Lecture 3: Plant anatomy and physiology

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Lecture 3 Plant anatomy and physiology

• by
• Edgar Moctezuma, Ph.D.

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Today

• Announcements
• Plant Anatomy
• Cells
• Tissues
• Organs
• Plant Physiology
• Water sugar transport
• Plant hormones

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Announcements

• Labs start this week get your lab manual.
• BSCI 125 students if you have the following
  sections
• 1109, 1110 Tues. 330-530 or,
• 1113, 1114 Wed. 12-2 or,
• 1115, 1116 Wed. 3-5 or
• 1123, 1124 Thurs. 330-530, and you can switch
  to an open section (Monday or Wed. 900-1100),
  please try to do so. Thanks!
• Taking care of your plant
• Do not overwater it! Water only when soil is dry
  to the touch.
• Place near a sunny window.

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From smallest to largest plants
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What is plant anatomy?

• ANATOMY study of the structure of organisms
  looking at cells, tissues
• (Morphology Study of form)

What is plant physiology?

• PHYSIOLOGY study of the function of cells,
  tissues, organs of living things
• and the physics/chemistry of these functions

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Structure correlates to function

• Always keep in mind that in plant anatomy,
  morphology physiology

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• How can water move from
• the ground
• all the way
• to the top
• of a 100 m
• tall redwood
• tree?

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Plant Anatomy Cells

• Plant cells are basic building blocks
• Can specialize in form and function
• By working together, forming tissues, they can
  support each other and survive
• Levels of organization
• atoms gt molecules gt cells gt tissues gt organs gt
  whole plant gt pop.

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Plant Tissues Types

• All plant organs (roots, stems, leaves) are
  composed of the same tissue types.
• There are three types of tissue
• 1. Dermal outermost layer
• 2. Vascular conducting tissue, transport
• 3. Ground bulk of inner layers

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1. Dermal tissue

• Epidermis is the outermost layer of cells
• Like the skin of animals
• In stems and leaves, epidermis has cuticle, a
  waxy layer that prevents water loss.
• Some have trichomes, hairs.
• Root epidermis has root hairs, for water and
  nutrient absorption

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2. Vascular tissue

• Transports water and organic materials (sugars)
  throughout the plant
• Xylem transports water and
• dissolved ions from the root
• to the stem and leaves.

• Phloem carries dissolved sugars
• from leaves to rest of the plant

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Xylem

• Transports water and dissolved minerals
• Tracheids long, thin tube like structures
  without perforations at the ends
• Vessel elements short, wide tubes perforated at
  the ends (together form a pipe, called vessel).
• Both cells have pits (thin sections) on the walls
  

Tracheids
Vessel elements
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Xylem cells

• Xylem cells are dead!
• They are hollow cellsand consist only ofcell
  wall

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Phloem

• Cells that transport organic materials (sugars)
• Phloem cells are ALIVE! (unlike xylem)
• However, they lack nucleus and organelles

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Phloem transports sugars

• Phloem composed of cells called sieve tube
  members (STM)
• Companion cells join sieve tube members, are
  related, and help to load materials into STM
• End walls of STM have large pores called
• sieve plates

Companion cells
Sieve tube member
Sieve plates
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3. Ground tissue

• Makes up the bulk of plant organs.
• Functions Metabolism, storage and support.

Root Stem Leaf
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Plant Organs

• Organs tissues that act together to serve a
  specific function
• Roots
• Stems
• Leaves

Dermal Vascular Ground
Dermal Vascular Ground
Dermal Vascular Ground
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Functions of plant organs

• ROOTS Anchorage, water/nutrient absorption from
  soil, storage, water/nutrient transport
• STEMS Support, water/nutrient transport
• LEAVES Photosynthesis (food production)

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ROOTS

• ROOTS the hidden half
• Functions of roots
• Ancorage
• Absorption of water dissolved minerals
• Storage (surplus sugars, starch)
• Conduction water/nutrients

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Anatomy of a root
epidermis
cortex
vascular
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Root Epidermis

• Outermost, single layer of cells that
• Protects (from diseases)
• Absorbs water and nutrients
• ROOT HAIRS tubular extensions
• of epidermal cells.
• Increase surface area of root,
• for better water/nutrient
• absorption

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Root Hairs water and mineral absorption
Root hairs increase surface area for
better absorption
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Root Cortex

• Stores starch, sugars and other substances

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Root Ground tissue

• In roots, ground tissue (a.k.a. cortex) provides
  support, and
• often stores sugars and starch
• (for example yams, sweet potato, etc.)

Youre not a yam, youre a sweetpotato!
Hey! I yam what I yam, man!
cortex
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Root Cortex Endodermis

• Endodermis the innermost layer of the cortex

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Root cortex Casparian strip

• The Casparian strip is a water-impermeable strip
  of waxy material found in the endodermis
  (innermost layer of the cortex).
• The Casparian strip helps to control the uptake
  of minerals into the xylem they have to go
  through the cytoplasm of the cell!

