GROWTH RATE

PURPOSE : To measure the growth rate of a plant stem grown in the shade

MATERIALS : 2 Green onion

                          Glass

                          Soil

                          Ruler

                          Marking pen (black)

PROCEDURE :

•  Measure about 6 inches (15 cm) from the root of each onion and have an adult cut off the stem.

•  Fill the glass with soil.

• Moisten the soil with water.

•  Stick the closed end of the marking pen into the soil near the glass and move it back and forth to make a hole. The hole needs to be large enough to bury the onion root 2 inches (5 cm) below the soil surface.

•  Insert the onion, root down, into the hole.

•  Push the soil around the onion to secure it in place.

•  Do this for both the onions. Place the glass away from a window.

•  Use the marking pen to color around the end of each onion stem.

• Use the pen to mark the stem each day. The new growth will grow out of the outer skin covering.

• Observe and mark the stem daily for 2 weeks.

RESULTS : The stems may grow at different rates, but they can grow as much as 12 inches (30 cm) in 2 weeks .

WHY ? Plants need water, nutrients, and sun light to grow properly. Their growth changes when any one of these three factors is lacking. The lack of sufficient sunlight causes a plant to grow very tall. Many bedding plants have very long stems because they do not receive enough sunlight. Trees in a thick forest are often thin and very tall so that they can reach upward to the sun. Your onion plant has grown very tall because of the lack of sunlight.