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Photosynthesis and Transpiration Can we demonstrate that transpiration is occuring? Materials: One or more potted plants (sweet potato vines, ivy, philodendron, and geraniums work well), small plastic bags, tape or wire ties. This experiment also works very well with leafy green plants growing outdoors—deciduous or evergreen—on dry, sunny days at any time of year. Instructions: Place small plastic bags over several leaves or groups of leaves. On outdoor plants, especially junipers and conifers, cover ends of small branches. Seal bags shut around stems with tape or wire ties. Make sure plant gets all the water and sun it needs during the next few days. What happens inside the bags? Why? ALTERNATE VERSION: Materials: Two wide mouthed jars or glasses, two clear plastic cups, two healthy geranium, philodendron, or sweet potato leaves with stems, two pieces of cardboard large enough to cover tops of jars, two small rocks or other heavy objects, food coloring, petroleum jelly, one or two cotton balls. Instructions: Fill both jars with water. Color the water in one jar with red food coloring. Punch a small hole in the middle of each piece of cardboard, just large enough to insert the stem of one leaf. Insert stems of leaves through holes and seal around hole with a small amount of petroleum jelly (to prevent evaporation through hole). Place cardboard over top of jars so that stems hang in water. Place plastic cups over leaves (leaves should be completely contained inside cups). Put a small weight on top of each cup. Place jars on a sunny windowsill. What happens inside the plastic cups? What happens to the food coloring? Use cotton balls to wipe moisture from glass on jar with colored water—is transpired water pink? SUGGESTION: If no moisture appears on the sides of plastic cups, trim leaf stems, cutting them on the diagonal, and try again. This will work. |
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