Exam 2 - Notes

Chapter 35
Chapter 36
Chapter 37
Chapter 38
Chapter 39

Chapter 35

Introduction to Plants

Kingdom Plantae

We will primarily be discussing the angiosperms
- Phylum Anthophyta
Flowers and fruits
- Only group that does/has these things
Advanced traits
- Seeds
- Advanced vascular tissues

From seed to seed

The life of a flowering plant

Seeds
- reproductive structures produced by angiosperms and other seed plants
- usually the result of sexual reproduction
- contains embryos that develop into seedlings upon germination
- has survival value

Alternation of Generations

Exhibited by all plants (and plant-like organisms) that have sexual reproduction
There is an alternation between a diploid (2N) form [sporophyte] and a haploid (1N) form [gametophyte]

Gametophyte (haploid)

Gamete-producing plant fomr
multicellular
microscopic in flowering plants
- female
  - embryo sac with egg
- male
  - pollen grain
grow and develop within flowers of angiosperms
produces gametes by mitosis/cytokineses

Sporophyte (diploid)

multicellular
large "plant" in flowring plant
produces haploid spores by meiosis (reduction)
- called meiospores

The plant embryo

Fertilization (syngamy) results in the formation of a diploid zygote, which undergoes mitosis to form an embryo (multicellular)
the embryo is a sporophyte that lies dormant in the seed with a supply of stored food and a seed coat
may lay dormant for long periods until conditions are favorable

The plant body

Composed of three organ types

stems
leaves
roots

Shoot system

stem
- produce leaves and branches and bear the reproductive structures
leaves
- flattened structure specialized for photosynthesis

Root system

roots
- Provide anchorage in the soil and foster efficient uptake of water and minerals
- can store food

Growth

Indeterminate growth
- increasing in size as long as the plant is alive
grows into a seedling and then a mature plant
Plant growth occurs by 3 means
- Increase in number of cells
  - cellular reproduction
    - (mitosis/cytokineses)
- increase in cell size
  - elongation
- increase in weight/mass

Development

Mature plants produce reproductive structures
- flowers
- seeds
- fruits
flowers and floral buds are reproductive shoots that develop when shoot apical (tip) meristems produce flower parts instead of new tissues and leaves
flowers are produced by determinate growth

Seed coats

Flower tissues enclose and protect tiny male and female gametophytes
- sperm in pollen fertilizes the egg, triggering ovules to develop into seed and flower parts to develop into fruit
fruits enclose seeds and function in seed dispersal
- Angiosperms

Meristems

Seedlings and mature plants produce new tissue from meristems
- cell factories
meristem is a region of undifferentiated cells that produce new tissue by cell division
A dormant meristem occurs at the shoot and root of seed embryos
- activate in seedlings
mature plants have shoot apical meristems (SAM) and root apical meristems (RAM)

Mature sporophyte develop from seedlings

photosynthesis powers the transformation of seedlings into mature plants
provides the ability to produce organic food
plants undergo both vegetative growth and reproductive development

Hierarchy of structures in a mature plant

Specialized cells
tissues
organs
organ systems
- branches, buds, flowers, seeds, fruits
root and shoot systems
plant (the organism itself)

Primary Growth

Elongation of plant organs
roots, stems, and leaves
Occurs in ALL plants
Produces primary tissues from apical meristems (SAM and RAM)

Primary Tissues

Primary xylem
- vascular/conducting tissue
- water and minerals
Primary phloem
- vascular/conducting tissue
- food and solutes
Epidermis
- dermal
  - Outter-most tissue
- protection
- holds water in plant
Support ground tissues
- Parenchyma
  - most abundant type
  - storage
    - water and food
  - part of cortex/pith
- Collenchyma
  - Protection/support of growing plant organs
  - cortex
- Sclerenchyma
  - protection/support of non-elongating organs
  - cortex

Secondary Growth

Expansion of plant organs
- lateral meristems
roots and stems only
- does not occur in leaves
noes not occur in all plants
Produces secondary tissues
- woody tissues

