The seed catalogs have been arriving and gardeners are planning their vegetable gardens. This is the time to think about seeds – little powerpacks of plant embryos and food stored in protective containers.
During the process of seed germination, enzymes break down storage material and the embryo grows into a seedling. Different types of seeds require varying temperatures to germinate.
What is a seed?
A seed is a mature fertilized ovule (in gymnosperms) or an embryo enclosed in or attached to a food store tissue (endosperm in angiosperms) that grows into a new plant under the right conditions. Seeds have special mechanisms that allow them to delay growth until they encounter the favorable conditions for germination.
Often seeds are protected by a hard shell or fruit and some have specialized structures to aid in dispersal, such as dandelion puffs and the feathery pappus of Spanish-needle trees. Other seeds are carried a long distance by wind, birds, animals, or water, such as the barbed achenes of seaweeds and the wing-like appendages of some ferns.
Seeds come in many shapes and sizes, but all have several things in common. Most have a protective seed coat, some stored food, and an embryo that develops into a seedling when grown under the right conditions. Other key features are a hilum, or scar where the embryo was attached to the fruit; a micropyle, through which it can absorb water and nutrients; and an endosperm that contains starch as food for the embryo.
What are the main parts of a seed?
Seeds are an essential part of the reproductive cycle of flowering plants. They contain the embryonic stage of a plant, food reserves and other components necessary for growth. Seeds are found in a wide variety of shapes, sizes and colours. They are in a dormant state until the right conditions are present for germination, which is the process of growing a seed into a mature plant.
Seeds consist of three main parts – the seed coat, endosperm and the embryo. The seed coat protects the other parts of the seed, while the endosperm contains nutrients for growth.
The embryo is the young plant that develops from a fertilized egg. It is surrounded by the cotyledons and the radicle, which are the first two leaves of a seedling plant. It is also important to note that seeds can differ in shape and structure depending on whether they come from a monocot or dicot plant. Monocots have one cotyledon, while dicots have two cotyledons.
How do seeds grow?
Seeds have a lot to do in order to turn into new plants. They have to survive in a range of environments and conditions, grow into the right shape, sprout, and mature. They also need to be able to reproduce themselves.
Seeds look inactive and dead on the outside, but inside they are active, staying alive and waiting for conditions that will permit growth to start. As they lose water through their outer seed coat, they swell up (imbibe). This process is slow and requires the right temperature to initiate.
As the imbibition process continues, enzymes within the seed hydrate, triggering germination. The embryonic plant grows from the seed, sprouting a rudimentary root, stem, and leaf-like structures (cotyledons). The food stored in the endosperm provides nourishment until the embryonic plant can begin making its own food through photosynthesis. Seeds are packed with genetic information, and if the seed is open pollinated or is from an heirloom variety, the new plant will grow true to type.
Where can I find seeds?
If you have a passion for gardening, there are many places to buy seeds. Some online retailers specialize in heirloom varieties and are well-known for their beautiful seed catalogs. Others offer a wide range of non-GMO options and ship across North America.
The Seed Savers Exchange in Decorah, Iowa, helped launch the heirloom movement and maintains a seed bank with rare and heirloom varieties of flowers, vegetables, and herbs. You can order their seeds on their website or at select retail locations in the U.S.
Territorial Seed Company is another seed company that specializes in heirloom varieties and has taken the Safe Seed Pledge. Their website offers a wide variety of vegetable, herb, and wildflower seeds that are sure to please any gardener.
If you’re looking for an organic option, try the online retailer Botanical Interests. Their seeds are properly packaged and their website is easy to navigate. They also offer discounts and sales throughout the year.
