Plants get their energy from food – just like you and me. The big difference is that, unlike you and me, they can make their food from a couple of simple raw materials. Plants make glucose from water absorbed by their roots from the ground and carbon dioxide absorbed from the air by their leaves. The water is broken apart to release hydrogen and the oxygen goes back into the atmosphere. This hydrogen is combined with carbon dioxide to make the simple sugar – glucose. The process is made possible by the green pigment chlorophyll which absorbs blue and red wavelengths of light. The whole sequence, known as photosynthesis, can be described by the following word equation…
The somewhat dramatic arrow is meant to show that the process is a complex one, not a single step.
This process happens in the green parts of plants; stems and leaves. Cells called palisade cells line the surface of the leaf and are packed with chloroplasts. The chloroplasts are tiny organelles full of chlorophyll that actually do the tricky work of photosynthesis. Leaves have a spongy inner region that allows carbon dioxide gas to diffuse in and oxygen to diffuse out. I will write about leaf structure in more detail in part two.
In the meantime, other posts you should read are photosynthesis, plant nutrients part one, a typical plant cell and respiration.
Questions…
- Other than chloroplasts, suggest another feature of a plant cell that you would never find in an animal cell.
- Name a mineral that may be dissolved in the water absorbed by plants and how it is used by the plants.
- How do we know that chlorophyll does not use the green wavelengths of light for photosynthesis?
- A palisade cell has a specialised job. Suggest another specialised plant cell.
1 A large vacuole
2 Hydrogen as it is used to make glucose when it is mixed with carbon dioxide
3 As it absorbs blue and red wave lengths and these wave lengths make a green colour
4 A root cell
Thank you for another helpful post sir
Q1 – excellent
Q2 – the hydrogen used in photosynthesis comes from water being split into hydrogen and oxygen by sunlight and chlorophyll – there is very little free hydrogen around on Earth because it tends to react and become water. You can read about the minerals needed by plants here.
Q3 – not quite. It is absorbing the blue and red wavelengths and reflecting the green wavelength – a little reminder here
Q4 – yes – although more specifically a root hair cell so that it is not confused with a just a regular cell within the root