Major groups of Angiosperms

Eudicots

>240,000 species
all have primary growth
most have secondary growth
- for this class we are saying they all have secondary growth

Monocots

>60,000 species
all have primary growth
very few have secondary growth
- for this class we are saying that non have secondary growth
grasses, corn, tulips, lilies

Root system adaptations

Major functions

absorbing water and minerals
anchoring the plant in the soil
storing nutrients and water

Eudicots

Taproots

Monocots

fibrous roots

Three zones of root growth

Region of cell division
- RAM and root cap
- RAM contains cells that ar dividing
- Quiescent center keeps nearby cells undifferentiated
- Root cap embedded in mucigel
  - Mucigel is a slimy substance that covers the root cap of the roots of plants.
Region of elongation
- cells extend by uptake of water
Region of maturation
- root cell differentiation and tissue specialization
- identified by presence of root hair
  - water and mineral uptake

Root Internal Structure

Epidermis of mature roots encloses a cylinder of parenchyma called the root cortex
- One cell thick
- often rich in starch
  - functions as food storage
- many contain inter-cellular air spaces
Endodermis
- selective absorption of minerals
- one cell thick
Meristematic pericycle
- encloses root in vascular tissues
- provides lateral branches
woody roots produce primary vascular tissues followed by secondary vascular tissues

Eudicot root

Monocot Root

The shoot system

Stem and leaf adaptations

Shoots are modular with 4 parts

Stem node
- leaves or branches emerge
Internode
- stem between adjacent nodes
- elongation
Leaf
Axillary Meristem
- generate axillary buds
- can produce flowers or branches
  - Lateral shoots
- New branches bear SAM at their tips

Shoot Tip

Terminal bud
- at the end of each shoot
- includes the SAM and other parts
- scales

Leaf anatomy

Leaf adaptation

Leaf venation

Eudicot

Pinate (feathery)
Palmate (palm)
Netted
- provides more support for the leaves

Monocot

Parallel

Stem

Primary growth

mostly above ground organs,but some modified stems are blow ground
- Irish potato
  - underground stem

Eudicot Stem

ALC
Primary (elongation) and secondary (expansion) growth
vascular bundles (xylem and phloem) form a ring pattern
exhibit both a pith and a cortex
cambium ring produce cells
- provide secondary growth

Lateral Meristems

Produces secondary growth
2 lateral merstems
- both are rings that retain cell division properties and produce secondary tissues to the inside and outside of the cambium ring
Vascular cambium
- produces ring of secondary xylem (wood) to the inside and a ring of secondary phloem (inner bark) to the outside
Cork cambium
- Produces ring of periderm (outter bark) that replaces the epidermis and cortex for external protection

Secondary vascular tissue
- woody plants begin life with only primary vascular systems
  - produces secondary tissues and bark as they mature
- secondary xylem
  - wood
- Secondary phloem
  - inner part
- bark has both outer bark (mostly dead cork cells) and inner bark (secondary phloem)
Secondary growth
- begins late in first year of growth
- eudicot stem after 3 years of growth

Monocot stem

Primary growth (elongation)
vascular bundles (xylem and phloem) are scattered
lacks both pith and cortex

Comparison between Plant types

Leaves

Eudicot

net venation

Monocot

parallel venation

Roots

Eudicot

primary and secondary growth (mostly)
cortex
no pith
core of xylem in the root

Monocot

Primary growth only
both cortex and pith

Stems

Eudicot

primary and secondary growth (mostly)
vascular bundles in a ring pattern around cortex

Monocot

Primary growth only
vascular bundles scattered around
no pith or cortex

Primary Growth

Due to activities of Apical Meristems
- RAM and SAM
Results in production of primary growth

Secondary Growth

Due to activities of lateral maristems
- vascular and cork cambiums
Results in production of secondary tissues

