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Flashcards in Plants Deck (76):
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Angiosperms are divided into 2 groups:

Dicots and monocots

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Two types of seed plants

Gymnosperms(conifers) and the Angiosperms(flow ring plants)

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Dicots:

2 cotyledons,

In 4s,5s,

Netted and organized in a circle

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Monocots

1 cotyledon,

Parallel,

3s

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3 Types of Plant Tissue

Ground tissues

Dermal tissues

Vascular tissues

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Ground tissues: Collenchyma

Cells which have thick but flexible cell walls, serve mechanical support functions.

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Ground tissue: Parenchyma

Most common, has thin walls, storage, photosynthesis, and secretion.

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Ground tissues: Sclerenchyma

Thicker walls than collencyma, also provide mechanical support functions.

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Dermal tissue
*Cuticle

Covers and protects the plant. It includes the EPIDERMIS and modified cells like guard cells, root hairs, and cells that produce a waxy cuticle.

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Vascular tissue: consists of 2 major kinds of tissues
*vascular bundles

Xylem and phloem. The two usually occur together to form VASCULAR BUNDLES.

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Two types of Xylem cells

Tracheids and Vessel elements.

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Xylem functions
*2 types of cells:
*Pits

The conduction of water and minerals. They travel up.

Have 2 types of cells:tracheids and vessel elements

Sometimes Xylem cells has PITS, or places where the secondary cell wall is absent.

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Xylem: tracheids

Tracheids, are long and tampered, water passes from one tracheid to another through pits on the overlapping tapered ends of cells.

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Vessel members(vessel elements)

Are generally wider, shorter, thinner, walled, and less tapered than tracheids.

Most angiosperms have both tracheids and vessel members.

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Xylem: Proferations

Literally holes between cells. Because of this, water movement through vessel members are more efficient than through tracheids.

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Phloem

Transports sugars.

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Phloem: companion cells

Companion cells are living parenchyma cells that lie adjacent to each sieve-tube member.

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Phloem: plasmodesmata

Maintain physiological support to the nuclei-lacking sieve-tube members.

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Phloem: Sieve-tube members(elements)

Living at maturity and lack nuclei/ribosomes.

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The seed consists of...

An embryo, a seed coat, and some kind of storage material.

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The seed: major storage material may be an:

Endosperm or cotyledons.

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The seed:dormant

After a seed reaches maturity, it remains dormant until specific environmental cues(like water or temperature) are encountered.

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The seed: Cotyledon

Seed leaf within the embryo of a seed.

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The seed: the embryo consists of 5 parts
1.epicotyl
2.Pumule
3.Hypocotyl
4.Radicle
5. Coleoptile

1.epicotyl- top portion of the embryo
2. Pumule- attached to the epicotyl(young leaf)
3. Hypocotyl- below the epicotyl
4. Radicle- develops below the hypocotyl. Develops into the root.
5. Coleoptile(in monocot)-surrounds and protects the epicotyl

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The seed: apical meristems
*Where are they found?

Responsible for vertical growth and found at root and shoot (apex) tips.

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The seed: zone of maturation

Where cells mature into xylem,phloem, parenchyma, or epidermal cells.

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The seed: root tip(root cap)

Protects the apical meristem behind it.

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The seed: Zone of Elongation

Newly formed cells absorb water and elongate.

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The Leaf: Guard Cells
What is the function?

Control the opening and closing of the STROMATA. Stromata are openings in the epidermis that allow gas exchange between the inside of the least and the external environment.

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The Leaf: Guard Cells
-stromata

Control the opening and closing of the STROMATA. Stromata are openings in the epidermis that allow gas exchange between the inside of the least and the external environment.

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The Leaf: Palisade Mesophyll

The inner part of the leaf. Equipped with numerous chloroplasts and large surface areas(specialized for photosynthesis.)

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The Leaf: Spongy Mesophyll

Spongy Mesophyll are loosely packed to allow diffusion of gases into and out of the cells. Made of parenchyma cells.

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The Leaf: Vascular Bundles
*What are they also called?
*Where is it located?

Also called veins. They are located in the Mesophyll and carry water and nutrients from the soil to the leaves and also carry sugar, the product of photosynthesis, from the leaves to the rest of the plants. Consists of Xylem and Phloem tissues.

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The Leaf: Stomates
*Turgid
*Flaccid

When guard cells absorb water(TURGID) they cause the Stomates to open.

When guard cells lose water and become FLACCID, the Stomates close

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2 pathways water is transported: Apoplast
*What type of cells does it consist of?

Apoplast- water moves through cell walls. Consists of the "non-living" portions of the cells.

