B4e-Transport in plants Flashcards
What is the structure of a xylem vessel?
Thick strengthened cellulose cell wall with a hollow lumen (dead cells)
What is the structure of a phloem?
Columns of living cells
What is the function of xylem?
They carry water and minerals from the roots up the shoot to the leaves in the transpiration system
What is the function of phloem?
They transport food substances mainly sugars up and down the stem to growing and storage tissues. (Translocation)
What is translocation?
The movement of food substances around the plant
How does water travel through a plant?
- root hairs absorb it from the soil
- then its transported through the plant up the stem to the leaves
- finally it evaporates from the leaves through transpiration
What is transpiration?
The evaporation and diffusion of water from inside leaves
How is transpiration and water loss from leaves a consequence of the way in which leaves are adapted for efficient photosynthesis?
Leaves have stomata in them so that gases can be easily exchanged. Due to the higher concentration of water inside the plant than the air outside, water escapes through the stomata
What effect does an increase in light intensity have on the transpiration rate?
The brighter the light, the greater the transpiration.
This is because stomata close when its dark because photosynthesis cant happen so theres no need for them to be open to let in Co2. This means water cant escape
What effect does an increase in temperature have on the transpiration rate?
The warmer it is, the faster transpiration happens.
This is because water particles have more energy to evaporate and diffuse out of the stomata
How does an increase in air movement affect the rate of transpiration?
Lots of air movement means transpiration happens faster.
This is because water vapour is swept away maintaining a low concentration of water in the air outside the leaf making diffusion happen quickly
How does a decrease in air humidity affect the rate of transpiration?
Dry air means faster transpiration.
This is because humid air has lots of water in it so the difference in concentration is not much meaning diffusion happens slower
How do root hairs help roots take up water by osmosis?
Microscopic hairs on the roots give the plant a big surface area for absorbing water
What does transpiration provide plants with water for?
Cooling
Photosynthesis
Support
Movement of minerals
How does a waxy cuticle reduce water loss?
It covers the upper epidermis making the upper surface of the leaf waterproof
