Steven Kuyper
BIOL 1010
Exam 3 Study Guide / Notes Review
Lecture 14: Plant Tissues
1) What is a Vascular Plant?
- A vascular plant consists of the following:
o Root System and a Shoot System
▪ Root System:
• Anchors the plant
• Absorbs water and ions(nutrients)
▪ Shoot System:
• Supports stem, leaves, and flowers
• Green in color for photosynthesis
2) What are the THREE Basic Tissue Systems?
- A) Dermal:
o Dermal is the outer protective layer
- B) Ground:
o This is the “inside”, squishy stuff
▪ Functions in storage, photosynthesis, and secretion
▪ Forms fibers to support and protect the plant
- C) Vascular:
o Moves fluids
▪ Conducts fluids and dissolved substances
***Each of these tissue types are found in the Root and Shoot Systems***
3) What are Meristems?
- Meristems are “plat stem cells”, as they give rise to the different types of tissues
o They are clumps of small cells with dense cytoplasm and large nuclei
o They act as stem cells do in animals
o One cell divides producing a differentiating cell and another that remains as a
meristematic (meristem cell)
▪ They divide through Mitosis.
▪ The Differentiated cells could become any of the three types of tissue (Dermal,
Vascular, and Ground)
▪ It will stop dividing once it decides what it will be.
-
1) Apical Meristem:
o In ALL Plants
o Located at the tips of stems and roots
▪ This is the extension of Shoot and Root Length
o Gives rise to PRIMARY TISSUE (Dermal, Ground, Vascular)
▪ A) Shoot Apical Meristem (SAM)
• Protection: Leaf Primordial
▪
B) Root Apical Meristem (RAM)
• Protection: Root Cap
o The root cap will continually get replaced as it gets damaged while
extending root in the ground.
o The Apical meristem may differentiate into 3 types of primary meristems:
▪ 1) Protoderm
• Forms Epidermis
▪ 2) Procambium
• Produces primary vascular tissue (Xylem and Phloem)
▪ 3) Ground Meristem
• Differentiates into Ground Tissue
-
2) Lateral Meristem
o ONLY found in Woody Plants (Trees, Bushes)
▪ Found in plants with Secondary growth
▪ Give rise to Secondary Tissues
▪ Woody plants have 2 Types of lateral meristems (‘bark”0
• 1) Cork Cambium
o Produces the outer Bark
• 2) Vascular Cambium
o Located under the Bark
o Produces secondary vascular tissue
▪ Secondary xylem (main component of bark)
▪ Secondary Phloem
▪ The vascular tissue is the move stuff from one side of the
tree to the other side.
4) What is Girdling?
- Girdling is the complete removal of a strip of bark from around a tree trunk
o Results in the death of the area above the girdle over time
- Removing the Bark – protective layer
o Taking this layer from the inside, which is important for transporting nutrients
▪ Everything above the girdle will die because the vasculature will be damaged,
especially the vertical/apical system and definitely the lateral system
o Below the girdling would not likely grow due to loss of photosynthesis capabilities
▪ Loss of access to upper part/leaves
5) What is Dermal in Plant cells?
- Dermal forms the epidermis
o The outer protective layer of a plant
▪ It is covered with a layer of Cutin (limits water loss (dehydration) from the plant
• Waxy, water repellent cuticle layer
o It contains special epidermal cells
▪ 1) Guard Cells
▪ 2) Trichomes
▪ 3) Root hairs
6) What are the Guard Cells in Dermal Cells?
- Guard Cells are paired sausage-shaped cells
o Swollen sausage filled with water
▪ The hole made is the Stomata when it is not swollen
▪ When Swollen, then the stoma is closed.
o Flank a stoma to regulate stoma opening (transpire) and closing (doesn’t want to lose
water)
o Stomata (Stoma – hole)
▪ Allows passage for:
• Oxygen
• Carbon Dioxide
• Water Vapor (releases)
7) What is Transpiration?
- Transpiration is the loss of water vapor from a plant
8) What are Trichomes in Epidermal Cells?
