Transport in Plants Flashcards
All 18 cards in this deck
What is transpiration?
The loss of water vapour from a plant by evaporation from the leaves, which then diffuses out through the stomata.
What are the steps in the transpiration stream, from soil to the air outside a leaf?
e.g. water moving through a leafy plant on a warm day- Water is absorbed into root hair cells by osmosis.
- It moves up the xylem as a continuous column (the transpiration stream).
- It evaporates from the leaf cells and diffuses out of the stomata.
What is the function of the guard cells around a stoma?
They open and close the stoma, controlling water loss by transpiration and the exchange of gases.
True or false? Water is pushed up the xylem by the roots using energy from respiration.
False. Evaporation of water from the leaves pulls the column of water up the xylem; no energy from the plant is needed.
How are nitrate ions taken up from the soil into root hair cells?
By active transport, against the concentration gradient, using energy from respiration.
What effect does increasing light intensity have on the rate of transpiration?
It increases it, because the stomata open wider in the light so more water vapour is lost.
What effect does air movement (wind) have on the rate of transpiration?
It increases it, because water vapour is blown away from the leaf, keeping a steep concentration gradient.
What effect does increasing temperature have on the rate of transpiration?
It increases it, because water evaporates and diffuses out of the leaf faster.
True or false? A plant in very humid air loses water faster than the same plant in dry air.
False. High humidity reduces the concentration gradient of water vapour, so transpiration is slower.
What are the steps to measure the rate of water uptake using a potometer?
e.g. testing the effect of air movement using a fan- Cut a leafy shoot and seal it into the potometer under water so no air leaks in.
- Measure how far the air bubble moves along the capillary tube in a set time.
- Repeat with the fan on, keeping temperature, light intensity and humidity the same.
What are the steps to calculate the rate of water uptake from potometer readings?
e.g. the air bubble moves 36 mm in 12 minutes- Find the distance moved: 36 mm.
- Find the time taken: 12 min.
- Rate = distance time = 3 mm/min.
What is translocation?
The movement of sucrose (and amino acids), dissolved in water, through the phloem from sources to sinks.
In translocation, what is meant by a source?
A part of the plant that makes or releases sucrose, e.g. the leaves.
In translocation, what is meant by a sink?
A part of the plant that uses or stores the sucrose, e.g. roots, growing shoots, flowers or fruits.
Does translocation require energy?
Yes — it is an active process using energy from respiration (active transport).
Which tissue transports water and mineral ions, and which transports sucrose?
Xylem transports water and mineral ions; phloem transports sucrose.
True or false? Translocation only moves sucrose upwards from the leaves.
False. Sucrose is moved in both directions in the phloem, to wherever the sinks are (e.g. down to the roots).
True or false? Most of the water vapour lost from a leaf escapes through the stomata.
True. Guard cells open and close the stomata, so they control how much water vapour is lost.