Investigating the Effect of Light Intensity on Photosynthesis in a Pondweed

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Investigating the Effect of Light Intensity on Photosynthesis in a Pondweed

Aim:

To investigate how the rate of photosynthesis changes at different

light intensities, with a pondweed.

Prediction:

I predict that the oxygen bubbles will decrease when the lamp is

further away from the measuring cylinder, because light intensity is a

factor of photosynthesis. The plant may stop photosynthesising when

the pondweed is at the furthest distance from the lamp (8cm). Without

light, the plant will stop the photosynthesising process, because,

light is a limited factor. However once a particular light intensity

is reached the rate of photosynthesis stays constant, even if the

light intensity is the greatest. If I plot distance of the lamp,

against the number of bubbles per 2 minuets, I will get a straight

linear graph which will not go through the origin.

Introduction:

Photosynthesis is the process by which green plants use light to

synthesize organic compounds from carbon dioxide and water. In the

process oxygen and water are released. The glucose produced in the

photosynthesis reaction can be converted to sucrose and carried to

other parts of the plant in phloem vessels. Glucose can also be

converted into starch and stored (the starch can later be turned back

into glucose and used in respiration). Oxygen is a 'waste' product of

photosynthesis. Photosynthesis takes place in the mesophyll cells

inside a green plant's leaves.

6 CO2 + 6 H2O givesC6H12O6 + 6 O2

Carbon Dioxide + Water gives Glucose + Oxygen

A limiting factor is one that controls a process, such as organism

growth or species population size or distribution. In photosynthesis

the rate is affected by three factors, temperature, carbon dioxide

concentration and light. Not enough light can slow down the rate of

photosynthesis, without enough light a plant cannot photosynthesise

very fast, even if there is plenty of water and carbon dioxide.

Increasing the light intensity will make photosynthesis faster.

Variables:

In this experiment there are a few things we have to keep the same.

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