- Trichomes are the hairlike outgrowths of the epidermis
o They kept the leaf surfaces cool and reduced evaporation by shading the stomata
o Some are glandular, secreting substances that deter herbivory (biter tastes)
9) What are Root Hairs in the Dermal Cells?
- Root hairs are the extensions of the epidermal cells
o They increase the root surface area
o They increase the efficiency of absorption
▪ Helps absorb more to grow faster
10) What are Ground Tissues for Plant Tissues?
- Ground has three different Cell Types
o 1) Parenchyma
▪ They function in storage, photosynthesis, and secretion (ex: sap)
• Functions:
o Storage:
▪ Protein, Metabolic Waste
o Photosynthesis:
▪ Chlorenchyma contains chloroplasts
o Secretion:
▪ Resin (amber) – think mosquito Jurassic park
o 2) Collenchyma
▪ They provided support and protection
• More flexible
o EX) Cellery
• Tough and Flexible
• Provide support for the plant
• Allows bending without breaking
o 3) Sclerenchyma
▪ They provided support and protection,
• More rigid
• EX)Hemp, linen, resin
o They are tough, thick walls
o Cell Walls contain lignin for rigidity
o Types:
▪ A) Fibers: Long, slender cells grouped together in strands
▪ B) Sclerids: Variable in shape (can be a star)
11) What are Vascular Tissue for Plant Tissues?
- Xylem:
o Conduct water and dissolved minerals
▪ Directions: Root to Shoot
- Phloem:
o Conducts food and nutrients (Mainly sugars)
▪ Directions: Shoot to everywhere else.
12) What are Root Tissues for Plant Tissues?
- Root Regions:
o Root Cap
o Zone of Cell Division
o Zone of Elongation
o Zone of Maturation
13) Describe the Parts of the Root
- Root Cap:
o Composed of:
▪ A) Inner Columella Cells
• Look like columns
• Contain amyloplast
o Amyloplasts is an organelle with starch grain that collects on the
side of the cell facing the pull of gravity
▪ Helps plants decide where root to grow down toward
gravity.
▪ B) Outer, lateral root cap cells
• Continuously replenished by apical meristem.
-
Zone of Cell Division
o Center of Root Tip
o Site of Apical Meristem
o Cells divide producing daughter cells of apical meristem
-
Zone of Elongation
o Functions in Root lengthening
o Cells become longer than wide
-
Zone of Maturation
o Cells from elongation zone differentiate (Dermal, ground, vascular)
o Root hairs present
14) What are some Modified Roots?
- Prop Roots: Keep the plant upright (corn)
- Aerial Roots: obtain water from the air (orchid)
- Pneumatophores: Facilitate oxygen uptake in swamps or wetlands (Mangroves)
15) What are Stems?
- Stems function is to carry leaves and flowers and support the plant’s weight.
o 1) External stem structure
▪ Node – Region of area of leaf attachment to stem
▪ Internode- portion of stem between two nodes
▪ Leaf• Flattened blade (part of lead)
• Petiole- (stalk of leaf)
▪ Axillary Bud• Produced at each axil (between petiole and stem)
• Product of shoot apical meristem
▪ Terminal Bud- Extends the shoot during growing season.
DRAW
o 2) Internal Stem Structure
▪ Monocot vs Dicot (Eudicot)
• Monocot
▪ Vascular bundles (tissue) are scattered
▪ Viens on leaves are parallel pattern
o Dicot (Eudicot)
▪ Vascular Tissue is arranged in a ring
▪ Vein on leaves are in a branch pattern
o 3) Modified Stems
▪ 1) Tubers- Swollen tips stolon that contain carbohydrates
▪ 2) Tendrils – Twin around supports and aid climbing
▪ 3) Cladophylls – flattened photosynthetic stems resembling leaves
***Plants want to cover other plants so they can’t get sunlight (survival of the fittest)
16) What are Leaves?