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The Leaf: Symplast( plasmodesmata)

PLASMODESMATA- small tubes that connect the cytoplasm of adjacent cells.

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2 pathways in which water is transported: symplast
*What type of cells does it consist of?

Symplast- water moves from one cell to another through the symplast, or "living" part of the cells.

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Transport in Plants: Xylem

Xylem fluid is pushed UP by root pressure.

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Transport of Xylem: Root pressure/ GUTTATION

The osmotic force called ROOT PRESSURE, can be seen at GUTTATION, the formation of small droplets on the ends of leaves of grasses in the early morning.

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Cohesion-tension theory: Cohesion

Cohesion- the molecular attraction between like substances.

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Cohesion-tension theory: Transpiration
*Negative Pressure

The evaporation of water from plants, removes water from leaves, causing NEGATIVe PRESSURE,

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Asexual Reproduction

Plants can clone themselves or reproduce asexually by vegetative propagation.

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Transport of sugars: Translocation
*Source
*Sink

Translocation- movement of carbohydrates through phloem from a SOURCE(leaves), to a SINK, a site of carbohydrate utilization.

Translocation can be described as pressure-flow.

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Sexual Reproduction
*Stigma
*Micropyle
*Double Fertilization
*Seed-Fruit

Fertilization in a flower begins with pollination( one nucleus, and two sperm nuclei) lands on the STIGMA of the flower and the sperm enter the ovule through the MICROPYLE.

One sperm nucleus fertilizes the egg and becomes the EMBRYO(2n). The other two sperm nucleus fertilizes the two polar bodies and becomes the triploid(3n) endosperm.

This process is known as DOUBLE FERTILIZATION.

After fertilization, the ovule becomes the SEED and the ripened ovary becomes the FRUIT.

In monocots, food reserves remain in the endosperm.
The dicot lacks endosperm

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Alternation of Generations

Gametophyte(n)--->gametes(n) through mitosis--->(fertilization) Sporophyte(2n)---->(meiosis) Spores(n)---> spores(n)----->(mitosis) Gametophytes(n)

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Plant Hormones: Auxins or IAA

*Phototropism
*Apical Dominance

Responsible for PHOTOTROPISM(influences plant responses to light)

Enhance APICAL DOMINANCE - the preferential growth of a plant upward(toward the sun)

Response to GEOTROPISM(gravity)

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Plant Hormones: Cytokinins
*Senescence

Delay SENESCENCE(aging) by inhibiting protein breakdown. Florists spray cytokinins to keep them fresh.

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Plant Hormones: Gibberellins
*Bolting

A group of hormones that promote plant growth.

Induce BOLTING, the rapid growth of floral stalk. Bolting occurs in rice plants when a fungus that produces GA attacks the plant.

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Plant Hormones: Abscisic Acid (ABA)

Inhibits growth.

Promotes seed dormancy. Enables plants to withstand drought.

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Plant Hormones: Ethylene
*Apoptosis
*Leaf abscission

Promotes fruit ripening.

Facilitates APOPTOSIS: programmed cell death.

Promotes LEAF ABSCISSION- the leaf dies and falls from the plant.

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Long-day plants

Flower in the spring and early summer when daylight is INCREASING

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Photoperiodism
*Circadian Rhythms

The physiological response to the photoperiod, such as flowering.

Plants have a biological clock set to a 24-hour day, known as CIRCADIAN RHYTHMS.

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Short-day plant

Flower in late summer and early fall when daylight is DECREASING

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Day-neutral

Plants do not flower in response to daylight changes.

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Germination and Development
-Germination
Describe the process of this

Germination begins with imbibition(absorption) of water ==> Enzymes ===> respiration. Absorbed water causes seed to swell and seed coat to crack ==> growing tips of radical produce roots that anchor seedling ==> elongation of hypocotyl.

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Germination and Development

-Meristems
*Lateral Meristems
*Apical meristems

Are areas in plants where mitosis occurs, due to this cell division, it is also where growth occurs.

Lateral meristems - can be at tip of lateral growth in plant.
Apical meristems - are responsible for vertical growth and found at root and shoot(apex) tips.

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Primary Growth VS Secondary Growth
-2nd growth
- 2 lateral meristems
- cork cambium

Conifers & woody dicots undergo 2nd GROWTH in addition to 1st growth(extend length)

2nd Growth increase girth and is the origin of woody plany tissues; occurs at 2 lateral meristems

Cork Cambium- Protective material that lines outside of woody plant.

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Primary Structure of Roots

Cortex-

Makes up bulk of root, storage of starch, contain intercellular spaces, providing aeration of cells for respiration.

