Time for a quick history lesson :
In the mid-17th Century, biologist Jan Baptist van Helmat suspected that plant growth had to come from water, after test he conducted showed no change in soil amount. However, carbon rich organic molecules can be found in plants. Water does not provide carbon. Thus, from that point, scientists discovered that water was an important element for photosynthesis, but not the sole component. The process of making food was thus defined as photosynthesis. This was a step for man kind to finding out what was.....
PHOTOSYNTHESIS
It is a process which occurs only during the day. Carbon dioxide is taken in by the stomata, water by the roots and light trapped by chlorophyll to produce glucose and oxygen.
Chloroplast
- disc like structures found in the cytoplasm of a plant cell
- chlorophyll found stacked up in chloroplast
- leaves are green due to chloroplast which reflects green light.
Glucose
- food for the plant
- stored as starch in other parts such as in the root, potato
Stomata
- found mostly on the underside of a leaf to prevent water loss
- has two guard cells at the sides responsible of opening and closing of stomata
- allow gas exchange
Here are some of the test you can do to find out if the leaf is making food(photosynthesising)
- Carbon dioxide bubbled through Calcium Hydroxide(lime water though now in sec 1 cannot be used), a white precipitate ( milky ) will be formed in the Calcium Hydroxide.
- Oxygen will relight a glowing splint
- Brighter glow is also counted as a presence of oxygen
- A variegated leaf is destarched(no light, kept in a dark room ) for 4 days, before boiled and soaked in ethanol to stop all chemical reaction within the leaf and decolourise it.
- Next, Iodine solution is dropped onto the leaf.
- If the leaf turns brown, Starch is absent.
- If it turns blue- black, Starch is present
