Biology 1110 Week 8

Front 1

Gas exchange and Transport in Plants

Back 1

yea

Front 2

Solute

Back 2

a solid material that is dissolved in a solvent

Front 3

Solvent

Back 3

a substance that the solute is dissolved in. (water)

Front 4

Solution

Back 4

a mixture of solvent and solute and is homogenous ( meaning the solute is fully dissolved and equally distributed in the solvent)

Front 5

Types of solute and solvent transport

Back 5

- Diffusion
- Facilitated diffusion
- Osmosis
- Active Transport

Front 6

Diffusion

Back 6

the movement of SOLUTES from an area of HIGH concentration of solutes to an area of LOW concentration of solutes

Front 7

Diffusion

Back 7

- does not require energy
- does not require a semipermeable membrane
- however, can and does occur across plasma membrane

Front 8

Facilitated diffusion

Back 8

- Passage mediated by proteins
- movement of molecules in the direction determined by their relative concentration inside and outside of the cell.

Front 9

Types of proteins that mediate the movement of solutes in facilitated diffusion

Back 9

- Carrier proteins
- Channel proteins

Front 10

Carrier Proteins

Back 10

- bind specific molecules to be transported on one side of the membrane

Front 11

Channel proteins

Back 11

- form open pores through the membrane, allowing the free diffusion of any molecule of the appropriate size and charge

Front 12

Osmosis

Back 12

- movement of solvent (usually water)
- Movement is through a SEMI-PERMEABLE MEMBRANE having the right properties
- movement is from the side with low solute (high solvent) concentration to and area of high solute (low solvent) concentration.

Front 13

Properties of semi-permeable membrane for Osmosis

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- permeable to water
- not permeable to solute

Front 14

Hypotonic solution

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- LOW concentration of solute
- HIGH concentration of solvent

Front 15

Hypertonic solution

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-High concentration of solute
- LOW concentration of solvent

Front 16

Isotonic solution

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Equal amount of solute and solvent

Front 17

Animal cell in a hypotonic solution

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- Lyses- (solution with high concentration of water goes to an area of low concentration of water (the cell) which overloads the cell with water, therefore, lyses the cell)

Front 18

Animal cell in a hypertonic solution

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- Shrivels- (water in cell which has a higher concentration of water moves to the area that have low concentration of water, shrinking the cell)

Front 19

Animal cell in an isotonic solution

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- Normal (equal rate of transfer of solute and solvent)

Front 20

Plant cell in a hypotonic solution

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- cell becomes TURGID

Front 21

Plant cell in a hypertonic solution

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- cell is PLASMOLYZED

Front 22

plant cell in an isotonic solution

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- Flaccid

Front 23

Active transport

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- movement of solute across a semipermeable membrane
- from an area of LOW SOLUTE concentration to an area of HIGH SOLUTE concentration
- Requires energy

Front 24

Active transport (picture)

Back 24

Front 25

Key adaptation of vascular plants for acquiring gases, sunlight, water, and minerals

Back 25

- Root hairs
- Stomata
- Lenticels
- Mycorrhyzae

Front 26

Root hairs

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- extend from root epidermal hairs
- Respiratory gases exchange with soil spaces
- provides and increased surface area for the absorption of water and minerals

Front 27

Root hair process of acquiring water and gases

Back 27

- water enters root hairs by osmosis
- water entry carries DISSOLVED GASES present in the soil
- diffusion of gases occur between air and soil spaces
- Dissolved gases are transported in the xylem, which also carries water and minerals to other plant parts

Front 28

Lenticels

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- Located on the bark of woody stems
- elevated dots or streaks
- Rupture of epidermis in stem caused by rapid growth of cell mass under epidermis
- rupture leaves spaces for gas diffusion

Front 29

Stomata

Back 29

- small openings on leaf surfaces
- Stomata allow for gas exchange

Front 30

Mycorrhyzae

Back 30

- mutualistic association of fungal hyphae with vascular plant roots
- provide a greater surface area for the absorption of water and minerals