- Leaves function is the principle site of photosynthesis
o Is the extension of shoot apical meristem
▪ 1) External Leaf Structure
• A) Veinso Consist of BOTH Xylem and Phloem
o Distributed throughout the leaf
▪ Eudicot = network
▪ Monocot = Parallel
▪
2) Modified Leaves
• Hot and Dry Environments
• Don’t want regular leaves because of water loss
o Spines
▪ Cactus Spines are LEAVES!
▪ Reduces water loss
▪ May deter predators
o The stem of the cactus functions as normal leaf does →
Photosynthesis
Lecture 15: Plant Reproduction and Development Part 1:
1) What are Angiosperms?
- Angiosperms are flowering plants
o They are characterized by:
▪ Presence of flowers
▪ Enclosed seed within an ovary (ex: fruit)
o Angiosperm
▪ Flowering plant (has seed)
o Gymnosperm
▪ Nonflowering plant
2) What is Angiosperm Maturation?
- It is Phase Change
o When the plant is sufficiently mature to be able to respond to environmental cues for
flowering.
o Juvenile -----Phase Change --→ Adult -----Temp &/or Light (Flower Promo/inhibit---|>
flowering
3) Which meristem produces flowers?
- The Shoot Apical Meristem (SAM)
4) What are the pathways to Making flowers?
- Four genetically regulated pathways to flowering have been identified:
o 1) The light dependent pathway
o 2) The temperature dependent pathway
o 3) The gibberellin dependent pathway
o The autonomous pathway (NOT DISCUSSED)
5) The Light Dependent Pathway
- The light Dependent Pathway for making flowers is called Photoperiodic
o This really depends on how much daylight is present
o Different plants flower in different seasons (ex: xmas cactus)
▪ Short Day Plants:
• Flowers when daylight is shorter than a critical length
▪ Long Day Plants:
• Flowers when daylight is longer than critical length
▪ Day Neutral Plant:
• Plant is not influenced by day length
• Flowers when plant is mature enough, regardless of day length
o Think of tropical plants at the equator (but need consistent light)
o Equator is where photoperiod doesn’t vary with season on Earth.
6) What are the advantages of photoperiodic control of Flowering (Light Dependent Pathway)
- 1) Flowering plants flower when the environmental conditions are optimal.
- 2) Flowers when pollinators are present.
- 3) Flowering during seasons that minimize competition with other plants.
o The flowers compete for Pollinators, nutrients, and light
- 4) It is used by the floral industry to control flowering for business
7) The Temperature Dependent Pathway
- Vernalization:
o This is the requirement for cold to induce flowering
▪ Put a plant in cold for a period of time, then transition to warm (Usually over a
period of months ( winter to spring)
• Know the image. (51 days for wheat to flower)
8) Gibberellin Dependent Pathway
- Gibberellin stimulates stem elongation, germination, and flowering
o Gibberellin is a plant hormone.
▪ Germination: Seed develops into a baby plant
9) What occurs during phase change in an angiosperm?
- The plant becomes capable of making flowers.
Flower Structure and Evolution
10) What is the function of a flower?
- It’s function is to house the reproductive organs of the plant.
o Sperm contained within pollen
o Ovules contained within the ovary
11) What are the different types of Flowers
- Monoecious:
o Plant flowers with both male and female structures present at the same time.
- Dioecious:
o Plant flowers with separate male and female structures on DIFFERENT plants
- Dichogamous:
o Plant flower with either only Male of Female structures.
▪ One plant that develops at separate times.
12) What is the function of the flower petals?
- To attract pollinators. They act as Bullseys, target points as pollinators ee in UV light so they
see colors that we don’t
Draw picture of Dioecious plant and its parts (Definitions)
13) What is Angiosperm Maturation?
- Plants mature from juvenile (embryo) to plant body and then they can produce flowers
- Diploid plant produces haploid gametes.
14) What is Flower Gamete Production?
