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Plants
Plant Nutrition
• Review Photosynthesis
Plant Reproduction
• Asexual: Vegetative Propagation
– Ex. Cuttings, Bulbs, Runners, Sporulation etc.
• Sexual:
– Meiosis and fertilization
Background: Land Plant Groups
• Mosses (Most Ancient)
– Need High Moisture for Reproduction
• Ferns
– Need High Moisture for Reproduction
• Seed-Producing Plants
– Gymnosperms (Conifers)
– Angiosperms (Flowering Plants)
Plant Reproduction Intro
• Diplontic Organisms
– Ex. Animals, brown algae, some fungi
– Gametes (sperm and eggs) are the only
haploid cells in life cycle
– Mature organism is Diploid
Plant Reproduction Intro
• Haplontic Organisms
– Ex. Protists,fungi, some green algae
– zygote is only diploid cell in life cycle
– Zygote undergoes meiosis to produce haploid
spores
– Spore develops into a mature haploid
organism
Plant Reproduction
• Alternation of Generations Organisms
– Ex. Plants, some fungi
– A diploid cell undergoes meiosis to produce
haploid spores which develop in the
Gametophyte stage of life cycle
– Gametophytes forms gametes by mitosis
– Gametes fuse to form a diploid zygote
– Zygote develops into the diploid Sporophyte
stage of life cycle
Alteration or Alternation of
Generations
• The phases of life of a plant
• Plants switch between a:
– Haploid Gametophyte stage
• Generated by meiosis
– And a Diploid Sporophyte stage
• Generated by fertilization
Alteration of Generations
• Sporophyte
– Makes spores (n)
– Spores hatch into gametophyte stages
• Gametophyte
– Makes gametes (sperm and egg)
– Fertilization results in a sporophyte
Dominant Generation
• Mosses: Gametophyte
• Ferns: Sporophyte
• Seed-Producing Plants: Sporophyte
Life Cycle of Moss
Life cycle of a Fern
Heterosporous Plants
• Megaspore
– Develops into female gametophyte
(Megagametophyte) that makes eggs
• Microspore
– Develops into male gametophyte
(microgametophyte) that makes sperm
Life cycle of a Pine Tree
Lifecycle of Angiosperms (Know!!!)
• Most successful plant group
• The flower is the reproductive part of plant
Anatomy of a flower
Receptacle
=holds nectar
Parts of Flower
• Female Part (Pistil)
– Stigma=Sticky, catches pollen
– Style=tunnel that sperm of pollen travel down
– Ovary=contain ovules which contain eggs
• Fertilization of ovules causes wall of ovary to thicken and
become a fruit
• Male Part (Stamen)
– Filament=holds up high the anther
– Anther=produce haploid spores via meiosis which
then develop into pollen with sperm inside
Parts of Flower
• Pedicel= connects flower to branch
• Sepals=enclose flower bud
– A ring of sepals=calyx
• Petals=Attract pollinators to transfer pollen
– A ring of petals=corolla
• Receptacle=holds nectar (sugar water)
Flower Types
• Pistillate=only female parts
• Stamenate=only male parts
• Perfect or complete=both parts
Pollen
Pollination
=pollen transfer from anther to stigma
• Self Pollination=transfer of pollen from
anther to stigma of flowers on SAME plant
(can be same flower)
• Cross Pollination=transfer pollen from one
plant to a different plant
Mechanisms of Pollination
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Insect
Bird
Wind
Rain
ManArtificial
Pollinator comes and picks up
pollen
Pollen germinates on stigma
A pollen tube grows down
style
Two sperm nuclei migrate
down towards ovules in
ovary
Ovary with
4 ovules
Polar Nuclei
{1Ovule
Egg
Sperm
Doorway into ovule is the
Microphyle
What Now?
• Ovule wall becomes the seed coat
• 2n zygote becomes the plant embryo
• 3n Endosperm becomes food supply for
baby
• Wall of ovary swells and becomes a fruit
Types of Fruit
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Tomato
Walnut
Pea pods
Corn
squash
Types of Fruit
• Simple Fruit=One
ovary of one flower
ex. Cherry
• Aggregate
Fruit=Several ovaries
on one flower ex.
Strawberries
Types of Fruit
• Multiple Fruit=Many simple fruits fused
together
Seed Dispersal
• Fruits eaten and
animal poops out
seeds
• Wind blows seeds
Seed Dispersal
• Catch ride on animal
• Explosion
Seed Dispersal
• Via water
Seed Anatomy
• Two Classes of Seed:
– Dicot Type-From Dicot Plants
• Two cotyledons or “seed leaves”
– Monocot Type-From Monocot Plants
• One cotyledon or “seed leaf”
Parts of Seed
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Cotyledon=“seed leaf”, nutrient storage
Epicotyl= grows into upper part of plant
Hypocotyl=grows into midsection of plant
Radicle=embryonic root
Endosperm=food storage
Seed Coat=surrounds seed
Embryo=baby plant
Dicot Seed
Ex. Bean
Dicot seeds
Monocot Seed
Seed
Coat
Epicotyl
Hypocotyl
Monocots
Seed Germination
• Seeds remain dormant until appropriate
conditions are met
• Appropriate Conditions:
– Water (can loosen seed coat and wash out
inhibitory chemicals)
– Oxygen
– Proper temp.
Plant Structure
Organs of a Plant:
– Roots
• Absorb minerals and water
• Anchorage
– Stems
• Hold plant upright and
support leaves and other
structures
– Leaves
• photosynthesis
– Reproductive structures
• Ex. Flowers and Cones
Plant Structure
• Tissues of plants:
– Meristematic
• Areas of intense cell
division (-helps plants grow
in length and width)
– Located in the ends of
stems and roots (a.k.a.
