Vascular Bundles in sugar cane.
Below: detail of one bundle
Bioviewers Box 78
The stem of a flowering plant
The positions are different in stems compared to roots. In a stem they are round the outside.
Position of vascular tissues in the roots
In roots they are found in the centre.
For photosynthesis to happen all the “ingredients” need to be present.
If there are inadequate ingredients photosynthesis will stop or slow down.
The factor that is in shortest supply will be the one that limits the rate of photosynthesis and is called a “limiting factor”.
Shortage of CO2
Shortage of light
Lack of chlorophyll
A plant has plenty of water, carbon dioxide and chlorophyll, but it is night.
Hence, photosynthesis cannot take place due to lack of light.
Light is the limiting factor.
Often this sort of information is shown in a graph…
A Light intensity is limiting the rate of reaction
B CO2 is limiting the rate of reaction
C The difference between the lines is due to different temperatures.
Quick Quiz 2
2. Give 2 structural features of a leaf that make it a good design for photosynthesis.
3. Why do you think that the palisade cells are near the surface of the leaf?
4. Name the cells that surround the stomatal openings.
5. The spongy mesophyll cells are loosely arranged. Explain the significance of this.
6. Which 3 factors limit the rate of photosynthesis?
1. How is glucose carried from the leaves to every part of the plant?
Transported in phloem tubes (water in xylem)
Large surface area, thin, stomata, veins
To absorb as much sunlight as possible in chloroplasts
Large spaces between cells allow gases to diffuse quickly
Quantity of light, carbon dioxide, temperature