Extracting life from a plant
Plants are living creatures just like Dad (OK, so plants are a little smarter). Plants need food and water just like people. But how do plants get food? Plants get their nutrients via the water they take in. Nutrients from the soil get mixed up with the ground water. The plant takes in the ground water with the sneaky nutrients concealed inside. OK Reeko, so how do plants take in water, I’ve never seen them slurping it up with a straw? This experiment should shed some light on this question.
- Fill the bottle with water.
- Take a freshly cut leaf or flower, wrap clay around the stem and place the stem into the bottle. Make sure the clay fits snugly around the mouth of the bottle.
- Poke a hole in the clay and stick a straw through the hole. Make sure the clay fits tightly around the straw so that no air leaks will occur. Make sure the straw is not touching the water!
- Stand in front of a mirror so you can see the bottle. Suck the air out of the bottle (unless you’re ready to skip ahead to the CPR lesson, make sure the straw is not touching the water!). This experiment will not work if there are any air leaks.
Heh, heh – pretty odd, huh? There are holes in the leaf called stomata and tiny tubes called xylem which run down the stem. The leaf and stem act as a straw for the plant. The stomata act as the straws hole and the xylem act as the straw itself. As you drew air out of the plant, more air was drawn into the bottle through the stomata and xylem. This is the same system that water moves in a plant.
Carbon dioxide enters a leaf from the air. The epidermis (outer surface) of the leaf has many tiny pores. These openings, called stomata, enable carbon dioxide to enter the leaf. A leaf has many stomata. For example, a cottonwood leaf may have 1 million stomata, and a sunflower leaf nearly 2 million. However, the pores are so small that they make up less than 1 per cent of the leaf’s surface. In most plants that grow in full sun, the majority of the stomata are in the shaded lower epidermis of the leaves. In many other plants, the stomata are about equally divided between the upper and lower epidermis.
A leaf obtains water that has been absorbed by the plant’s roots. This water travels up the stem and enters the leaf through the petiole. Tiny tubes in the leaf’s veins carry the water throughout the blade. These tubes make up the vein’s xylem (water-transporting tissue).