Plant organ system Flashcards – AQA GCSE Combined Science: Trilogy (8464) — Biology — Foundation

What route does water take through a plant, from entry at the root to the cells it reaches in the leaf?

Root hair cells → root cortex cells → xylem in the root and stem → leaf mesophyll cells.

What do root hair cells absorb from the soil?

Water and mineral ions.

How does the hair-like extension adapt a root hair cell for uptake?

It provides a large surface area.

How does a thin wall help a root hair cell absorb substances?

It provides a short pathway into the cell.

How does water enter a root hair cell from the soil?

By osmosis, from soil water at higher water potential into cell sap at lower water potential.

How can root hair cells absorb mineral ions against their concentration gradient?

By active transport, using energy released by respiration.

What role do mitochondria play in root hair cells?

They support the energy supply for active transport.

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 is the average transpiration rate calculated over a selected time interval?

$\text{Average rate} = \frac{\text{water lost during the interval}}{\text{duration of the interval}}$

How is a compound unit for transpiration rate formed?

Combine a water-loss unit with a time unit, for example $\mathrm{g/min}$ or $\mathrm{cm^3/h}$.

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.

What does a graph represent?

Numerical data as a visual representation on scaled axes.

What must you decide about the variables before plotting a graph?

Which variable to place on each axis.

What should each graph axis label include?

The quantity and its unit.

What makes a suitable scale for a graph axis?

It is consistent, includes the data and uses the available space effectively.

How should pairs of numerical values be plotted on a graph?

Plot each pair accurately against the axes.

How should you choose the line, curve or other form for a graph?

Choose a form suitable for the data.