Chapter 36

Overview of plant behavioral responses

Behavior is a response of an organism to an internal or external stimulus
types of plant behavior
- movement
  - bending,twisting, or rotating
    - nutation
  - rapid movement as in sensitive plants
    - response to touch
- growth
- seed germination
- seasonal production of reproductive structures
- defensive responses to attacks
  - thorns, spines, chemicals

Responses to internal and external stimuli

Internal

Internal biological clock
- circadium rhythms
chemical signals
- transcriptions factors and other proteins or hormones
- often interact with each other and external signals

External

light atmospheric gases (CO2 and water vapor) temperature, touch, wind, gravity, water, rocks, and soil minerals
Herbivors, pathogens, organic chemicals from neighboring plants, and beneficial or harmful organisms

Plant Behavior

Involves internal and external stimuli

tropism
- growth response that is dependent on a stimuli that occurs in a particular direction
Reception molecules
- located in plant cells
- sense stimuli and cause response

Phototropism

Growth response to light
light causes movement of hormone auxin away from said light
result in unequal distribution of auxin
- causing unequal cell elongation
positive tropism

Gravitropism

growth response to gravity
positive tropism
- roots
negative tropism
- shoots
columella cells in root cap/tip region sense gravity

Thigmotropism

Growth response to touch
roots
- columella cells cause roots to grow around obstacles

Regulation of plant growth

Hormones

chemical messengers that regulate plant growth
- most transported in phloem tissue
- all require an expenditure of energy on part of the plant (ATP) for transport
interact with external environmental stimuli

Hormones control

growth
seed germination
flowering
fruiting
shedding of leaves
color change of leaves

Hormones of two broad categories

growth inhibiting
- mostly fall/winter
- certain times of the year growth is not good
growth promoting
- mostly spring/summer

Auxins

first group of plants hormones to be described
growth promoting
produced in
- shoot tips, seeds, fruits, leaves, stem
- NOT in the roots

Effects of auxin

Promotes

cell elongation
shoot elongation
production of wood
fruit development

Inhibits

lateral bud development
absission (falling off) of leaves, flowers, fruits

Cytokinins

Originally detected in coconut "milk"
growth promoting
prodiced in
- seed, fruits, roots

Effects of Cytokinins

Promotes

cellular division
- named derived from Cytokenesis

Inhibits

senesence
- change of color due to breakdown of pigments

Gibberellins (giberellic acids)

many types
- >200
- more than any other group
growth promoting
found throughout the plant but concentrated in seeds

Effects of Gibberellins

Promotes

stem elongation by cell division and cell elongation

intake of water causes swelling and embryo hydration
embryo secretes gibberellins
gibberellins transported to cells of aleurone layer to secrete enzyme
(alpha-amaylase) for breakdown of endosperm (starchy stored food) to glucose
embryo will respire glucose to produce ATP
embryo is directing the timing of plant germination
Advantage seed plants

Brassinosteriods

growth promoting

Effects of Brassinosteriods

Promotes

cell expansion
shoot elongation
xylem tissue development
stress response

Inhibits

leaf abscission

Abscisic Acids (ABA)

Growth inhibiting
found in large quantities in seeds. mature leaves, and dormant buds

Effects of ABA

Promotes

senesence
production of storage molecules in seeds

Inhibits

cell elongation
alpha-amaylase production

Ethylene

growth inhibiting
actually a gas produced by incomplete metabolism
interacts with the 4 growth promoting hormones to determine cell size and shape

Effects of Ethylene

Promotes

fruit ripening
abscission of leaves, fruits, flowers

Seed germination

requires breaking of dormancy
- combination of internal and external factors

Internal

hormones
stored food
H2O absorption
embryo swelling

External

sunlight
temperature
longer day light
soil moisture

Generalized Seed

Seed coat(s)
as seed coat cracks
Radical comes out first
- then then shoot

Seedling

result of cellular reproduction and increase size
internal development
- cells>tissues>organs>organism

