What's Inside a Seed? All This


Who remembers this scenario?

It's kindergarten. Standing in a line next to the window, you and each of your classmates are holding a cup and wet paper towel. Your teacher hands you a little bean and helps you place the bean inside its damp cocoon. And every day you and your friends run to the window to see that exact moment that the bean has sprouted.

Do you remember the parts of the seed? How seeds are made? How to store seeds?  How to plant and take care of seeds? 

If not, here is a little primer for you. That wonder is still there - plus more than you may have imagined.

The Parts of a Seed

Isn't it amazing that some of the most dramatic changes to your plants happen before you even see them above the ground? Here's what's going on inside that unassuming little seed:

Seed Coat: This is the protective covering around the seed.

Endosperm: Food for the plant embryo to use until it sprouts and can produce its own food.

Plumule: This section will become the plant's shoot.

Cotyledons: “Seed Leaves”  These are the first little leaves that you see when the plant sprouts.  They are fully formed, inside the seed.

Hypocotyl: The stem of the plant embryo.

Radicle: The root portion of the embryo.  It pushes out and down to become a root, and breaks a hole in the seed coat so the cotyledons can push out and grow upward.

Hot (or Temperate) Enough For Ya?

Image: discoverexpresskids.com

While you may think growing seeds is a just-add-water sort of experience, in reality, the seed's first days are by no means guaranteed.

In general, for seeds to remain viable - able to grow under the right conditions - they need to be kept in an environment where the humidity and temperature levels equal less than one hundred degrees Fahrenheit. So for example, if the temperature is 60 degrees, the humidity should be no more than 40%. 

Even when they're not growing yet, seeds are alive - they are just metabolizing incredibly slowly.  And plants metabolize faster at higher temperatures.  Hence, there's a need to keep temperatures low when storing your seeds.

Humidity and/or water are also factors in helping the seed germinate.The combination of spring-like temperatures and water cause the shell of the seed to crack so that the seed can finally begin to grow. 

More Than "Just Add Water"

Image: wonderopolis.org

Remember that little science lesson about the parts of the seed? Here's where they finally begin to perform their magic.

The reason most seeds grow in spring, or during warmer times, is that they require both warmth and moisture in order to be activated into the growing process. They're dormant until then, as you've seen from the (possibly many) packets of dried, rather quiet seeds you may have stored in your shed right now.

Interestingly, seeds respirate, just like most living entities. Oxygen must be able to permeate the soil, and the carbon dioxide the seeds give off needs to have room to move away from the emerging plant. That's why correct aeration is so important and why it can be difficult to grow plants in very clay-like soil.

While seedlings will need sunlight (or proper artificial light), seeds like darkness in order to germinate. In a temperate, rather moist, dark location, the seed will start its fascinating process. Here's what happens:

Three Fascinating Steps to Your New Plant

1. Imbibition: The seed absorbs moisture and the coat begins to swell and soften.

2. Interim/Lag Phase: The seed is "activated" internally and begins metabolizing faster.

3. Emergence of the Radicle and Root: As the cells inside the seed divide and more room is taken up, the radicle and root emerge out of the seed.

After this point, the root grows downward, creating more roots (generally), and the plant will grow and emerge from the soil. This time period depends upon what it is you're growing. Some seedlings emerge and are visible within a matter of days.

Now you know the seed's most fascinating secrets. Treat your seeds and seedlings properly and they'll have a great foundation upon which to grow and produce at their most beautiful best!

Lead image: sciencing.com

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