Seed means “a miniature undeveloped plant with a supply of food reserves, wrapped in a protective coat.” Seeds can lie dormant for a very long time.
Some seeds require physical or chemical dormancy to break before they germinate. For example, a hard seed coating can be broken by soaking or scarifying (scratching the surface). Other seeds need physiological dormancy, which is ended by exposing them to cold and moist stratification.
What Are Seeds?
Seed is the characteristic reproductive body of both gymnosperms (conifers and cycads) and flowering plants (angiosperms). It contains a miniature undeveloped plant embryo and some stored food materials enclosed in a covering called a testa.
Seeds may entice animals to disperse them (sticky seeds, hooks and barbs on burrs) or have fleshy appendages that attract animals who will eat them (acai, mango, peach). Others have wings (pine, maple) for wind dispersal.
Seeds are long-term storable foods for animals and provide an important food source for birds, mammals, reptiles and fish. They are the primary sources of grains (wheat, corn, barley and rice), legumes (beans, peas and peanuts), some vegetables and spices like dill, cilantro and basil, and many cooking oils including soybean, rapeseed (“canola”), sunflower and coconut.
How Do Seeds Grow?
Seeds are living entities with a store of food reserves, an embryo and other cellular structures that provide energy for growth. Each seed species has its own germination requirements that must be met for the seeds to sprout.
All seeds require water to initiate germination. The hard, impermeable seed coats must be softened so water can penetrate and swell the embryo. In nature, this can happen when the seeds are worn down by rodents or crushed in a rock crusher, or if they swell after undergoing freezing and thawing, being eaten by animals, being blown around by winds or passing through an animal’s digestive system.
Soaking seeds in water, a process called leaching, removes chemical inhibitors that prevent germination. The soaking should be done for 12 to 24 hours. Many seeds–especially peppers, tomatoes and some perennials–also need a period of cold to break their dormancy.
What Happens to Seeds When They Sprout?
Seeds contain everything they need to grow into a new plant. The hardest part is getting them to “wake up.” The process of waking up and growing is called germination.
Inside a seed is an embryonic (baby) plant and a food supply packed in starchy cells called endosperm. As the embryo starts to sprout, it pierces its seed coat and goes looking for water. It may also go down to anchor itself or up to look for light.
When it finds water, the seed starts to absorb it. This is called imbibition. The seed’s cell walls start to expand, and the seed coat softens and wrinkles up. Then the embryo starts forming roots and a tiny leaf (or cotyledon) at its top, depending on whether the plant is a dicot or monocot.
How Do Seeds Reproduce?
Seeds are an important part of the reproductive process of many plants. Without seeds it would be very difficult to plant many of the flowers, grasses and ground cover, vegetables and some trees we enjoy. Seeds are also used to produce most of the food we eat including grains, beans and nuts. Seeds also provide important textile dyes.
Seeds are fertilized ovules of seed plants (gymnosperms and angiosperms) that contain embryonic plant material and a store of food, all surrounded by a protective coating called a testa. A well-developed seed is a fertilized ovule capable of growing into a new plant given the right growth conditions. It consists of one or two cotyledons or seed leaves, a nutritious endosperm and at its center the embryonic plant embryo.
What Are the Basic Parts of a Seed Embryo?
The basic parts of a seed are a protective seed coat, stored food and an embryo that’s the beginning of a new plant. Seeds come in a variety of shapes and sizes, but all seeds have the same basic parts.
The outer covering of a seed is called the seed coat or testa and protects it from predators, pathogens and dryness. It also inhibits germination under unfavorable environmental conditions.
Inside the seed coat is the embryo and either one or two cotyledons (seed leaves) depending on whether the seed is monocotyledonous or dicotyledonous. The cotyledons provide nourishment to the embryo during germination. The embryo has its own set of roots and a stem (plumule) that sprout as it grows. A protein-rich layer called the aleurone separates the cotyledons from the embryo.