At this point, the unit has covered human respiration, air and its components. We have also gone over the basic gas exchange that happens when we breathe. We are now ready to turn to plants. My third grade students would invariably have studied plants in some way perhaps in preschool and/or in previous grades. As we turn the unit in the direction of plants, I would probably begin with a review of the basic parts of a plant and their functions. One way I might do this depending on my timeframe is to take my class to the library media center to research plant parts. In that case, I might give them a copy of a plant drawing and a list of the parts and have them look them up, label the picture, and write the function of the parts. You could also do this with tree parts and then compare and contrast parts of trees and parts of plants. I have not included in my list the parts of a flower but that can also be included depending on what the objectives are. As the unit moves on and we begin to talk about how plants breathe, the children might research the parts of a leaf. As a learning technique, this type of activity will usually result in the children retaining the subject matter longer and with better understanding than if they are given the diagrams already labeled.
What are the basic parts of a plant?
Roots: One of the basic functions of roots is to help anchor the plant into the ground. It is also through the roots that the plant absorbs water from the soil. The roots are also a storage place for food that the plant needs to store for those times when it cannot produce its own food.
Stems: These parts function like arteries carrying water from the roots throughout the plant. Minerals in the water are deposited in the leaves. When water reaches the leaves some of it evaporates into the air.
Leaves: Inside leaf cells are green-pigmented chemicals, chlorophyll. Chlorophyll enables a plant to combine carbon dioxide into a simple sugar. The energy to do this comes from sunlight that is absorbed by the chlorophyll. The process called photosynthesis literally means, “to put together with light.”
From the sugar the plants make starch that they store throughout the plant. With compounds from the soil and soil bacteria, plants can manufacture vitamins and proteins.8
The size of plants leaves is a good indicator of how quickly water will evaporate from it. Broad leaf plants like maple will evaporate water quicker than other smaller leafed plants. Desert plants usually have thick, round leaves which reduce the surface and thereby the evaporation rate. They also have a waxy covering, which inhibits evaporation (see Appendix A, Experiment #5). 9