Germination can be thought of as the expansion from a small life form into a greater, more complex organism.
To master the process of seed germination, one must understand the anatomy of a seed and the biological process that takes place during germination.
What is a seed?
The simple components of a seed are:
Embryo. The ovule of a female flower develops into an embryo after fertilization. The embryo is essentially a tiny plant, whose basic components are a set of cotyledons (the very first set of leaves on a seedling) a plumule (what will become the shoot) and a radicle (will form the primary root, also referred to as a taproot)
A tissue that contains all the nutrients the seed will need to germinate typically surrounds the embryo itself. This food storage tissue, known as the endosperm, is what makes many seeds such a nutritious and wholesome part of our diet (think of the white fleshy inside of a coconut, the starchy consistency of rice, or the meaty, rich and protein-packed body of an almond or macadamia nut.
The embryo and endosperm are enclosed in a protective cover, known as the seed coat.
The seed coat develops from tissue from it’s mother plant, it’s job is to protect the embryo and its nourishing food source from external conditions until the time s right to sprout. Some examples of a seed coat are the papery skin around a raw peanut, or the hard outer husk of a coconut.
Coming to life
A seed is basically in a dormant state until it is placed in the right conditions.
When the external conditions become ideal, they send a signal to the unborn plant that it’s time to wake up. When this signal is received, germination begins and the
embryo resumes growth. The main external forces a seed needs to germinate are a temperature, moisture, and darkness.
When a seed is moistened by water, it slightly swells, breaking the seed coat. When moisture permeates into the inner seed, it activates enzymes that begin to break down the food stored within the endosperm. By the time the seedling has emerged from the seed coat and starts growing roots and leaves, it has used all of its food reserves and will depend on light, water, and nutrients for the energy needed to continue growing.
It’s important for the seed to have the right amount of oxygen to complete the process. If the soil is too soggy, or the seed is placed to far from the soil surface, it cannot metabolize its food source properly and will become starved. This is why many “seedling mix” soils have a light, fluffy body to them.
Different species of plants require different soil temperatures during germination. Most conmen annual vegetables and herbs have optimal germination temperature of 75-90 f, although many cool season crops can tolerate much lower soil temps.
Stay tuned for our next posting on different methods of germination, and tips to get your young seedlings started off right.
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