Water movemnet in plants

Inculding osmosis and cell wall structure.

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  • Created by: Jenna k
  • Created on: 29-03-14 14:51
What is osmosis?
Osmosis is the movement of water form a high water potential to a lower water potential through a partically permeable membrane.
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What is water potential?
Water potentail is the concentration of water molecules. If 0 then it is pure water. If below zero then there is a solute disolved in the water making it less pure.
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What is water potential measureed in?
Units of pressure. Pascals (Pa)
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Explain how movement of water into a raoot hair cell occures.
The water in the soil is almost pure water. The water in the root epidermas has a high solute level, thus lowering the water potential and moving the water across the partially permable plasma membrane into the Root hair cell.
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Why does the root epidermal cell have a lower water potential?
Because it has a high solute potentail. There are mineral ion, amino acids and sugars present in the cytoplasm of the epidermal cell.
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Define hypertonic
Hypertonic is when water potential outside the cell is lower and the water moves out of the cell by osmosis. Thus causing the cell to shrivel.
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Define hypotonic
This is when the water potentail is lower on the inside of the cell causing the water to move into the cell by osmosis and causing it to burst.
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Define isotonic
An isotonic solution is when the water potential is equall outside to the water potential inside the cell. Thus no movement occurs.
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Why are root epidermal cell suited to water transport?
epidermal cells have a thin permeable wall thus increasing the rate of diffusuion. Also they are exptensive so there is a large surface area for absorbtion of water and other minerals.
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Name three roots water can take to reach the vascular bundle.
Vascular, apoplastic and symplastic pathways
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Explain the vascular pathway.
This is when the water enters the cell wall of each cell it travels through. But it travels into the vacuol of each cell.
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Explain the apoplastic pathway.
The aoplastic pathway consists of water traveling around the cells in the intercellular space. This occurs because the cell wall is made up of cellulose which is impermiable to water.
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Explain the symplastic pathway
This is when the water enters the cell through the plasmademta and travels through the cytoplasm and out through the plasmadesmta on the other side. This is due to the higher water potential in the epidermal cells wich will move to lower wp next cell
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Which of the pathways will end at the endodermis?
The apoplastic pathway.
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Why does the apoplastic pathway stop at the endodermis?
In the endodermis there is a impermiable strip that stops the apoplastic path. (casparians strip) The water is therefore diverted to the symplastic or vacular pathways.
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Define dicotylendonous root.
This is a root of a flowering plant. Thus an unlternative name to a root.
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Explain water movement through a root cell.
Water passes into the root hair cells in the epidermis by osmosis. This then travels through prenchyma tissue called the cortext. The pathways are determined in the cortext. Then through the endodermis and into the vasular bundle.
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What is the vascular bundle?
It is a colletion is tissues that make up the xylm and phloem.
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Define Endodermis
Endodermis is a layer of tissue that houses the casparian strip after the cortext
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Define epidermis.
This is the extermal layer of tisseu where the root hairs are located.
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How does water move up the xylem?
The endodermal cell actively transport salts into the xylem, decreasing the water potential ans thus a water potential gradient if formed which creats root pressure which helps the water being sucked up the xylem to the leaves.
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What affects root pressure?
Metablobil inhibitors, Tempriture and reducation in the amount of oxygen.
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How do metabolic inhibitors affect root pressure?
They prevent resipration from occureing, Thus stoping ATP being formed and no active transport takes place.
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How does tempriture affect root pressure?
When tempriture increased root pressure increased due to the kenetic energy and the metabolic rate being affected by heat.
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How does reducing the amount of oxygen affect root pressure?
If there is less oxygen then there is less respiration happening and less ATP being formed so active transport doesnt occure as readily
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Define Mesophyll layer.
This is the single celled explance of cells that make up organs such as the leaves in a plant.
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Describe transiprtaion.
Transipration is the loss of water through diffusion out of the epidermis.
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Describe the movement through the mesophyll layer.
Water is lost by transpiration in the stomata in the epidermis of the mesophyll layer. This lowers the wp of The stomata cell thus causing water to move into it by osmosis and thus the process continues.
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What is transpiration pull?
This is when the loss of water through a stomata causes water to move it to the next cell by osmosis to then diffues into the outer atmospher. Thus creating a single movement of water through one cell. Like traffic.
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Describe Cohesion-tension.
Water forms hydorgen bonds between the water particle. Thus when one particle moves the next is dragged along with it and so on. Thus creating a continuous stream of water through the xylem and mesophyll layer.
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What is the role of transpiration?
To transport water around the plant.
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Why it important that water is transported around the plant?
It's not the water the plant needs, so much, its the minerals, sugars and amino acids dissolved in the water that the plant wants and needs.
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What are the factors that effect the rate of transporation?
Humidity, air movement, tempriture and light.
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Describe the effects of Tempriture on the rate of transporation.
Tempriture increases thus increaseing the kenetic energy of the water molecules, thus making then evaporate quicker and the rate of transporation is increased.
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Descirbe the effects of humidity on the rate of transpiration.
Humidity means that the water potentail outside the plant is higher, thus decreasing the differacnce in water potentail in and outside of the cells. So the water does not move as quickly and the rate is decreased.
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Descirbe the effects of Light on the rate of transpiration.
Light means that the stamata are open and CO2 is being diffused into the plant. If the stomata are open then water diffuses out more readily thus increaseing the rate of transpiration.
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Describe the effects of air movement on the rate of transpiration.
If there is little air movement (wind) Then a bubble forms around the stomata. This bubble will have a high water potential thus decreasing the amount of water that diffuses out of the stomata. If there is air movement then the bubble doesn't form...
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What monosaccharide makes up cellulose?
beta glucose
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What is the role of the cell wall?
To give mechanical support and strength to the cell. Thus nor alowing cells to burst or shrivel.
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What is the formation of cellulose
Cellulose is made up of many chains of bonded beta glucose molecules. They form long matirx of fribrels that become linked to parrellel chains by hydrogen bonds of the C02HO bonds.
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Define middle lamella.
Middle lamella are the intercellular spaces inbetween each cell wall. They mark the bounderies of the cell.
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What bonds the beta glucose into long fibrels?
Condesation reactions, which remove water form a glycosidic bond between each molecule.
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How do you brake the bonds of cellulose.
You would have to have very high tempritures to brake the hydorgen bonds of the fibrels to separate the chains then add a lot of water in, to hydorlise the gycosidic bonds of the glucsoe.
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Card 2


What is water potential?


Water potentail is the concentration of water molecules. If 0 then it is pure water. If below zero then there is a solute disolved in the water making it less pure.

Card 3


What is water potential measureed in?


Preview of the front of card 3

Card 4


Explain how movement of water into a raoot hair cell occures.


Preview of the front of card 4

Card 5


Why does the root epidermal cell have a lower water potential?


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