How does higher temperature affect transpiration rate, assuming other conditions remain comparable?
It generally increases the rate by increasing evaporation and diffusion.
AQA GCSE Combined Science: Trilogy (8464) — Biology — Higher · 4.2.3.2
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How does higher temperature affect transpiration rate, assuming other conditions remain comparable?
It generally increases the rate by increasing evaporation and diffusion.
How does higher humidity affect transpiration rate, assuming other conditions remain comparable?
It decreases the rate by reducing the water-vapour concentration difference between the leaf and the air, reducing diffusion.
How does greater air movement affect transpiration rate, assuming other conditions remain comparable?
It increases the rate by removing water vapour from around the leaf, maintaining a steeper concentration gradient.
How does higher light intensity affect transpiration rate, assuming other conditions remain comparable?
It generally increases the rate because stomata open for gas exchange, allowing more water vapour to escape.
How do air spaces between mesophyll cells provide an opportunity for water to evaporate?
They expose a large internal surface area from which water can evaporate.
How does water vapour reach the stomata from within a leaf?
It moves through the interconnected air spaces between mesophyll cells.
How do the number and size of open stomata affect water vapour loss from a leaf, when other conditions are similar?
More or larger open stomata allow a greater rate of water vapour loss.
How is the average transpiration rate calculated over a selected time interval?
How is a compound unit for transpiration rate formed?
Combine a water-loss unit with a time unit, for example or .
How can the average transpiration rate over an interval be found from a graph of cumulative water loss against time?
Calculate the gradient over that interval.
How do root hair cell extensions increase uptake from the soil?
Their long, thin extensions provide a large surface area in contact with the soil.
How does water enter a root hair cell from the soil?
By osmosis, from the more dilute soil solution through the cell’s partially permeable membrane.
How can root hair cells take up mineral ions against their concentration gradient?
By active transport, using energy released by respiration.
Why do root hair cells contain many mitochondria?
To support the energy demand of active transport.
What is translocation in plants?
The movement of food molecules through the phloem.
Where does phloem transport dissolved sugars from and to?
From leaves to other parts of the plant.
What can happen to sugars transported to other parts of a plant?
They can be used immediately or stored.
How are the cells in phloem tubes arranged?
Elongated living cells are arranged end to end.
What do pores in the end walls of phloem cells allow?
Cell sap containing dissolved sugars can move from one cell to the next.
What is the purpose of representing numerical data as a graph?
To examine values and relationships visually.
Which graph types are appropriate for a continuous variable and for categories?
A line graph for a continuous variable; a bar chart for categories.
Where should the independent and dependent variables be placed on a graph?
Independent variable on the horizontal axis; dependent variable on the vertical axis.
What should each graph axis be labelled with?
The quantity and its units.
What makes a suitable scale for a graph axis?
Equal intervals that cover the data range and make effective use of the available space.
How should data be represented after choosing and labelling graph axes?
Plot values accurately and draw an appropriate line or bars.
What should you check before identifying a value in a graph, chart or table?
The title, headings, axis labels, units and scales, where applicable.
How do you read a numerical value from a graph or chart?
Locate its position and read the corresponding scale.
How do you identify a value in a table?
Find the appropriate row and column.
How should you describe patterns, trends or differences in displayed data?
Compare values using the quantities and units shown.
What must support an interpretation of a graph, chart or table?
The displayed data.