Chapter 37

Nutritional resources of plants

Essential elements

Play many roles in plant metabolism
often function as enzyme factors

Macronutrients

required in amounts of atleast 1g per 1kg of dry plant mass

Micronutrients

trace elements
required in amounts at or less than 0.1g per 1kg of dry plant mass

Limiting factors

resources that can limit plant growth
- too little or too much
carbon dioxide
water
other mineral nutrients

Chapter 38

Transport of materials in plants

Root system absorbs water and dissolved minerals from the soil
Shoot system takes CO2 from the atmosphere via stomata
Photosynthetic cells use these materials to produce organic compounds needed for growth and reproduction
long-distance transportation occurs withing the plant body using a continuous system of conducting materials
- Xylem
  - transport water and dissolved minerals
  - Only goes up
- Phloem
  - transports food and other solutes (hormones)
  - Goes up and down

Importance of water

Photosynthesis
support of plant organs
conduction
cell elongation
most chemical reactions
Average plant is 90% water
Solvent for most substances
- Solution
  - Solvent
  - Solute

Properties of water

Polar molecule
- neutral
Hydrogen bonding
Cohesiveness
Adhesiveness
Temperature Stabilizer
Transport medium
Best biological solvent
Occurs in all 3 forms of matter within earth's temperature range

Principles of movement

Bulk\Mass flow
- Mass movement of liquid cause by pressure and\or gravity
- Ex: leaching
  - movement of ion though soil to plant roots
- Faster than diffusion
Diffusion
- high concentration > low concentration
- Simple diffusion
  - Movement of molecules through a phospholipid bilayer down a concentration gradient
- Facilitated Diffusion
  - transport of molecules across a plasma membrane down a concentration gradient with the aid of membrane protiens
Osmosis"gatekeeper"
- Diffusion across a selectively permeable membrane in response differences in solute concentration
- simple diffusion of water does not occur rapidly enough for rapid expansion of plant cells
- Aquaporins
  - protein channels that allow facilitated diffusion of water

Tissue-level transport

trans-membrane transport
- export of material via membrane proteins, followed by import of the same substance by an adjacent cell
- Ex. Auxin transport aided by carrier protiens
Symplastic Transport
- Movement from cytosol of one cell to cytosol of another cell via plasmodesmata
  - Cytosol
    - Everything inside the cell wall
Apoplastic transport
- movement along cell walls and inter-cellular spaces
- Ex: water and disolved minerals

Cellular water content

water content of plant cells depends on osmosis, which depends on:
- Solute concentration
- Turgor preassure
  - hydrostatic pressure that increases as water enters plant cells
  - cell walls restrict the extent to which the cells can swell

- Turgid plant cell has cytosol full of water and plasma membrane pushes up against the cell wall
- Plasmolyzed cell has lost so much water that turgor pressure is lost and the plasma membrane no longer presses on the cell wall

Water potential

Potential energy of water
Water moves from highest to lowest water potential
- affected by
  - pressure
  - solute concentration
  - other factors (damage, temperature)
Concept used in 2 ways
- to understand the movement of water into and out of cells (cellular water potential)
- to understand the movement of water between entire plants and their enviroments

Water (and soil mineral) movement through the plant

Transpiration
- Evaporation of water from plant surfaces
- "cost" for the plant to live on land
- capable of pulling water up by bulk flow
- primary form of long distance water transportation in plants

Stomata
- Opening has 2 guard cells
  - control balance of CO2, O2, and H2O inside leaf

Xylem

Flowering plant xylem consists of 4 types of cells

Xylem parenchyma cells
Thick-walled supportive fibers
- may be alive or dead at maturity
vessel elements
- Speacilized water conducting cells and are always dead and empty of cytosol when mature
- Wide tubes
Tracheids
- tracheory elements
  - Rich in lignin which offers strength, durability, and water proofing
- Narrow tubes

Stomata

Plants produce a waxy cuticle to prevent water loss
stomata facilitate gas exchange
90% of water that evaporates from plants is lost through stomata
when stomata are open, O2 and water vapor are released and CO2 is taken up
controlled by guard cell pairs

