One day, a farmer noticed that one of his trees was starting to die. It had been a long and cold winter with short days, and the pond was frozen!

The farmer called Bob, a scientist, to come over. Bob told the farmer his tree was having a hard time doing "photosynthesis".

Photosynthesis is how plants make the food they need. They use the light from the sun to make glucose, or sugar.

Photosynthesis is when a plant uses Carbon Dioxide and water along with sunlight to make glucose (or sugar) for food and Oxygen for Humans and animals to breathe.

Photosynthesis needs three things, water, carbon dioxide, and sunlight. If a plant does not have enough sunlight from short days, or does not have enough water from a frozen pond, it may not be able to make food as well.