves, flowers)
• Vascular Tissues
• transport materials
• xylem transports water and dissolved minerals
• phloem transports food

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Root System

• Anchoring, absorbing water and minerals, storing
  carbohydrates
• Taproot system
• one large, vertical root
• mostly eudicots
• firm anchorage one large vertical root
• stores lots of reserve food
• gives rise to lateral roots

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Root System

• Fibrous root system
• mat of threadlike roots
• mostly monocots
• extensive exposure to soil, water, minerals
• concentrated in topsoil prevents erosion

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Root System

• Adventitious roots
• plant organ that grows in an unusual location
• arising above ground or from stems/leaves
• Root hairs
• thin, tubular extension of a root epidermal cells
• increase SA near root tip

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Root System

• Mycorrhizae
• mutualistic relationship between fungi and roots
• Root nodules
• contain symbiotic bacteria to convert atmospheric
  nitrogen to compounds usable by the plant

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Modified Roots
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Shoot System

• Vegetative shoots
• Stems and leaves
• Floral shoots
• Flowers
• Stem
• Alternating system of nodes and internodes
• Raises or separates leaves
• Raise reproductive structures

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Shoot System - Stems

• Nodes
• where leaves attach to stems
• Internodes
• segment of stem between nodes
• Axillary bud
• embryonic side shoot
• has potential to form a branch shoot
• usually dormant in young plants
• pruning

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Shoot System - Stems

• Terminal (apical) bud
• bud on shoot tip composed of developing leaves
  and a compact series of nodes and internodes
• where most of the growth of a young plant occurs
• May inhibit growth of axillary buds
• apical dominance

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BELL RINGER
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Modified Stems

• Stolons
• Runners allow plant to colonize a large area
  reproduce asexually
• Rhizomes
• Horizontal stem that grows below ground
• Tubers
• Swollen ends of rhizomes store food
• Bulbs
• Vertical, underground shoots

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Modified Stems
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Shoot System - Leaves

• Main photosynthetic organ
• Blade
• Joined to node by a petiole
• Venation (vascular tissue)
• parallel
• netted
• Classification
• shape
• spatial arrangement
• venation

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Modified Leaves

• Tendrils on vines
• Spines of cacti
• Storage
• Reproductive
• Bracts

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Dermal, Vascular, and Ground Tissues

• Tissue system
• A functional unit connecting all of the plants
  organs
• Dermal tissue system
• Outer protective covering
• Epidermis in nonwoody plants
• Cuticle
• Periderm in woody plants

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Dermal, Vascular, and Ground Tissues

• Vascular tissue system
• Long distance transport b/w roots and stems
• Xylem and phloem
• Collectively called the stele
• Ground tissue system
• If internal to the vascular tissue ? pith
• If external to the vascular tissue ? cortex

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Plant Cells

• Protoplast
• contents of a plant cell not including the cell
  wall
• Lignin
• Structural component of cell walls
• All start out similar to parenchyma cells become
  more specialized
• Can generate an entire plant from one parenchyma
  cell

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Plant Cells

• Parenchyma cells
• typical plant cell
• chloroplasts for photosynthesis
• large central vacuole
• store starch
• comprise fleshy tissue of fruits
• Collenchyma cells
• unevenly thick primary walls
• support for young plants without restraining
  growth
• living and flexible throughout life

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Plant Cells

• Sclerenchyma cells
• rigid, thick secondary walls with lignin
• function only in support
• may be dead at maturity but produce secondary
  walls before protoplast dies
• Sclereids
• Very thick cell lignified cell walls nutshells
  seed coats
• Fibers
• Long, slender and tapered

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Plant Cells

• Water-conducting cells of xylem
• dead at functional maturity
• allow water to flow from cell to cell
• tracheids
• In nearly all vascular plants
• Water moves through pits
• vessel elements
• Angiosperms and some gymnosperms
• Water moves through perforation plates