- Flower gamete production occurs through alternation of generations
o Diploid sporophyte (Adult Plant) → haploid gametophyte (Gametes: egg, sperm)
▪ Male Gametophyte:
• Pollen Grains
▪ Female Gametophyte:
• Embryo Sac
15) What is the process of Flower Gamete Production (Pollen Vs Embryo Sac)
a. Pollen
o 1) Microspore Mother Cells (2n = diploid)
o 2) Via Meiosis, the mother cell makes Microspores (1n = Haploid)
o 3) Microspores, through mitosis, become pollen grain
▪ 4) In the pollen grain, there is a Generative Cell and a Tube cell
• Generative cell produces 2 sperm cells
• One tube Cell that makes the pollen tube
b. Embryo Sac
o 1) The ovule house the Megaspore Mother Cell (2n = Diploid)
o 2) Via meiosis, the megaspore mother cell produces four megaspores (1n = haploid)
o 3) Only ONE megaspore survives to be the embryo sac
o Becomes egg through mitosis
16) What is Pollination?
- Pollination is the movement of pollen from the Anthers to the Stigma
o This may occur by
▪ Wind, insects and animals
▪ Of by the Same Flower or Different Flower
▪ 1) Self Pollination:
• Pollination on the same flower
▪ 2) Cross-Pollination:
• Pollination from one flower to another
17) Explain Pollination via the WIND
- Wind is PASSIVE pollination (So no energy input by the plant0
o The plant that uses this lacks fancy flowers, scents, or nectar
o Wind pollinated plants that live close together to increase the chances of pollination
o Pollen travels less that 100m (short distance)
18) Explain Pollination via Insects:
- Bees are the most common insect pollinator
- Bees typically visit yellow or Blue flowers
o This is because they see in UV light
- Many flowers have stripes or lines of dots that indicate the location of nectar
o Think of it this way: the flower has evolved to be able to show where the bee should go,
like a target zone or bullseye.
19) Explain Pollination via Animals:
- Some rodents, bats, or even birds can pollinate flowers,
o They may co-evolve with certain flowers so that they can pollinate them
o Ex: Hummingbird long beak perfect for long/deep flowers
20) Outcrossing vs Self-Pollination
a) Outcrossing
- Favored in variable environments (Wildfires, drought, high and cold temps)
o Places where environment is ever changing
- Plants have high genetic diversity due to cross pollination
- Need pollinators/wind
o They spend more energy attracting pollinators
o Plants found close together to allow for wind pollination
b) Self-Pollination
- Favored in Stable (unchanging) environments
o Always the same, not stressful for the plant
- Plants are uniform (less diversity) but the plants are very well adapted to their habitat
o (This however could be detrimental if something unexpected happens because of the
lack of diversity)
- The locations where pollinators are scarce
- Plant does not spend energy on pollinators
21) What is the process of Fertilization
- 1) The pollen lands on the Stigma and grows pollen tube from the Tube Cell
- 2) Tube Pierces the style and grows until it reaches the ovule
- 3) The Generative cell produces TWO sperm that travel down the Pollen Tube
- 4) 2 Sperm enter the ovule
o Double Fertilization
- 5) 1 sperm joins the egg forming Zygote (2n = Diploid)
- 6) 1 Sperm joins TWO polar nuclei forming Endosperm
o (3n) = Triploid
▪ Endosperm is the food supply for the embryo
- 7) Embryo develops into seed
22) What is the Polar Nuclei?
- Polar Nuclei are Clusters of DNA
o Two of these join with 1 sperm to create Endosperm
▪ 1 Polar Nuclei (1n)
▪ 1 Polar Nuclei (1n)
▪ 1 Sperm (1n)
▪ = Endosperm (3n)
23) Draw Embryo Development (And List Steps)
24) What are Seeds?
- Seeds protect delicate embryo inside
- They allow the embryo to be dormant for long periods until conditions are ideal
- Embryo development is STOPPED soon after meristems and cotyledons are formed
- The Seed Coat
o Seed coat encloses the seed (embryo) with its stored food
o This allows a seed to survive in harsh environments
25) What is the Svalbard Seed Vault?
