Module 3.3 Transplant In Plants Flashcards
Why do plants need a transport system
Plants are multicellular organism
They have a high metabolic rate
Plants have a small surface area to volume ration
Rate of diffusion would be slow because of large distance
Can you draw the cross section of a vascular section in the root
Can you draw cross section of vascular bundle in a stem
Can you draw the cross section of a vascular bundle in a leaf
What is the function of the xylem vessels
To transport water up the plant
Supports the plants (lignin)
What the the function of the phloem
To transport assimilates from source to sink
What features does the xylem have
It is hollow,
there are no end walls,
contains dead cells,
contains lignin,
has pits
Also has a ring or spiral structure for flexibility
Also has xylem parenchyma which stores food also contains tanin which prevents herbivores from eating the xylem
State the function of lignin in the xylem and explain why it’s important
It also helps strength the cell
How?
prevents walls from collapsing when there is low turgor pressure.
Spiral band of lignin is flexible
Also helps reduce loss of water
State the function of bordered pits
Reason
is to allow water to go out of the xylem
Why?
so tissues can be supplied with water.
What substances are transported in the xylem vessel
Water and minerals
What three parts of phloem tissue
Phloem paracheyma
Sieve tube elements
Companion cells
What is the function of sieve tube elements
Living cells which form tube for transporting sugars.
They have holes which allow solutes to pass through
What is the function of companion cells
Carry out living functions for themselves and sieve tube elements.
For example provide energy for active transport of solutes
What is meant by the term source?
Where assimilâtes are loaded into to the phloem
What is meant by the term sink
Where assimilates unload
Exam Question
When a bark is removed from a tree, the phloem was removed. If a complete ring of bark is removed, the tree trunk will swell above the cut
Suggests two reason why
Sugar cannot pass where it’s been cut
So…
This decreases water potential and the water moves into the cells.
Another answer could be
The damage causes cell division, so it can produce cells to store sugar
What is a dicotyledonous plant
A plant that has seeds made out of two parts
What two ways can water move through the plant
Symplast
Apoplast
Describe the apoplast pathway
At first the water goes through this pathway
- water is absorbed into cell wall
- travels through cortex (non living parts)
- via mass flow from high hydrostatic pressure to a low hydrostatic pressure
Describe the symplast pathway
Through living parts of the cell
- Water moves in through osmosis into the roots
- Moves through the cytoplasm and plasdostomata
Why do plants have a casparian strip
Forces water to move through plasma membrane
So what goes in is selected and others will be filtered out
How does the water get loaded into the xylem
1- endodermis moves mineral ions into xylem first through active transport
2- this decreases wp in xylem
3- so water will move into xylem through osmosis down wp gradient
4- generates root pressure which pushes water up xylem
Define transpiration
Loss of water vapour by evaporation through the stomata
What are the benefits and the opposite of benefit of transpiration
- Cools plant down
- Causes a transpiration stream (movement of water and minerals ions up the stem)
Downside
1. May cause loss of water, which means less turgor pressure, so plant will wilt
What factors affect transpiration
Temp
Humidity
Wind speed
Light intensity
How does temperature affect transpiration
The water molecules have more KE so they vibrate more,
Makes it easier for water to evaporate from leaf
Wp inside the leaf increases making water diffuse of leaf
How does humidity affect transpiration
As humidity increases the rate of transpiration decreases
More humid the more water vapour there in the air (the air is moister)
Decreases wp gradient between leaf and air
How does wind affect transpiration rate
Increases rate of transpiration
Water molecules will be blown away from the stomata Increases water potential gradient
So faster rate of transpiration
How does light intensity affect the rate of transpiration
More stomata will open
So greater photosynthesis
More CO2 means more gas exchange happens
So rate of transpiration increases
What does a potomètre measure
Measures water uptake by plant by estimating transpiration rate
How is water used up in plants
Turgor pressure
Photosynthesis
That’s why a potomètre is gives an estimation
…………..
………….
Define translocation
Movement of assimilâtes from source to sink
Why do plants use sucrose instead of glucose
Glucose can react
Can change wp of cells
Sucrose is big
How does phloem loading work
- H+ pumped out of companion cell through H+ pumps by active transport
- Which increases H+ concentration is in outside cell
- H+ wants to diffuse back into companion cell, so it’s gets co transported into Compnaian cell with sucrose
- Sucrose diffuses from companion cell into sieve tube element
- Which decreases wp inside sieve tube element
- Water moves into sieve tube element by osmosis which generates turgor pressure for mass flow
How does mass flow work
- Water has a high turgor pressure at source
- This flows down from source to sink down the pressure gradient
How does phloem unloading work
- Sucrose diffuses from phloem into sink
- Sucrose moves into cells which maintains concentration gradient between cells and phloem
- Loss of assimilates increases wp in the sieve tube element
H20 moves into cells via osmosis or enters xylem
What is a xérophytes
Plants like cacti which are adapted to live in dry environments
So their adaptions prevent them from losing water
Examples of xerophytes
Cacti
Thick waxy cuticle: reduces water loss by evaporation
Spines instead of leaves: reduces SA for water loss
Close their stomata: during the hottest time of the day when transpiration rates are high
Green stem: stem has lost of chlorophyll as cacti don’t have leaves
Shallow widespread roots: take advantage of an water
Fleshy stem: store water as they are ribbed so stem expands when there’s water
Examples of xerophytes
Marram grass
Sunken stomata in pits: sheltered from wind. Also can trap air in pits with help slow transpiration down
Hairs on epidermis: traps air around stomata which reduces wp between leaf and air
Roll up their leaves: in hot or windy conditions to trap air and to reduce SA
Thick wavy cuticle: to prevent water loss from epidermis
Dense spongy mesophyll: leaves fewer air spaces so less SA for diffusion
Tap root: grow vertically specialised for food storage
What is a hydrophyte
A plant that grows in water that need adaptions to cope with oxygen levels
Hydrophytes adaptions
Lillies,
Large flat leaves: contain air spaces which make them float, helps increase SA so they can absorb more sunlight
Open stomata on upper epidermis: exposed for efficient gas exchange as it’s hard to get air in water
Large air spaces: help plant float, act as store for oxygen, float on surface to obtain more light for photosynthesis
Small roots: Roots needed for anchorage not to absorb minerals
Thin or no wavy cuticle: don’t need them, they’re already in water