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STEMS

• Above-ground organs (usually)
• Support leaves and fruits
• Conduct water and sugars
• throughout plant (xylem and phloem)

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Stem anatomy

• Dermal, ground and vascular tissues

epidermis
cortex
pith
Vascular bundles
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Types of Stems
Monocot stem Dicot stem Root
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Types of stems

• Herbaceous vs. Woody stems

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Tissues of stems

• Epidermis (Dermal tissue type)
• Provides protection
• Has cuticle (wax) prevents water loss
• Trichomes (hairs) for protection, to release
  scents, oils, etc.

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Stem Vascular tissue

• Vascular bundles composed of both xylem and
  phloem
• Xylem
• Conducts water
• Support
• Phloem
• Conducts food
• Support

Vascular cambium
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Vascular cambium

• Occurs in woody stems
• Vascular cambium located in the middle of the
  vascular bundle, between xylem and phloem

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Vascular tissue Trees

• Vascular tissue is located on the outer layers of
  the tree.

bark
wood
phloem
Vascular cambium
xylem
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Girdling cutting around a tree

• Damages the phloem and xylem, eventually killing
  the tree!

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Vascular tissue forms rings in trees

• Annual rings xylem formed by the vascular
  cambium during one growing season
• One ring one year

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History of the tree annual rings
Dendrochronology tree time-keeping
1917 1945 Tree Survives two World Wars
1776 Declaration of US independence
1969 Man lands on Moon
1492 Columbus lands in the Americas
1620 Pilgrims land in Plymouth, Mass.
1861 Start of Civil War
1489 Tree is planted by Native American
1971 Birth Year of the IDIOT who cut down this
tree!!!
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Ground tissue Cortex pith

• Stores food (e.g. potato)
• Site of Photosynthesis (when green)
• Support cells

cortex
pith
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LEAVES

• Photosynthetic factories of the plant
• Function Photosynthesis food
• production for the whole plant
• Blade Flat expanded area
• Petiole stalk that connects
• leaf blade to stem, and
• transports materials

BLADE
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Leaf Anatomy

• Leaf anatomy is correlated to photosynthesis
• Carbon dioxide Water ? sugars oxygen

dermal
ground
vascular
dermal
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Leaf epidermis

• Is transparent so that sun light can go
  through.
• Waxy cuticle protects against drying out
• Lower epidermis stomata with guard cells for
  gas exchange (CO2, H2O in O2 out)

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Leaf epidermis

• Trichomes (give fuzzy texture)

(Panda plant)
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Leaf vascular tissue

• VEINS ? vascular tissue of leaves.
• Veins are composed of xylem (water transport)
  phloem (food transport)

and bundle sheaths, cells surrounding
the xylem/phloem for strength support
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Leaf Mesophyll

• Middle of the leaf (meso-phyll)
• Composed of photosynthetic ground cells
• Palisade parenchyma
• (long columns below epidermis
• have lots chloroplasts for
• photosynthesis)
• Spongy parenchyma
• (spherical cells)
• with air spaces around,
• (for gas exchange)

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Plant water transport

• How can water move from
• the ground
• all the way
• to the top
• of a 100 m
• tall redwood
• tree?

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Water transport in plants

• The same way we drink soda
• from a straw!
• Waters great
• cohesive forces (molecules
• sticking to each other)
• and adhesive forces
• (attaching to walls of xylem cells)

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Transpiration-cohesion Theoryfor water transport
in the xylem

• Evaporation of water in the leaves (through
  stomates) generates the sucking force that
  pulls adjacent water molecules up the leaf
  surface

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Water transport (cont.)

• Like a long chain, water molecules pull each
  other up the column.
• The column goes from roots ? leaves.
• Whats amazing is that the
• water moves up by using the suns
• evaporative energy
• Plants control transpiration by opening/closing
  stomata

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Sugar translocation

• 1. Sugars made in leaf mesophyll cells (source)
  diffuse to phloem cells in the vascular bundles.
• 2. Companion cells load dissolved sugars into the
  phloem STM using energy (ATP).
• 3. Water moves into cells with high sugar
  concentration.
• 4. Osmotic water flow generates a high hydraulic
  pressure that moves dissolved sugars through the
  phloem to the rest of the plant (sink).

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Pressure flow in phloem

• Sugars made in the leaves are loaded into
  companion cells and into phloem STM.
• Water (from xylem) moves in by osmosis, creating
  pressure flow down the phloem.

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Plant Hormones

• Chemical compounds produced by plants
• Effective at very low concentrations
• Five major hormone groups are
• Auxins
• Gibberellins
• Cytokinins
• Abscisic Acid
• Ethylene

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1. AUXINS

• Promote cell growth
• Involved in
• gravitropism
• and phototropism
• Control fruit development

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2. Gibberellins

• Promote stem elongation

3. Cytokinins

• Promote cell division and
• organ differentiation

4. Abscisic Acid

• Promotes seed dormancy
• Causes stomata closing

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5. ETHYLENE

• Gaseous hormone,
• very simple formula (C2H4)
• Ethylene promotes
• fruit ripening!

Air Ethylene
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One rotten apple spoils the barrel

• Why?
• Probably due to ethylene!
• Rotten apple producing
• lots of ethylene!
• Autocatalytic
• As a response to injury

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Avocado ripening

• Place in a paper bag, with a ripe banana!