- This is where seeds from all known plants in the world stored near Greenland
o Underground controlled Room at -18 Celsius
o Each box hold 500 seed packed (pack holds 5000 seeds) and each vault holds 100s of
boxes
o Just in case we destroy ourselves, they can “rebuild” hopefully
26) Why are Seeds Important?
- 1) Dormancy:
o The Seed/plant stops all metabolic process
o Advantages: Under unfavorable conditions, the embryo can postpone development
until conditions improve
▪ Unfavorable conditions (Drought, High/Cold temp, lack of nutrients)
- 2) Protection
o The seed coat protects the delicate plant inside
- 3) Food
o Inside the seed, the embryo has nutrients (endosperm) that it will use until it can create
its own food
- 4) Dispersal
o Facilitate spreading of seeds to new habitats.
27) What are specialized Seeds?
- Some seeds are adapted to improve survival:
o 1) They may germinate ONLY when certain conditions arise
▪ EX: Fires – pinecones need fire to burn off the sap so that the seeds may emerge
o 2) They may germinate after passing through the gut of an animal
▪ Ex: Certain coffees -0 The enzymes in the gut will break down coffee outerseed
coat to allow the seed to emerge
o 3) They may germinate when seed coat is washed of inhibitory chemicals by water
▪ Need Rain to remove these chemicals
• Rain would also signify to the plant/seed that rain has begun
28) Explain the BEGINNING of Germination:
- Germination – The emergence of the first root (RADICLE) through the seed coat.
- Germination is triggered by:
o Water
o Oxygen
- Metabolism will resume
o This is because metabolism was paused during dormancy
- Water helps to break the seed coat.
29) What are the Signals for Germination?
- Signals for Germination include:
o Light
▪ Necessary for photosynthesis
o Temperature
▪ Warm temperature promotes germination
o Hormones
▪ Think of Gibberellin (grape ex)
- Many seeds must be Stratified
o Stratified means Held are low temperatures before germinating.
▪ For Seeds
• Different from Vernalization because that is for a plant that has already
passed the seed stage and is preparing to flower.
30) Germination and Energy
- Germination required energy
o Strach, proteins, fats
- Energy is stored in the seed in the:
o Cotyledon
▪ Relies on the Cotyledon for photosynthesis
o Endosperm
31) So how are Fruits relevant to seed?
- Fruits are Mature Ovaries
o The fruits are an adaptation that allow for seed dispersal
▪ Fruits (Carpel) develop from the Ovary Wall (pericarp) into 3 layers
• 1) Exocarp - skin
• 2) Mesocarp - flesh
• 3) Endocarp – pit/seed
▪ The Pericarp is all three tissue parts of fruit that develop from the ovary
32) What are different methods of Fruit Dispersal?
- Fleshy Fruit
- Sticky or Spiny Fruit
- Parachute Shaped (dandelions)
- Water impermeable (Coconut)
- Wings of Maples, elms, ashe tree seeds disperse in wind (Helicopter helicopteerrr)
33) What are the Plants Life Spans?
- 1) Perennial –
o Grow, reproduce/flower yearly
o Trees and Shrubs can be:
▪ A) Deciduous:
• All leaves fall at one particular time of the year
▪ B) Evergreen
• Leaves drop throughout the year and never appear completely bare
- 2) Annual
o Grow, reproduce and die in a single year
- 3) Biennial
o Grow, reproduce, and die after 2 years
- 4) goes on and on…
LECTURE 16: Plant Transport
How does Water move from the roots to the rest of the plant with a physical pump??
-
Water Transport:
o Roots – Water absorbed by roots
o Xylem – Water travels up through plant
o Pant Body
o Exits at Stoma
▪ Water vapor lost from leaf pores in transpiration
1) How does water get into the plant cell?
- Water enters a plant
o Across the aquaporins
▪ Water enters the central vacuole across the Tonoplast
• Tonoplasts (membrane, has aquaporins)
2) What is water transport – Water Potential? (Write it out – and Draw example)
3) In water transport – What is Turgid and Plasmolysis?
