Chapter 3 - Transport and immunity Flashcards
What is the function of xylem and what does it transport (what direction)
- Xylem transports water and mineral salts from roots to plant stem
- It also helps support the plant
What is the function of phloem and what does it transport (what direction)
- Phloem transports substances that the plant has made e.g. glucose, from the leaves and storage organs to all other parts of the plant
Label this cross-section of a stem
Label this cross-section of a root
What is the path that water takes from the soil to the leaves
Water in soil –> Root hair cell –> Across root cortex cells –> into xylem vessels –> Up through xylem vessels in the stem –> Mesophyll cells in leaf
How does a root hair cell absorb water
By osmosis
How does a root hair cell abosrb mineral ions
By diffusion and active transport
What practical can be used to visibly see water uptake
- Stand a celary stalk in coloured water
- You will see the colour moving up, through the celary, through the stem and into the veins of the leaves
- If you cut the stem, you will see coloured dots which are xylem vessels through which coloured water is flowing upwards
What is the definition of transpiration
The loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata
How does transpiration occur in the leaf?
- Water moves out of the xylem vessels and into the palisade mesophyll and spongy mesophyll by osmosis
- Water seeps into the cell walls of the mesophyll cells
- Some of the water in these cell walls evaporate (from liquid water to water vapour)
- This produces a very high humidity in the air spaces in the leaf
- The water vapour diffuses out of the air spaces, through the stomata, into the air as water vapour
Why do mesophyll cells have a large surface area
- A lot of water can evaporate in a shorter period of time
- The interconnecting air spaces inside the leaf mean that the water vapour can easily diffuse through the leaf and out into the air through the stomata
Explain transpiration pull and cohesion
- Transpiration provides the pulling force that makes water flow up through xylem vessels
- When water vapour diffuses out through the stomata, it decreases the water potential inside the leaf.
- With less water in the leaf, the water pressure at the top is reduced, so that it is less pressure than at the bottom of the leaf.
- Water flows from the bottom of the xylem (high pressure) to the top of the xylem vessels (low pressure)
- THis force is called “Transpiration pull”
Why in transpiration does water flow up in an unbroken column
Because the water molecules are attracted to each other and held together by cohesion
How are leaves held out flat, to expose the maximum area to sunlight for photosynthesis
- (what features help them)
- Turgor pressure in mesophyll cells
- Xylem vessels in the veins of the leaf
How does wilting occur in a plant
- Wiltioccurs when transpiration is occuring faster than water being drawn up from the soil, the leaves dont have enough water and become floppy
How does wilting help a plant
- Helps a plant survive when it is short of water
- When the leaves collapse, a smaller surface area is exposed to the air, transpiration occurs slower, so the plant loses less water
What is the rate of transpiration affected by
- High tempurature speeds it up
- High humidity speeds it up
Why does high tempurature speeds up the rate of transpiration
- Water molecules have more kinetic energy at high tempuratures
- This speeds up the rate of evaporation on the surfaces of mesophyll cells, and speeds up the diffusion of water vapour through the leaf and out through the stomata
What is the definition of translocation
- The movement of sucrose and amino acids in phloem:
- From regions of production to regions of storage or where they are used in respiration and growth
What is a source and a sink
- A source is the part of the plant from which sucrose and amino acids are being transported to
- A sink is the part of the plant to which sucrose and amino acids are being transported to
What is special about the source and sink
They can be in different places at different times of year
In summer when sucrose is produced in leaves, where could the sucrose be transported to and for what reason
- The roots - changed into starch and is stored
- Flowers or fruits - changed into fructrose for nectar or to make the fruits sweet
- any part of the plant that requires energy - respiration
In winter when sucrose isn’t produced in leaves, where does energy come from
- The roots - where the starch is stored
- The starch is broken down to sucrose, is transported to leaves, converted to glucose, respiration occurs
In mammals what is the circulatory system made out of
- Blood vessels
- The heart
- Valves
What is the difference between double and single circulatory systems
- In single circulatory systems, blood passes through the heart once on a complete jounrey whereas it passes through the heart twice in double circulation systems
Why is double circulation better than single
- The blood goes back to the heart after being oxygenated
- More efficient at moving oxygen to the cells, because the oxygenated blood is given an extra “push” by the heart
What do valves do
Prevent backflow of blood
What does the right atrium do
Recieves deoxygenated blood
What is the septum’s function
Separates oxygenated and deoxygenated blood
what is the right ventricles function
pumps deoxygenated blood to the lungs
What is the vena cavas function
Carries deoxygenated blood from the body
What is the aorta’s function
carries oxygenated blood to the body
What does the pulmonary artery do
carries deoxygenated blood to the lungs