Embryonic Development

<h1>Text Preview</h1> <p>The zygote, or fertilized egg, eventually develops into a seed that gives rise to a new plant. The first step in this process is the formation of the plant embryo. The zygote undergoes mitosis to form a basal cell and a terminal cell. The terminal cell divides to form the embryo. The basal cell divides to form the suspensor. The suspensor pushes the embryo into the endosperm and transfers nutrients and hormones that the embryo will need to grow.</p> <p>As the embryo develops, seed leaves form. Embryos contain one or two seed leaves called cotyledons. Plants are classified as monocots when they have one seed leaf and as dicots when they have two. The ovule loses water and matures into a seed when a protective seed coat forms. While the ovule is maturing into a seed, the flower’s ovary develops into the rest of the fruit. </p> <p>Simple fruits form from a single ovary. They may be dry, such as in chestnuts and corn, or fleshy, as in oranges and apples. Aggregate fruits form from multiple ovaries of a single flower. Raspberries and blackberries are examples of aggregate fruits. Multiple fruits develop from the ovaries of different flowers that fuse together. Pineapples and figs are multiple fruits.</p> <p>Some other parts of a flower also contribute to what we call “fruit” in the grocery store. For example, the flesh of an apple we bite into results from the enlarged base or receptacle of the flower. The ovary develops into the apple core. The seeds are inside the core; their tough brown coat is the ovule wall. Opposite the apple stem, the sepals are visible at the base of the apple, sometimes with the stamens still attached.</p> <p>Why do plants go through all the trouble of producing fruit when all that’s needed to start a new plant is the seed?</p> <p>Birds, animals, and other creatures eat the plant’s fruit. This facilitates wide dispersal of the plant’s seeds. This is important since plants don’t move around. Seed dispersal ensures that the new plants don’t compete with the parent plant for sunlight, water, and minerals. </p> <p>When environmental conditions such as moisture, temperature, and sunlight are right, a seed will germinate, or grow. The root of the embryo emerges first. In monocots such as wheat, rice, and corn, the shoot, or leafy portion, of the embryo then breaks through the soil’s surface. The seed’s food reserves stay underground.</p> <p>In dicots such as beans, peas, potatoes, and sunflowers, the root forms a hook that pushes through the surface. Then in response to sunlight, the hook straightens and the shoot emerges. The food reserves are either brought above the surface of the soil, as in a bean, or remain below ground, as in a pea.</p> <p>Once a portion of the plant is above ground, it uses sunlight rather than its food reserves to meet its energy needs for development and growth. </p> <p id="TextCopyright">Copyright 2006 The Regents of the University of California and Monterey Institute for Technology and Education</p>