- Turgid:
o Water enters a plant cell and the cell expands/swells
o Normal, happy plant
▪ Water filled in the central vacuole
• Needs to stay turgid to keep photosynthesis effective (perky)
•
-
Since the Central Vacuole is full of water, the plasma membrane pushed
up against the cell wall, that’s why the plant is standing up right.
Plasmolysis:
o Water leaves a plant cell
o Cell membrane pulls away from the Cell Wall
o Volume of the cell shrinks
o Sad, wilted plant.
▪ Central vacuole is not full of water.
4) Why don’t the cells lyse?
- The cell wall is there so that it doesn’t explode/burst due to water (acts as barrier)
Xylem and Phloem Transport
5) What is Xylem Transport (Draw and Explain)
6) What is Phloem Transport?
a. What is Translocation?
o Translocation:
▪ The movement of Carbohydrates/sugars made in the leads to the rest of the
plant.
o Sucrose moves both up and down phloem!
b. What is Pressure -Flow Hypothesis?
o Pressure-Flow hypothesis describes how the carbohydrates move through the phloem
▪ Phloem flow is from a Source (leaves) to a Sink (plant body) where carbohydrates
are used.
c. Explain Plant Transport – Source
o Phloem Loading:
▪ This is when sucrose enters the phloem at the source by Active Transport of
sucrose across the membrane
• This requires ATP
o Water follows into sieve tube from Xylem by osmosis
o Turgor pressure in Phloem increases
▪ Turgor Pressure is the pressure exerted by water inside the plant cell against the
cell wall.
d. Explain Phloem Transport – Sink
o At sink, sucrose is actively removed (unloaded) from the sieve tube
▪ Requires ATP
o Water follows passively out of phloem to xylem
o Turgor pressure drops at sink
o Difference in pressure from source to sink results in fluid flow.
Draw and List Stems of Phloem Transport
LECTURE 17: Plant Nutrition
1) What is Soil?
- Soil is composed of the following:
o Minerals
o Organic Material
o Water
o Air
▪ Provides O2 for plant metabolism
o Microorganisms
▪ Break down and recycle organic debris.
-
-
*** A Balance of Water and Air in soil pores is important for root and plant growth
o You don’t want to overwater
▪ Too much water damages the roots and does not allow air to be present
• Root can get moldy and die.
Plants usually anchored in soil
o Soil does have airpockets.
2) How does the pH affect soil?
- The pH of Soil can influence plant growth
o Acidic soil can stunt growth
▪ The acidity actually breaks down the soil and the toxins can inhibit growth
▪ Toxic minerals could be things like metals
- The best growth would be with neutral pH
- Soil pH can release toxic minerals from rocks into soil that can harm plants or stunt growth.
3) How does Salt affect soil?
- The accumulation of Salt (Na and Cl) in soil will decrease water potential
o This results in loss of turgor in plants
▪ Turgor = turgid (stiff, full of water)
o The salinity can decrease plant growth
▪ As water potential in soil would be too low, drawing the water out of the plant.
4) What are Plant Nurtitional Strategies?
- Plants require ammonia (NH3) or Nitrate (NO3-) to build amino acids
- Atmospheric nitrogen is N2 gas
o Plants are unable to convert N2 gas to NH3
o As such there a Three Nutritional Strategies:
▪ 1) Symbiotic Bacteria
▪ 2) Mycorrhizal fungi
▪ 3) Carnivory
5) Explain Bacteria as a Nutritional Strategy for Plants:
- Bacteria can be house within specialized plant tissue called a Nodule
o A Nodule:
▪ A specialized swelling in the root of a plant that has symbiotic, nitrogen fixing
bacteria.
o The bacteria can provide nitrogen to the plant by nitrogen fixation.
▪ The chemical process of converting N2 gas to organic compounds by
microorganisms.
o Commonly occurs in legumes (beans)
6) Explain Mycorrhizal fungi as a Nutritional Strategy for plants:
- Plant roots and soil fungi form an association called mycorrhizae
o Usually common in vascular plants
o Mycorrhizae increase SA for nutrient uptake in roots
o Mycorrhizae allows phosphate and some micronutrient uptake by plant
▪ Basically, it works in tandem with the roots
▪ “root like hairs” covering more ground to gain more nutrients efficiently.
