Exam 2 - Notes
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
- female
- 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)
- cellular reproduction
- increase in cell size
- elongation
- increase in weight/mass
- Increase in number of cells
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
- dermal
- 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
- Parenchyma
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
- Irish potato
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)
- woody plants begin life with only primary vascular systems
- 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
- bending,twisting, or rotating
- growth
- seed germination
- seasonal production of reproductive structures
- defensive responses to attacks
- thorns, spines, chemicals
- movement
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
- Xylem
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
- Solution
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
- Cytosol
- Movement from cytosol of one cell to cytosol of another cell via plasmodesmata
- 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)
- affected by
- 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
- Opening has 2 guard cells
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
- tracheory elements
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 |
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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.
- produces spores by meiosis
- Spore producing sporophyte
- 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.
- produces gametes by mitosis
- Gamete producing gametophyte
- 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
- Flowering plants
- Gametophyte has become smaller, less complex
- Moss
- Sporophytes small and dependent on gametohyte (Dominant form)
- Moss
- 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
- Meiosis/cytokenesis
"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
-
- 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