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Plant Cells

• Food-conducting cells of phloem
• alive at functional maturity
• sieve-tube cells make the sieve tube
  elements/members that transport sucrose and other
  organic nutrients
• sieve plate
• Pores that allow flow from cell to cell
• companion cells
• Ribosomes and nucleus serve the sieve tube cell
  too

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Figure 35.12 Locations of major meristems an
overview of plant growth
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Meristems generate cells for primary and
secondary growth

• Begins with germination and occurs throughout
  life of plant
• Indeterminate growth
• Meristems
• perpetually undifferentiated tissues
• Apical meristems
• Responsible for primary growth (growth in length)
• Lateral meristems
• Responsible for secondary growth (growth in
  thickness)

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Meristems generate cells for primary and
secondary growth

• Two types of lateral meristems
• Vascular cambium
• Add layers of vascular tissue called secondary
  xylem (wood) and secondary phloem
• Cork cambium
• Replaces the epidermis with thicker, tougher
  periderm

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Plant Growth

• Finite life span
• genetically environmentally determined
• annuals, biennials, and perennials
• Annuals
• Complete their life cycle in a year
• Cereal grains, legumes, wildflowers
• Perennials
• Live many years
• Trees, shrubs, some grasses
• Biennials
• Life span generally 2 years
• Live through an intervening cold period between
  vegetative growth and flowering
• Beets, carrots

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Figure 35.14 Primary growth of a root
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Primary Growth Lengthens Roots and Shoots

• Primary growth of roots
• pushes roots through soil root cap covers apical
  meristem
• Zone of cell division
• apical and primary meristems
• Zone of cell elongation
• elongate in size
• Zone of maturation
• specialize in function

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Primary Growth Lengthens Roots and Shoots

• Epidermis
• Ground tissue
• Vascular tissue
• Stele
• Endodermis
• Pericycle

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Primary Growth Lengthens Roots and Shoots

• Primary growth of shoots
• Apical meristems give rise to primary meristems
• Leaf primordia give rise to leaves
• Shoot elongation is due to lengthening of
  internode cells below the shoot tip
• Branching occurs due to activation of axillary
  buds

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Tissue Organization of Stems

• Epidermis
• Covers stems
• Vascular tissue in bundles
• Axillary buds meristems develop lateral shoots
• Parenchyma, collenchyma, and scelerenchyma cells
  are present

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Tissue Organization of Leaves

• Epidermis
• tightly locked cells
• protect from damage pathogens
• waxy cuticle
• Stomata
• pores on underside of leaf
• site of gas exchange
• Guard cells
• control stomata opening for gas exchange
• Flaccid ? stomata are closed due to lack of water

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Tissue Organization of Leaves

• Mesophyll
• Ground tissue of leaf between epidermal layers
• palisade parenchyma
• upper half of leaf
• spongy parenchyma
• air spaces to allow O2 and CO2 to circulate
• lower half of leaf

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Tissue Organization of Leaves
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Vascular Cambium and Secondary Vascular Tissue

• Secondary growth of stems
• Stems and roots of woody plants
• vascular cambium
• transport and storage of starch
• Adds secondary xylem (wood) and secondary phloem
• cork cambium
• protective layers
• Bark (refers to all tissues external to vascular
  cambium)
• phloem, phelloderm, cork cambium, cork
• Secondary growth of roots

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• An overview of primary and secondary growth

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Cork Cambium and Production of Periderm

• Phelloderm
• Thin layer of parenchyma cells that forms to the
  interior of the cork cambium
• Accumulation of cork cells
• Deposit suberin in walls then die
• Protects from water loss, physical damage,
  pathogens
• Lenticels
• Small, raised areas in the periderm
• Help cells to exchange gases

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Growth, Morphogenesis, and Cell Differentiation
Produce the Plant Body

• Development
• Specific series of changes by which cells form
  tissues, organs, and organisms
• Growth
• Irreversible change in size
• Cell division and expansion
• Morphogenesis
• Process that gives a tissue, organ, or organism
  its shape and determines the positions of cell
  types
• Pattern formation
• Differentiation
• Process by which cells with the same genes become
  different from one another
• Control of gene expression