Section 3- Plant Nutrition and Transport P2 Flashcards
How is water absorbed by a plant?
Specialised root hair cells
-water is taken in by osmosis, there is usually a higher concentration of water in the soil than there is inside a plant so water is drawn into the cell by osmosis
How is a root hair cell adapted?
- plant roots grown long ‘hairs’ which stick out into the soil
- each branch will be covered by millions of these microscopic hairs
- this gives the plant a big surface area for absorbing water from the soil
Define Transpiration:
Transpiration is the loss of water from a plant
What is transpiration caused by?
Transpiration is caused by the evaporation and diffusion of water from a plant’s surface.
-most transpiration happens from the leaves
Define transpiration stream:
Transpiration stream is the constant flow of water through a plant from the roots to the leaves
How is a transpiration stream caused?
- the evaporation in the leaves creates a slight shortage of water in the leaf
- so more water is drawn up from the rest of the plant to replace it
- this cycle continues forming a transpiration stream
How has transpiration happened as a side effect from the way which leaves are adapted for photosynthesis?
-leaves have stomata for easy gas exchange, because there is more water inside the plant than in the air outside the water escapes from the leaves of the stomata by diffusion
What are the four main things which effect the rate of transpiration?
Light intensity
Temperature
Wind speed
Humidity
How does light intensity affect the rate of transpiration?
The brighter the light the greater the transpiration rate
- stomata close when it gets darker, photosynthesis cant happen in the dark, so they don’t need to be open to let carbon dioxide in
- when the stomata are closed very little water can escape
How does temperature affect the rate of transpiration?
The warmer it is the faster transpiration happens
-when its warm water particles have more energy to evaporate and diffuse out of the stomata
How does wind speed affect the rate of transpiration?
The higher the wind speed, the faster transpiration rate
- low wind speed, water vapour just surrounds the leaf, so thereis a high concentration inside and outside the leaf so diffusion doesn’t happen quickly
- high wind speed, water vapour is swept away, low water concentration outside of the leaf so diffusion happens quickly
How does humidity affect the rate of transpiration?
The drier the air around, the faster the transpiration rate
-if the air is humid, there’s a lot of water in it so there’s not much difference between the inside and the outside of the leaf, so diffusion rate is slow
