We are all aware that a plant has different stages it goes through during it’s life cycle. These stages must start somewhere? We will begin with the seed and a plants process of germination.
Most plants reproduce by way of seed. A flower will be pollinated forming a seed. Then the plant will spread the seed and the life cycle begins again. The seed is very important as it is passing down information in it’s genes for the next generation of plants. To insure success of future generations the seed has specific attributes and functions. Seeds have three main parts: the embryo, food storage tissue and the seed covering.
The embryo consists of the epicotyl ( plant shoot ), hypocotyl ( stem between root and shoot ), radide/radical ( beginning of root system ), and cotyledons ( seed leaves at end of plumule ). The plumule is a term for the the growing tip of the epicotyl. The seed contains enough food to feed the plant inside through germination and the first few weeks, at least, of it’s life.
Plants have come a long way over time and developed many attributes to help them grow. Food storage tissue or nutritive tissue in the seed is one of those attributes. This tissue stores carbohydrates along with fats, oils and proteins to feed young plants. It is found in the endosperm, perisperm and cotyledons. The endosperm is tissue that is found inside the embryo sac inside the seed. The endosperm can be developed in many different ways. From smooth to mealy to hard and even as a liquid. The cotyledons are the first seed leaves and can store food for the embryo but also aid as a food source once the plant germinates. The perisperm is storage tissue that is only found in a few plant families. It is usually digested by the endosperm during seed development. Thus making it food for the food storage tissue.
Now that we have all these parts inside of our seed we need a way to protect them. This brings us to the seed covering. Seed coverings are on the outside of the seed and are usually hard and at least partially impermeable to water. This helps to keep water inside the seed and insect or fungal damage out. The seed covering consists of two parts the outer shell which is hard and thick and the inner shell which is thinner and more delicate. Hard outer coverings can cause seed dormancy so that the plant will germinate once growing conditions become favorable. The seed covering comes from the female sex organs of the plant. It is made up of parts of the nucellus and the endosperm. The nucellus contains the embryo sac. As the seeds mature they can swell and become dark in color. Sometimes exhibiting striations or stripped patterns. They can also exhibit other physiological characteristics from hairy to winged. These attributes can all play into a seeds success to germinate.