Front 31

Plant adaptation for sunlight

Back 31

- Size of leaves
- The arrangement of leaves on a branch
- Leaf orientation
- branching from the stem

Front 32

Size of leaves

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- important to reduce evaporative water loss
- smaller leaves will have less water loss

Front 33

The arrangement of leaves on a branch

Back 33

- the angle of leaves
- can maximize exposure to light and reduce shading of lower leaves

Front 34

Leaf orientation

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- vertical or horizontal
- horizontal maximizes sunlight in low light conditions but may be prone to more damage from intense light

Front 35

Structure of a leaf

Back 35

- The ground tissue in a leaf, called the MESOPHYLL is sandwiched between the upper and lower epidermis
- (upper mesophyll) PALISADE MESOPHYLL
- (lower mesophyll) SPONGY MESOPHYLL - where gas exchange occurs

Front 36

Processes in leaves

Back 36

- Oxygen and carbon dioxide are the respiratory gases
- Gases enter and leave the leaf through the STOMATA
- O2 and CO2 diffuse within the SPONGY PARENCHYMA layer, then to the PALISADE LAYER where most photosynthesis takes place
- Vascular bundles bring water and minerals to the leaf and carry away sugars produced there

Front 37

Leaf structure picture

Back 37

Front 38

Stomata structure

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- located on leaf epidermis
- stomatal pore is flanked by two guard cells, which regulates its opening and closing

Front 39

3 cues believed to result in stomatal opening

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- the movement of K+ from surrounding epidermal cells into guard cells followed osmotically by water and increased turgidity
- The depletion of CO2 in the air spaces of the leaves
- A natural circadian rhythm which is seen if plants are kept in the dark continuously

Front 40

Mechanism if stomatal opening 1

Back 40

- structurally, the portion of the cell wall closer to the stomata is thicker than the outside
- stomata open due to the reversible active accumulation of K+ in guard cells from surrounding epidermal cells ( where there is higher concentration of solutes, water follows)

Front 41

Mechanism if stomatal opening 2

Back 41

- at dawn, blue light receptors are stimulated in the membrane of guard cells
- this in turn stimulates ATP- DRIVEN PROTON PUMPS
to pump out H+ ions into the epidermal cells
- This then drives the uptake of K+ ions from the surrounding epidermal cells into the guard cells
- water follows by osmosis and the guard cells become turgid

Front 42

Mechanism if stomatal opening 3

Back 42

- the uneven make up of the guard cell cell wall causes buckling and the creation of an opening
- closing of the guard cells occur when K+ are lost from the guard cells and water leaves the guard cells making them flaccid and closing stomata

Front 43

There are 2 types of vascular tissue in plants

Back 43

- xylem
- phloem

Front 44

Xylem has 2 types of conducting cells

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- tracheids
- vessel elements

Front 45

xylem's conducting cells...

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- conducts water and minerals from the roots to other parts of the plant
- the nuclei of these conducting cells are dead at maturity

Front 46

Xylem Composition

Mature xylem tissue contains:

Back 46

- vessel elements
- tracheids
- sclerenchyma
- parenchyma ( the only living cells in mature xylem tissue)

Front 47

In addition to transporting water and minerals, Xylem is also used for plant

Back 47

-support

Front 48

Composition of Phloem tissue

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- Sieve elements
- Companion cells
- also contains sclerenchyma and parenchyma

Front 49

Sieve elements

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- the nuclei of sieve elements break down at maturity and only the cytoplasm remains

Front 50

Companion cells

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- the cells retain their nuclei and their nuclei may help control sieve elements

Front 51

Function of phloem

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- transport of organic compounds (eg. carbohyrates and amino acids)
- may transport either direction (up or down)

Front 52

Mechanisms by which water and minerals enter plant roots

Water and minerals can travel through a plant by three routes

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- transmembrane route
- symplastic route
- apoplastic route

Front 53

Transmembrane route

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- out of one cell, across a cell wall, and into another cell

Front 54

Symplastic route

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- via the continuum of cytosol ( little pathways through cells)

