A container is filled with water from a lake and placed on an outside table in the sunlight. Healthy plant seedlings are placed in the container and left for 3 months. Distilled water is added to the container as required. At the end of each month a typical mature leaf grown during the previous 30 days is removed and drawn to the same scale. The diagram shows the three drawings that are made. Why is the leaf from month 3 the smallest?

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