Plant transport Flashcards
Where do plants absorb water from?
From the roots
What is the transport system made up?
A tissue called xylem and phloem
What does phloem transport?
Phloem transports sucrose and amino acids from the leaves where they are made to other parts of the plant
Describe the features of the xylem.
It is made of hollow dead cells joined end to end
the end walls have disappeared so a long open tube is formed
Where do xylem vessels run from?
From the roots, up through the stem and branch out into every leaf
What do xylem not contain?
Cytoplasm and nucleus
What are the xylem walls made up of ?
Made of cellulose and lignin.
What is lignin?
Lignin is very strong so xylem vessels help to keep plants upright
What is wood made up of?
Lignified xylem vessels
Describe the features of the phloem.
They are made of many cells joined end to end. They have sieve plates which have small holes in them- sieve tube elements
What direction do minerals travel in a xylem?
One way
What direction do organic molecules travel in the phloem?
Two way
What is a root cap?
At the very tip of the root hair cells. It is a layer of cells that protects the root as it grows through the soil.
What adaptation do root hair cells have?
They have a large surface area to increase the the rate of absorption
How do they absorb water?
By osmosis
How do they absorb ions?
By active transport
What is the function of the root hairs?
To absorb water and minerals from the soil. Water moves into a root by osmosis.
Describe how water is absorbed by the root hair cell.
The water in the soil is normally a more dilute solution so water diffuses into the root hair, down the concentration gradient and through the partially permeable surface membrane.
How does water travel up the xylem?
The pressure at the top of the vessels is lowered, while the pressure at eh bottom stays high.
How is the pressure at the top of the xylem vessels reduced?
It happens because of transpiration
What is transpiration?
Loss of water vapor from plant leaves by evaporation of water at the mesophyll cells followed by diffusion of water vapor through the stomata.
What is the transpiration stream?
The flow of water through a plant, from the roots to the leaves via the xylem vessels.
Describe the attractive forces in the xylem vessels
The attractive forces between the water molecule result in cohesion. These forces are greater than the forces trying to separate them, so the transpiration stream is pulling thin columns of water molecules, which resist the tendency to break apart.
What increases the rate of evaporation?
The many air spaces inside the leaf means that there is a large surface area of wet cells.
What do stomata do?
They allow water vapor to diffuse easily out of the leaf
What do the stomata reduce?
Reduces water potential inside the leaf which encourages more water to evaporate from the surfaces of the mesophyll cells
What is the rate of transpiration?
The rate at which a plant takes up water depends on the rate of transpiration- the faster a plant transpires the faster it takes up water
What is a potometre?
Records how fast the air/ water meniscus moves along the capillary tube- you can compare how fast the plant takes up water.
Describe the effect of temperature on transpiration.
On a hot day water will evaporate quickly from the leaves of a plant. Transpiration increases as the temperature increases
Describe the effect of humidity on transpiration.
Humidity means the moisture content of the air. The higher the humidity, the less water will evaporate from the leaves. This is because there is not much of a diffusion gradient for the water between the air spaces inside the leaf, and the wet air outside it. Transpiration decreases as humidity increases
Describe the effect of wind speed on transpiration.
On a windy day water evaporates more quickly than on a still day. Transpiration increases as wind speed increases
Describe the effect of Light intensity on transpiration.
In bright sunlight, a plant may open to supply plenty of CO2 for photosynthesis. More water therefore will evaporate from the leaves.
What is the direction of water movement in a plant?
Root hair- cortex- xylem- leaf - stomata
What happens if the plant is in short supply of water?
The plant will close its stomata, decreasing the rate of transpiration.
What happens if the leaves too much water loss?
The plant wilts because cells lose water by osmosis and become flaccid
What is translocation?
The movement of sucrose and amino acids in phloem from regions of production to regions of storage or to region of utilization in respiration or growth.
What can carbohydrates be made into?
Amino acids, proteins
What is a source?
The part of the a plant from which sucrose and amino acids are being trans located- leaves
What is the sink?
The part of the plant to which they are being trans located such as roots and flowers
What do the flowers use sucrose for?
To make fructose for when fruits are developing
What would act as a sink when it is a bud?
The leaves.