Front 55

Apoplastic route

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- via the cell walls and extracellular spaces

Front 56

Absorption of water and minerals by root cells

Back 56

- most water and mineral absorption occur near root tips where epidermis is permeable to water and root hairs are located
- Root hairs account for much of the surface area of roots
- after soil sollution enters the roots, the extensive surface area of cortical cells membrane enhances uptake of water and selected minerals

Front 57

Transport of Water and Minerals into the Xylem

Back 57

- The endodermis is the innermost layer of cells in the root cortex
- surrounds the vascular cylinder; the last checkpoint for selective passage of minerals from the cortex into the vascular tissue
- water can cross the cortex via the symplast or apoplast
- the waxy Casparian strip of the endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder

Front 58

water absorption in plant roots picture

Back 58

Front 59

Mechanism of water and mineral movent
- two theories

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- root pressure
- transpiration-adhesion-cohesion

Front 60

Root pressure theory

Back 60

- the force required to push water up the xylem is due to the osmotic movement of water from the soil into the roots
- pushes xylem sap up the xylem, and when cut, xylem sap comes out the top
- unfortunately, the pressure exerted is only enough to lift xylem sap up to 2 meters

Front 61

transpiration-adhesion-cohesion theory

Back 61

- relies on cohesion of water and the process of transpiration
- water evaporates from a leaf (transpiration) via the stomata
- this causes water deficit at the leaves
- columns of water are pulled up the xylem by the cohesive forces of the water molecules
- this pull is transmitted throughout the entire plant
- transpirational pull is facilitated by COHESION of water molec. to each other and ADHESION of water molec. to cell walls
- therefore, transpiration supplies the pull

Front 62

Factors affecting transpiration

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- Available light
- Temperature
- Relative humidity
- Air movement
- Availability of water
- Atmospheric pressure

Front 63

Available light

Back 63

- increased rate of photosynthesis causes increased sugar levels leading eventually to opening of stomata and loss of water (increased transpiration)

Front 64

Temperature

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- higher temperatures leads to increased evaporation and increased transpiration

Front 65

Relative humidity

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- Increased humidity (high concentration of water in the atmosphere) leads to a decrease in transpiration

Front 66

Air movement

Back 66

- wind around the leaf increases transpiration

Front 67

Availability of water

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- if water is limited, guard cells will wilt and stomata will close decreasing transpiration

Front 68

Atmospheric pressure

Back 68

- lower pressure results in increased transpiration

Front 69

how the products of photosynthesis are be transported in vascular plants

Back 69

you'll see

Front 70

Phloem sap

Back 70

- an aqueous solution that is high in sucrose
- travels from sugar source to a sugar sink

Front 71

Sugar source

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- an organ that is a net producer of sugar, such as mature leaves

Front 72

Sugar sink

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- an organ that is a net consumer or storer of sugar, such as a tuber or bulb

Front 73

Transportation of phloem sap by diffusion is

Back 73

not adequate

Front 74

Products of photosynthesis are transported by

Back 74

Phloem

Front 75

2 theories on how phloem sap is transported

Back 75

- cytoplasmic streaming theory
- pressure or mass flow theory

Front 76

Cytoplasmic streaming theory

Back 76

- says that materials flow from one sieve element to another along a concentration gradient
- is moved within the sieve element rapidly from one end to the other by cytoplastic streaming
- no evidence to support this theory

Front 77

pressure or mass flow theory

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- involves changes in turgor pressure that allow a mass flowof wter and solute along a TURGOR PRESSURE GRADIENT in the sieve tubes

Front 78

pressure or mass flow theory 2

Back 78

- sugars transported into phloem cells have a high osmotic activity
- water follows into the sieve tubes raising turgor pressure
- neighboring sieve elements have LOWER TURGOR PRESSURE and therefore sugar and water will be forced into these sieve elements by turgor pressure
- when sugars reach metabolically active areas of the plant, SUGARS ARE REMOVED from the sieve tubes and turgor pressure drops as follows