Photosynthesis

The student will:

Learn what photosynthesis is and how it helps plants.

Learn what a plant needs for photosynthesis.

What is photosynthesis?

Plants make their own food. This process is called photosynthesis.

Where does photosynthesis occur? Photosynthesis occurs in the

leaves of a plant.

What is needed for photosynthesis to occur? Light is needed for photosynthesis to

occur. The plant’s leaves use the light to make a sugar called glucose.

Carbon dioxide enters the leaf through holes called stomata

Why do plants need glucose?

Glucose is the food for the plant. It gives the plant energy to grow.

How much glucose does a plant make? Plants make enough glucose to be used

during the night and on cloudy days when they don’t get sunlight. The extra glucose is stored in the plant’s leaves and other parts.

How does photosynthesis help us? During the process of photosynthesis,

oxygen is produced. We use this oxygen to breathe.

Why is photosynthesis important to us? We cannot make our own food (glucose,

energy), we must get our food from plants. Plants are the first step in the food chain. Animals get the energy stored in plants when

they eat them.

Respiration When plants use the glucose and oxygen

made during photosynthesis to make energy, carbon dioxide, and water for the plant, it is

called respiration. Photosynthesis stores the energy and

respiration releases that energy to leaves through xylem tissue.

What is the chemical equation for cellular respiration?

Transpiration Transpiration occurs when water is

evaporated from the leaves through the stomata.

Xylem draws more water up through the roots to replace the evaporated water

And the cycle continues……………

Plants give off water from their surfaces in a process called

transpiration. This water leaves through stomata, which are tiny

openings on the surface of a plant and are especially abundant on the

undersides of leaves. Stomata open and close to let gases in and out.

Water vapor is one of the released gases.

Transpiration

Some leaves have more than a million stomata. In forests, trees need a large

amount of water because about 98 percent of the water they take in is lost

through the stomata.

The leaves of tropical and temperate plants have stomata that are open longer periods

of time and have larger openings than those of desert plants. In the desert, plants can

survive with less water because the stomata of the plants do not open as wide and

remain closed most of the time. The time stomata remain open as well as the size of their openings are largely controlled by the

availability of water and of sunlight.

As the water evaporates from leaves during transpiration, more water is pulled into the plant at the roots. The water moves from the roots to the leaves through tubelike structures called xylem tubes. The water carries nutrients through plants.

What do you think would happen if we put a plastic bag over a leaf on a tree and left it over night?