Biology π | Transport in plants | 8 Flashcards
Vascular bundles consist ofβ¦
Xylem vessels and phloem tubes.
What is the function of xylem?
Transporting water and minerals from the roots to the stem and leaf
What is the function of phloem?
Transporting sucrose and amino acids made by the plant.
In the cross-section of a root or stem, where is xylem tissue found?
In the center.
How is xylem and phloem arranged in the stem and how does this help the plant?
In a more spread out out way, which thanks to the lignin keeps it stable.
What is the cortex?
The cells lying between the epidermis and vascular tissue of a stem or root.
Where is the cambium?
It is a thin layer of cells between the xylem and phloem
What is the stele?
The central part of the root containing vascular tissue.
How do water molecules get pushed up the xylem vessels?
Water molecules attract each other. Pressure at the top of the vessels is removed from transpiration or photosynthesis and the pressure at the bottom stays high, forcing it upwards.
What are the characteristics of Phloem that differs from the xylem?
- A two-way flow
- Cells have end walls
- It is living
- It transports food
What are the characteristics of xylem that differentiate it from phloem?
- A thick cell wall with lignin
- No cytoplasm inside
- A one way flow
- Transports water.
Why do xylem vessels have thick walls with lignin?
It makes the vessels waterproof from leaks and keeps the plant strong.
Why do xylem vessels have no cell contents?
This maximises the water volume transported and leads to less resistance.
Why are cells joined end to end with no cross walls in xylem vessels?
This allows the continuous transport of water as cell walls are removed.
From where do plants take in water?
Root hairs.
What is the root cap?
A tough protective layer of cells over a root tip.
How does water go from the soil to the xylem vessels?
- It moves into the root hair through osmosis as the cytoplasm and cell sap inside is concentrated
- Water travels by osmosis to root cortex from cell to cell
- Reaches xylem vessels
What is the purpose of root hair cells?
It increases the surface area of the cell for osmosis to happen.
How does water at the bottom of xylem vessels reach the top?
The pressure at the bottom is high and as water transpires out and loses pressure at the top water flows up the vessels.
Define transpiration.
The loss of water vapour from leaves by evaporation of water at the surface of mesophyll cells followed by the diffusion of water through the stomata.
What 4 factors affect transpiration?
Temperature, light intensity, air flow, and humidity
What are the functions of transpiration?
- Transporting mineral ions
- Provides water for cell turgidity
- Provides water to leaves for photosynthesis
- Keeps leaves cool.
How does transpiration keep leaves cool?
Conversion of liquid water to water vapour requires heat energy.
How are root hair cells adapted for transpiration?
They provide a huge surface area that water can be absorbed through, increasing quantity of water that moves through the plant.