Mechanisms of Guard cells

Daytime/sunlight
- CO2 is low in leaf
Guard cells "pump" in K (potassium)
- Changes solute concentration
H2O from xylem moves by osmosis onto guard cells
- cells become turgid
Guard cells swell and open stomata
- CO2 diffusion into leaf
"Pump" out K (potassium)
- H2O moves out by osmosis out of guard cells causing shrinking

Pumping
- Expenditure of ATP energy

Causes of water loss

Sunlight energy
- heats up leaf causing evaporating of H2O from mesophyll cells
- Causes a decrease in H2O concentration causing a "pull" of H2O
- This "pull" moves H2O though the "Transpiration stream"

Transpiration Stream

Soil H2O (and nutrients)
root epidermis
root cortex
endodermis
root xylem
stem xylem
leaf xylem
mesophyll
Vapor into atmosphere

Unidirectional movement
Only goes UP!

C-A-T Mechanism

Occurs once the stomata are open
Purely a physical process
"pull" of H2O one molecule at a time
unidirectional movement
Cohesion
- H2O molecules stick together
Adhesion
- H2O adheres to cellulose in cell walls
Tension
- "pull" due to H2O loss from mesophyll
NO ENERGY expended
Only energy is sunlight heating leaf

Solute movement in plants

Translocation
- movement of solutes in plants
food
- dissolved in H2O
- Moved in form of Sucrose
Goes form Source to Sink
- Site with excess of carbohydrate
- Site where the carbohydrate is stored or immediately needed
Bidirectional

Long-distance transport in phloem

Phloem transports sugars from where they are produced and\or stored to other sites where they are stored and/or needed
- Source > Sink
Primary Phloem
- Occurs in the vascular bundles of herbaceous plants
Secondary Phloem
- Occurs as the inner bark of woody plants

Phloem Structure

Phloem of flowering plants in composed of supporting fibers, parenchyma cells, sieve-tube elements, and adjacent companion cells (members)
Sieve-tube members (STM) are arranged end-to-end , and together with companion cells, form a system to transport soluble organic substances
- Sieve-tube members lose their nucleus and most of the cytoplasm to reduce obstruction to bulk flow
- phloem sap passes through sieve plate pores

Pressure Flow Hypothesis

At source

Companion cells "pump" sucrose into STM (STP expended)
As sucrose concentration increases in STM, water potential (concentration) decreases within STM
Adjacent Xylem has higher water potential than STM, H2O moves into STM by osmosis

Bulk flow of Sucrose
Higher Pressure > lower Pressure

At sink

Companion cells unload sucrose (ATP expended)
Sucrose converted into starch for storage in root cortex
Without sucrose, higher H2O potential in STM
H2O moves from STM to adjacent Xylem by osmosis

ATP spent only by companion cells at source (loading) and sink (unloading)
Bulk flow (pressure/potential differences) and osmosis (H2O potential\concentration differences)
- No energy Expended

Similarities Between Translocation and Transpiration

Both involve conduction
both involve physical properties of H2O

Translocation	Transpiration
Phloem Bidirectional Must expend ATP energy by plant	Xylem Unidirectional Sunlight energy (no expenditure by plant)

Chapter 39

Reproduction in plants

Most flowering plants display sexual reproduction
- Two gametes fuse to produce offspring with a unique combination of genes
They undergo Alternation of Generations
- Two multicellular life cycle stages
- diploid
  - Spore producing sporophyte
    - produces spores by meiosis
      - a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.
- haploid
  - Gamete producing gametophyte
    - produces gametes by mitosis
      - a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.
Egg is Female
Sperm is Male

Evolutionary Trends in the Plant Kingdom

Sporophyte has become larger, more complex
- Flowering plants
  - Sporophyte independent
  - Dependent gametophyte is only a few cells contained within flowers
Gametophyte has become smaller, less complex
- Moss
  - Sporophytes small and dependent on gametohyte (Dominant form)
Female
- 7 cells
Male
- 2-3 cells