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Primary Structure of Roots

Endodermis
*Suberin
*Casparian Strip

Ring of tightly packed cells at inner most portion of cortex.
-A band of fatty material (SUBERIN) called CASPARIAN STRIP.
CASPARIAN STRIP creates water - impenetrable barrier b/w cells ==> All water passing through endodermis must pass through endodermal cells and not b/w cells ==> control movement of water.

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Primary Structure of Roots

Vascular Cylinder(stele)
*pericycle

Makes up tissues inside endodermis (phloem, xylem, pericycle)
Outer part consists of one/several layers if cells( PERICYLE- from which lateral root arise). Inside pericycle are vascular tissue.

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Primary Structure of Roots

Monocot
*pith

Groups of xylem and phloem alternate in a ring with the PITH in the middle.

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Primary Structure of Stems

-Epidermis
-Cortex
-Vascular cylinder consists of:

*Vascular cambium

Epidermis - Contains epidermal cells covered w waxy (fatty-cutin) which forms protective layer called CUTICLE.

Cortex: Ground tissue types that lies b/w epidermis and vascular cylinder.

Vascular cylinder: Consists of xylem, phloem, and pith. VASCULAR CAMBIUM(dicot) is single layer of cells b/w xylem(inside) and phloem(outside) may remain undifferentiated and later become vascular cambium.

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Secondary Structure of Stems and Roots

Wood
*SAPWOOD

Formed from xylem tissues at maturity(dead. only the recent ones remain active to transport water (SAPWOOD)

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Secondary Structure of Stems and Roots

-Annual Rings

Size of rings => rainfall history.
Number of rings ==> age of tree.

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Structure of the Leaf
- Epidermis
*Transpiration
*trichomes

Protective, covered w/ cuticle(made w cutlin wax)

Transpiration - water loss through evaporation
Trichomes - hair, scales, glands.

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Transport of Water:
Step 1
-Apoplast

Water move through cell walls and intercellular spaces from one to another without ever enter cells. This pathway is called APOPLAST(nonliving portion of cells)

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Transport of Water:
Step 2
-Symblast/plasmodesmata

Water move through cytoplasm of one cells to another SYMBLAST through PLASMODESMATA(smalls tubes that connect cytoplasm of cells)

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Transport of Water:

1.Osmosis
*Root pressure, guttation

Moves from soil through root and into xylem by gradient. This osmotic force (ROOT PRESSURE) can be seen as GUTTATION, formation of small droplets of sap(water and minerals) on ends of leaves in morning.

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Transport of Water:

2.-Capillary Action
-Adhesion/Meniscus

Rise of liquids in narrow tubes, contribute to movement of H20 up xylem; results from forces of ADHESION(molecular attraction b/w unlike substances) between H20 and tube => MENISCUS is formed at top of water column. No meniscus in active xylem.

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Transport of Water:

3. Cohesion-tension theory
*Transpiration-negative pressure
* Cohesion
* Bulk Flow

Most water movement is explained by this; major contributor

Transpiration 0 evaporation of water from plants, removes water from leaves => causing NEGATIVE PRESSURE(tension) to develop within leaves and xylem.

Cohesion: Attraction b/w like substances(water); within xylem cells behave as single, polymerlike molecule.

Bulk Flow: when a water molecule is lost from a leaf by transpiration. it pulls up behind an entire column of water molecules

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Control of Stomata

What happens when stomata are closed?
When stomata are open?

When stomata are closed => CO2 not available ==> Cannot photosynthesize

When stomata are open = > CO2 can enter leaf => photosynthesize but plant risks desiccation from transpiration.

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Control of Stomata

In high temperature what happens to guard cells? Cold temperature?

1. High temp => Close
2. Low CO2 inside=>open => photosynthesis

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Plant Responses to Stimuli:
-Tropism

Growth pattern in response to an environmental stimulus(due to plants not being able to move)

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Plant Responses to Stimuli:

- Phototropism

Response to light. Auxin is produced in apical meristem => move downward by active transport into zone of elongation => generate growth.
*Stem grows straight.

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Plant Responses to Stimuli:

Gravitropism
*What if stem is horizontal?
root is horizontal?

Response to gravity by stems and roots.

Stem is horizontal => auxin concentrates on lower side => stem bends upward.
If root is horizontal => Auxin produces moves up in root.

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Photoperiodism
-Photoperiod
-Circadian Rhythm
-Endogenous

Response of plants to changes in PHOTOPERIOD(relative length of daylight and night)

Plants maintain a CIRCADIAN RHYTHM - a clock that measures length of daylight and night)

Endogenous - internal clock that continues to keep time even if external cues are absent.