Spring is Coming, Are Your Seed Ready? Part 2
Last time we talked about how seeds are unique from other forms of life and how the begin their germination process. This time let's look at how the seed stores the vital food needed to nurture the embryo that will grow into the plant we desire to have.
Some seeds have thin seed coats, like beans and after only a couple of hours soaking in water the coats can easily be removed. Within the naked seeds are two chambers or storage structures called the seed leaves or cotyledons, and if you carefully unfurl these seed leaves we can get a good look inside of what is the embryo. The embryo is the tiny plant that is awaiting the moment of its birth to begin its life as a plant. The embryo has everything that a parent plant has but just much smaller in scale, it has a root known as a radicle ("small root"), a short stem and even a pair of leaves with veins and all.
During germination the embryo grows into a seedling and begin to grow in hopes of finding water at the roots and light at the top of the stem. Both of these components are vital in plant health and sustainability.
The cotyledons play the role of food storage for the developing seedling. The size of the food-storage structures are vital in determining the depth at which a seed should be planted. If the seed is planted too deep, it will use up all of its supplies before it reaches the soil surface. You will find recommended seed planting depths on the packages your seeds come in but a general rule of thumb is to not bury a seed any deeper that the seeds longest dimension. It is better to plant them too shallow than too deep.
The Good Lord has supplied the seed with everything it needs to become a new plant, it simply waits on three vitally important components: an ample supply of water, optimum temperatures, and finally a friable and well aerated soil.
A seed may remain dormant for moths or even years and still remain viable. As long as the conditions are right: less than 2% of the seeds weight is water. It is the low moisture content that protects the seed from the damage caused by repeated episodes of freezing and thawing. With each freeze/thaw cycle that a seed is subjected to, if there is enough water, it will freeze and expand and in return shred the protoplasm apart making it impossible to germinate.
The length of time a seed can be considered viable varies with the species and also the condition of storage. In seed storage banks, low temp and low humidity conditions are best suited for long term storage and viability of seeds. Seeds that were in storage at the Natural History Museum in Paris germinated after being in storage for more than 200 years.
A seed can be likened to a sponge and has the ability to absorb water easily and actually double their original volume. When this increase in volume occurs, the seed coat splits and in turn allows more water to penetrate and be taken in by the embryo and the cotyledons and also allows the access to the atmosphere and oxygen which is vital in this process of development.
When the embryo has sufficient food available it starts to push its roots in to the soil to find water, nutrients and minerals and provide a solid anchor for the plant to develop upon. Next the stem or embryonic shoot does its job of pushing up through the soil to the sunshine. It is at this point that germination ceases and plant development takes over.