PARTS OF A FLOWER
During the Paleozoic Era (approximately 542 to 251 million years ago), the earth resembled a giant swamp and plants relied on water to disperse their seeds in order to reproduce. However, as the earth developed a drier and more seasonal climate, plants needed to find a new way of scattering their seeds. The outcome of this evolutionary change was plants that could disperse their seeds via the wind, insects, birds, and other animal species. These plants are gymnosperms (plants that bear naked seeds, mostly species in the coniferous tree family) and angiosperms (flowering plants, such as an apple tree). About 75 percent of plants on Earth today and almost all of the vegetables and fruits we see in our gardens are angiosperms.
There are many different ways that plants can be pollinated—and often just the way a plant looks can provide us with useful tips. For example, plants relying on wind for pollination are often structured with exposed, easily moved seeds, in order to maximize accessibility by the wind. Think of wind-pollinated grasses that often have anthers extending from long filaments—literally seeds hanging in the breeze! The stigma (the top part of the pistil) of a wind-pollinated plant is often feathery looking and is not protected by petals in order to best facilitate an easy landing strip for the airborne pollen. Plants that use insects and birds as pollinators, on the other hand, often have brightly colored fragrant flowers and sweet tasting nectar to attract pollinators. Once a pollinator lands on the petals, the pollen on the anthers will rub off on the insect’s body; when this insect then flies to the next flower, the pollen will rub off onto that flower’s stigma. Once on the stigma, the pollen travels down to the base of the pistil where the egg is located. After the egg is fertilized, the plant’s flower begins to fade, and the ovary of the plant will begin turning into fruit. This fruit will serve two important functions: to protect the seed and to be a lure for animals to eat, and thereby distribute, the plant’s seeds. (Source: Loewer 1995, Davis 2008)
WHAT IS A FRUIT?
A plant’s fruit can only be formed once the flower has been pollinated. The main purpose of the fruit is to shelter the seed. Fruits vary greatly in size and shape and can accommodate anywhere from one to one thousand seeds!
Though we all love eating juicy fruits, there are many other wonderful parts of the plants that we eat and enjoy! As harvest time approaches in your garden, it is important to make your students aware of all the different parts of plants that you can enjoy. A few examples include leaves (salad greens, spinach), roots (carrots, beets), stems (asparagus, celery), and fruit (squash, tomatoes). Encourage your students to be food explorers and cook with them in the classroom. If space and facilities allow it, think about storing, freezing, and canning your harvest to last you through the winter.