Apical
Meristems)=these
cause for growth in
length
Meristematic
Zone
Apical
Meristem at
end of a
stem
Apical Meristem at end
of root
– Meristematic Tissue
• In woody plants
there is a
Cambium
Meristem around
the stems and
roots that cause
for growth in
width
Plant Structure
• Tissues of Plants:
– Protective Tissues
• Epidermis
– makes waxy Cutin of Cuticle
Layer
– Protects against infection and
water loss
• Cork
– Covers woody stems and
roots
– Adult cork cells are dead
– Waterproofs and protects
against infection
Plant Structures
• Tissues:
– Vascular Tissues
• Xylem (-wood)
– Water and mineral transport from roots to leaves
– Supports
– Mature cells are dead
• Phloem
– Food and dissolved material transport in both directions
– Live cells
Xylem
Xylem
Components:
– Tracheids with pits
– Vessel Elements
Phloem
Phloem
• Components:
– Sieve Cells
• No Nucleus
• For sieve tubes
– Companion cells
• Supply genetic info to Sieve Cells
Plant Structures
• Tissues:
– Ground Tissue
For Food Storage and Support
• Parenchyma
• Collenchyma
• Sclerenchyma
Roots
• Types
– Primary Root
• Main or first root
– Secondary Root
• Branch off of primary
Root Systems
• Taproots
– Primary root dominant, deep and fleshy
– Ex. Carrots, turnips
Root Systems
• Fibrous roots
– Numerous branching roots
– Ex. Grass, corn
Root Systems
•
Adventitious root
systems
=roots that come from the
stem or leaves NOT
the primary root
1. Prop Roots=grow from
stem and support
Adventitious roots
2. Climbing roots
=grow from stem and attach plant to
support structure
Adventitious roots
3. Aerial roots
=roots that are suspended and absorb
moisture from air
Cross section of roots
Stems
• Types
– Herbaceous Stems
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Soft, green, juicing stems
Last one or two seasons
Little growth in width
Ex. Corn, tomatoes
Monocot stem
Stems
• Types
– Woody stems
• Have growth in width
due to vascular
cambium
• Tough, cold resistant
stem
• Build up layers of xylem
but only retain youngest
phloem
Note: Most woody plants are
Monocots
Sapwood vs. heartwood
Stems
Terminal bud with
apical meristem
inside
Terminal bud
scars
Lenticels=holes in stem for gas exchange
Leaves
• Broad, flat,
photosynthetic
Veins in leaf
contain xylem
and phloem
Leaf cross-section
Palisade
Spongy
Leaf parts
• Cuticle Layer=Waxy, top and bottom,
prevents water loss
• Epidermis=protection, bottom layer has
stomates that allow for gas exchange
• Guard cells=cause for the opening or
closing of the stomates (Have Cloroplasts)
When
light
outside,
use ATP
to pump
solute
Leaf parts
• Mesophyll Layer
– Palisade sub layer: Most photosynthesis here
– Spongy sub layer: Gas exchange and
photosynthesis
• Veins
– Have xylem and phloem
– Display a venation
Venation
Monocots have parallel venation patterns
Dicots have netted venation patterns
Tracheophyes:
Vascular Plants,
true leaves,
stems and roots
(Ferns, Conifers,
Angiosperms)
Bryophytes: No roots, stems,
leaves, xylem or phloem ex.
Mosses, liverworts and hornworts
Water and Plants
• Water Lost:
– Transpiration
• Plants lose water from
evaporation through
stomates
• Transpiration rate for
large tree=720 L/12hrs
Water and Plants
• Water Gained
– Capillary Action
• Water sticks to walls of xylem
• Alone, not enough to get water up tree
– Root Pressure
• Solutes pumped into xylem
• Ground water follows and creates pressure
• Alone, not enough
– Transpirational pull
• Water evaporates and pulls through H-bonds
other water molecules up xylem
Water and Sugar
• Sugars made via photosynthesis in leaves
and maybe stems
• Sugars travel in phloem up and down
• Cells of phloem are alive
Plants and Sugar Movement
• Translocation
– Movement related to
concentration
gradients of sugar
and the osmosis of
water
– Pressure-flow
theory
Minerals needed by plants
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Phosphorus
Magnesium-****needed for chlorophyll
Iron-electron transport chain
Calcium
sulfur
• Auxins
Plant Hormones
– Affect growth of plant
(promote and inhibit)
– Stimulate cell
lengthening
– Ex. IAA
• Made in terminal buds
and inhibits lateral buds
• Pruning concept
– Affect Abscission
Plant Hormones
• Gibberellins
– Affect growth
– Located throughout plant
Plant Hormones
• Ethylene
– Stimulates fruit
ripening
Plant Hormones
• Cytokinins
– Important for seed germination
• Abscisic Acid
– Needed for leaf shedding and plant dormancy
initiation
Plant Tropisms
• Positive
Tropism=growth
towards a stimulus
• Negative
stimulus=growth away
• Phototropism=growth
towards light
Plant Tropisms
• Geotropism
– Growth related to pull of gravity
Plant Tropisms
• Thigmotropism
– Growth related to touch
Plant Tropisms
• Hydrotropism
– Growth related to water source
Nastic Movements
• Plant movement
– Stimulus-directed but independent of its direction
Photoperiodism
• Plant responses (ex. Flowering, leaves
dropping) as related to length of night.
Short day plants=long night plants (winter)
Long day plants=short night plants (summer)
Photoperiodism