7) Explain Carnivory as a Nutritional Strategy for Plants:
- Carnivorous plants digest insects and small animals to gain nitrogen.
o These types of plants usually occur in habitates that lack organic nitrogen
▪ Nitrogen poor habitates such as Swamps
o The plant secretes a digestive enzyme to break down the prey
▪ In the Pitcher plants, the hairs are getting in the way
• They allow the prey to go down, but they can’t get back up
▪ With the Venus Fly Trap, there are three “hairs”, trichomes, and when two get
touched, the leaf closes around its prey.
8) What is Phytoremediation?
- Phytoremediation is the use of plants to concentrate or break down pollutants from soil
o Phytodegradation:
▪ Contaminant is taken up from soil and broken down
• Metabolizes the toxins
o Phytovolatilization:
▪ Contaminant is taken up from soil and released through stomata
• Metabolizes into something less toxic and released via stomata into the
air
o Phytoaccumulation:
▪ Contaminant is taken up from the soil and concentrated in shoots
• These Plants are later harvested
o Does not metabolize
▪ Harvested and thrown away (usually bc of Radiation)
9) How does Phytoremediation help with Radiation?
- In the past, we have used Sunflowers
o Sunflowers can decontaminate soil after radioactive events following nuclear disasters
- Sunflowers can extract and store contaminants in their stems and leaves
o Then they need to be destroyed afterwards (and thrown away)
- This method was used after Chernobyl and Fukushima power plant disasters.
LECTURE 18: Plant Defenses
1) What are some threats that Plants may face as they are immobile?
- Threats:
o 1) Environmental factors (ABIOTIC)
▪ Weather (drought)
▪ Fire
o 2) Parasites and Predators (BIOTIC)
▪ Viruses
▪ Bacteria
▪ Nematodes (worms)
▪ Fungi
▪ Animals
▪ Other Plants
2) What are the Plant Defenses – Dermal Tissue:
- Exterior:
o Wax and cutin- this protects the plant from water loss
o Trichomes
▪ The glandular bulbs on top of the trichomes can be bitter
o Bark
o Thorns
▪ ***These last three protect from Herbivorous predators***
3) What are the Plant Defenses – Chemicals?
- Plants are filled with toxins that can kill or make herbivores ill.
- Secondary Metabolite
o Chemicals produced by plants via metabolic pathways that are NOT used for normal
growth, development, or reproduction
▪ Not used in metabolism
• Rather for deterring predators (herbivores)
o Chemicals such as:
▪ Caffeine
• Trying to keep you sick. Too much makes you jittery,
the runs, etc.
▪ Nicotine
▪ Cocaine
▪ Even capsaicin (spicy)
4) What about Plant Toxins and Humans?
- Throughout history, humans have been unintentionally poisoned by plant toxin
o Ricin:
▪ Found in Castor Bean endosperm
▪
▪
6x more lethal than cyanide, 2x more lethal than cobra venom
Ricin in endosperm as Ricin A and Ricin B bound together as Proricin
• When that bond is Cleaved
o This makes Ricin A the toxic one
o Ricin B does nothing on its own.
▪ Ricin A inhibits Ribosomes, so inactivates rRNA preventing
mRNA translation.
▪ Kills within a few days, symptoms are like the flu.
5) What are some Secondary Metabolites that you should know?
- Cassava:
o Makes Cyanide.
o Cassava is a modified Tubor
▪ The outside skin is what has the chemical and it can be consumed but you NEED
to make sure it is VERY clean
-
Soybean:
o Acts as an Estrogen Mimic (Phytoestrogen – plant based estrogen)
▪ In some men, they may lactate if too much Soy is consumed
-
Pacific Yew (Taxol)
o Taxol found in the Pacific Yew
o Used as an Anticancer drug – still used in most chemotherapy today
-
Quinine
o Found in Quinine Bark
o Used as an Antimalaria drug
▪ Could be used in a Gin n Tonic as some Tonic Water has Quinine added to it
-
Morphine
o Found in Opium Poppy (flower)
▪ It is a Narcotic Pain Killed
▪ Sometimes you may fail a drug test even with Poppy muffins.