Flower and Sexual Cycle

Flowers
- ONLY in angiosperms
- All sizes, shapes, colors, and aromas
Essential process of Sexual reproduction occurs within flowers
- Meiosis/cytokenesis
  - reduces chromosome number
- Syngamy (fertilization)
  - restores chromosome number

"Ideal" Flower

Uses highly modified leaves arranged in whorls (circular) at the tip of a highly modified stem
A flower is a highly modified determinate (short term) shoot system

Pedical, receptical, 4 sets of highly modified leaves are all 2N and part of the sporophyte generation
Pollen (sperm) and eggs of embryo sac are part of the 1N generation
Pedical
- flower stalk
Recepticle
- tip of modified stem with 4 whorls attached

Sexual Cycle

Male

Pollen formation
- occurs within the anther of stamen
Anther
- Bilobed with 2 pollen chambers per lobe

2N microspore mother cell
meiosis/cytokenesis
4 1N microspores
Each: mitosis/cytokenesis
unequal and incomplete
1N Generating cell
1N Tubecell

Male Gametophyte

Pollination

Transfer of pollen from the anther to the stigma
Self-pollination
- Transfer with the same flower or between flowers on the same plant
Cross-Pollination
- Transfer between flowers of other plants

Pollinating Agents

Mechanisms utilized for transfer of pollen

Wind
- small/lightweight pollen
Water
- Transfer with a few aquatic plants
Animals
- Majority of plants
- Utilized as a "trick and reward" system
- nectar, colors, and aromas to attract animals

Female

Ovule Development

Ovule
- future seed
Enclosed within the ovary of pistol (carpel)
One to many ovules per ovary
- ovary will become fruit
Ovule attached to central axis or to wall of hollow fruit
- always enclosed
- angiosperms
within ovule is 1 large 2N cell
- megaspore mother cell

2N megaspore mother cell
meisos/sytokenesis
4 1N Megaspores
3 degrade
2N Functional megaspore
Series of 3 mitosis/cytokenesis cycles
Incomplete and unqueal
7-celled embryo sac
8 nuclei

Female gametophyte

1N Functional megaspore
- 3 mitosis/cytokenesis divisions
One cell with 1 nucleus becomes 8 nuclei but only 7 cells

Embryo sac

8 nuclei, 7 cell structure
female gametophyte
3 antipodal cells (1N)
- opposite end from micropyle
1 central cell with 2 large 1N polar nuclei
2 Synergids (1N)
- Micropyle end on outside
1 egg (1N)
- Middle at micropyle end

Syngamy (fused gametes)

1N egg + 1N sperm = 2N zygote (single fertilized egg)
Pollen grain germination
- tube cells form pollen tube (delivers sperm)
- generative cell divides by mitosis/cytokenesis to produce 2 sperm

Pollen tube enters micropyle
- digests tube cell nucleus
Pollen tube enters one synergid
- releases it's content (sperm)
- synergid ruptures
- mycropyle closes

"Double fertilization" (double fusion)
- 1N egg +1N sperm = 2N zygote
- 1N sperm +2 1N polar nuclei = 3N primary endosperm cell

Post fertilization with ovule
2N zygote grows by mitosis/cytokenesis into 2N multicellular embryo
3N primary endosperm cell grows by mitosis/cytokenesis into 3N multicellular endosperm
- nutrient tissue for embryo

Ovule/ovary with 2N zygote mature/enlarges with sugars/H2O into a fruit (mature ovary) with enclosed seeds (mature ovules)
Seed dispersal (seeds enclosed withing a fruit)
agents
- wind
- water
- animals - majority

Seed germination

Seed with 2N embryo enters period of dormancy
dormancy broken by a combination of internal (hormones) and external factors (environmental)
radical (first root) emerges and grows down
shoot emerges and grows up