Transport in Plants Flashcards
All 15 cards in this deck
What is transpiration?
The evaporation of water from the leaves and its diffusion out through the stomata, which pulls water up the plant.
What are the steps of the transpiration stream?
e.g. water going from soil to air
- Water enters root hair cells by osmosis.
- Water is pulled up the xylem from roots to leaves.
- Water evaporates in the leaf and diffuses out through the stomata.
What are stomata and what do guard cells do?
Stomata are pores in the leaf surface; guard cells open and close them by changing shape as water enters or leaves.
Why are most stomata found on the lower surface of a leaf?
The lower surface is cooler and shaded, so less water is lost by evaporation.
Glucose made in photosynthesis is converted to which sugar for transport around the plant?
Sucrose.
What is translocation?
The movement of dissolved sucrose through the phloem from the leaves to other parts of the plant.
In which directions does sucrose move in the phloem?
From the leaves (source) down to the roots and up to buds and flowers (sinks).
True or false? Translocation of sucrose in the phloem needs energy.
True. Phloem is made of living cells, which use energy from respiration to transport sucrose around the plant.
How does increasing light intensity affect the rate of transpiration?
It increases it, because the stomata open wider in the light so more water vapour escapes.
How does air movement (wind) affect the rate of transpiration?
It increases it, because moving air removes water vapour from around the leaf.
How does increasing temperature affect the rate of water uptake by a plant?
It increases it, because water evaporates from the leaves faster.
In a fan investigation, why is water uptake also measured with the fan switched off?
To act as a control / baseline measurement to compare the effect of air movement.
What makes it possible for mineral ions to be carried from the roots up to the leaves?
They are dissolved in the water, so they travel up the xylem in the transpiration stream.
In the light, which gases diffuse into and out of a leaf through its open stomata?
Carbon dioxide diffuses in for photosynthesis; oxygen and water vapour diffuse out.
What is the equation for estimating the rate of water uptake with a potometer?
Rate = distance the air bubble moves ÷ time taken, e.g. in mm/min.