6) How do animals protect plants?
- Some plants and animals have coevolved to benefit each other (mutualism)(symbiotic)
- Ex: Acacia Tree and Stinging Ants
o The Stinging ants live on acacia tree in hollow thorns
o They sting other insects, small mammals and even other plants that eat or invade the
plant
o The Ants are then provided with sugar made by the plant
▪ Suagar/nectar released to the ant as a reward for protecting it.
-
Parasitoid wasp, caterpillar, and leaves
o 1) the caterpillar eats leaf
o 2) leaf releases a volatile chemical into the air
o 3) chemical attracts wasp
o 4) parasitoid wasp lays eggs in body of caterpillar
o 5) eggs hatch and then kill and eat caterpillar
LECTURE 19: Plant Environmental Responses & Hormones
1) What is Phototropism?
- Tropisms are directional growth responses
o Phototropisms involve shoots growing towards the light
▪ Light triggered development
o Positive Phototropism:
▪ Plants growing toward the light source
• (+) in shoots
o Positive Tropisms – growing toward specific trigger
• (-) in roots
o Negative Tropisms – growing away from trigger
- This is an adaptive response giving plants more light exposure for photosynthesis
2) What is Gravitropism?
- This is the response of a plant to the gravitational field of the earth
- Shoots exhibit Negative Gravitropism (growth against gravity)
- Roots have a positive gravitropic response (toward gravity)
o Plants grown in space exhibit wavy and wiggly root pattern
3) What is Thigmotropism?
- Thigmotropism
o is Turning or bending of a plant in response to touch or stimulus
▪ Plant response to touch
- Thigmomorphogenesis:
o Permanent plant structural change in response to continuous mechanical stress
▪ Ex: Wind blowing on Tree in windy area
-
Thigmonastic Response:
o Plant response to touch that is independent of direction
▪ Touch of those triggers (ex: fly trap – touch of trichomes)
4) What is plant Dormancy?
- Dormancy is the result in cessation of growth
o Stopping all metabolic processes
- Dormancy provides a survival advantage when environmental conditions are unfavorable
- Often begins with abscission
o Abscission = dropping of leaves
***when you prune a plant, you are helping the plant save energy , to help it become dormant during its
designated season.***
5) What is Abscission?
- Abscission involves the formation of the separation layer at the abscission zone
o Abscission zone is where the petioles’ base for leaves on Deciduous trees.
▪ Results in seasonal dropping of leaves
Plant Hormones
6) What is the Plant Hormone – Auxin
- Auxin
o Auxin is the hormone that accumulates on the side of the plant cell wall and promotes
cell elongation
▪ Results in plant bending toward the light.
o The plant cells that are in the shade have more Auxin and grow faster than cells on the
Lighted side
▪ This causes the plant to bend toward the light.
• As such, the cells on the shaded side are bigger
o **The Amount of Auxin will accumulate opposite of light***
-
The phototropins are more active on the Light Side, while they are less active on the Shade side
o This allows more Auxin flowing down the Shady side
7) What is the Plant Hormone – Ethylene
- Ethylene suppresses stem and root elongation, but increases fruit ripening.
o Tomato Example:
▪ Wildtype tomatoes can synthesize ethylene and naturally ripen on the vine
o Transgenetic tomatoes have ethylene gene removed
▪ Cannot synthesize ethylene naturally
• They are harvested green and then ethylene applied in warehouse to
control ripening
8) Plant Hormone Summary:
- 1) Auxin
o Promotions of stem elongation and growth
o Formation of adventitious roots
o Inhibition of abscission
- 2) Gibberellin
o Promotes stem elongation
o Stimulation of enzyme production in germinating seeds
- 3) Ethylene
o Control leaf, flower and fruit abscission
o Promotes fruit rippening