AQA GCSE Plant Organ System (Biology)
Plant organ system
An organ system contains organs working together to carry out a function for an organism.
The organ system of a plant, is the whole body of the plant.
The roots, stem and leaves are all organs.
All three of these organs will work together to form a plant organ system for transport of substances around the plant.
Structure of the Root.
Below is an image of the cross section of a root.
Water from the soil will enter the root, through the root hair cell.
After the water has entered the root hair cell it will travel across the cortex and then enter the xylem.
Root hair cell
Root hair cells absorb water and mineral ions from the soil.
They are adapted for this function:
1.Have a long, thin extension (root hair) that increases the cell’s surface area for absorption of water by osmosis and mineral ions by active transport.
2.Thin cell wall to make it easier for water and mineral ions to move through.
3.Large permanent vacuole to maintain a steep concentration gradient for osmosis.
4.Lots of mitochondria to release energy (ATP) for active transport of mineral ions.
Active transport of mineral ions into root hair cells.
Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient), using energy from respiration.
Mineral ions such as nitrate ions in the soil are actively transported from the soil (dilute solution) around the root hair cell, into the root hair cell (concentrated solution).
Absorption of water by osmosis into the root hair cell.
Osmosis is the diffusion of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane.
Now that mineral ions have been actively transported into the root hair cell.
Root hair cell will be a concentrated solution (many mineral ions, few water molecules.)
Soil solution will be dilute solution( few mineral ions, many water molecules).
As a result water will now move from the soil into the root hair cell by osmosis as shown below.
Water travelling across root cortex
Once water has entered the root hair cell, it will move cell to cell, across the cortex to the xylem.
The water will move cell to cell by osmosis from a dilute solution, to a more concentrated solution.
Practice Questions
1.Using the image below of a cross section of a root, label the position of the xylem and phloem.
2. State 3 ways that a root hair cell is adapted for its function.
3. State the name of the process that root hair cells use to absorb mineral ions such as nitrate ions.