Chapter 8: Transport In Plant Flashcards
Function of xylem
transport of water and mineral ions, and support
Function of phloem
transport of sucrose and amino acids
Positions of phloem and xylem
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Xylem is always on the inside while phloem is on outside
Structure of xylem vessels
(a) thick walls with lignin (to withstand pressure changes as water moves through plant)
(b) no cell contents
(c) cells joined end to end with no cross walls to form a long continuous tube
Root hair cell function
Plants absorb water from the soil by osmosis
Function of root hair cells
Plants absorb water from the soil by osmosis
Why do root hair cells have a large surface area?
large surface area of root hairs increases the uptake of water and mineral ions
Pathway taken by water in plants
root hair cells, root cortex cells, xylem, mesophyll cells
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Describe transpiration
the loss of water vapour from leaves
Steps of transpiration in plants?
water evaporates from the surfaces of the mesophyll cells into the air spaces and then diffuses out of the leaves through the stomata as water vapour
What is water vapour relative of?
the large internal surface area provided by the interconnecting air spaces between mesophyll cells and the size and number of stomata
How does transpiration contribute to water movement in xylem?
transpiration pull draws up a column of water molecules, held together by forces of attraction between water molecules
Factors that affect the rate of transpiration
- Temperature: Higher temperatures increase transpiration as the air can hold more water vapor.
- Humidity: Lower humidity (drier air) increases transpiration as the air has a higher capacity to absorb water vapor.
- Wind speed: Increased wind speed enhances the removal of water vapor from the leaf surface, increasing transpiration.
- Light intensity: Higher light intensity can increase the stomatal opening, leading to increased transpiration.
Explain how and why wilting occurs
When the leaves lose a lot of water from transpiration, the leaves start to face down away from direct sunlight so the leaves don’t get too hot and therefore the leaves are able to absorb more water.
Translocation
the movement of sucrose and amino acids in phloem from sources to sinks