Curriculum

WHERE IT ALL BEGINS

Seeds

When holding a seed in the palm of your hand, it may not seem to be capable of anything spectacular. However, every gardener knows how very much alive seeds actually are, just waiting patiently to be put in the right home with plenty of water and sunlight. Every seed shares the same anatomy, consisting of features needed to survive during their long “sleep.” To begin with, a seed is protected by the seed coat—a hard outer coating that protects the inner embryo from the outside world. Stored inside the seed coat is the embryo, which houses all of the cells the seed needs to develop. Also located inside the seed is the endosperm, which contains the food that the sleeping seed needs to remain viable.

Water is the element needed to wake seeds out of their rest—as soon as a seed comes in contact with moisture it will begin the process of germination. Germination marks the point at which seeds begin to live, taking nutrients from the soil to generate the energy needed for the first shoots and roots to sprout. While some plants need only moisture to begin germination, others require specific temperature conditions. This is why it is important to pay attention to growth specifications of various seed varieties when planning a planting schedule for a specific location and season.

The first part of the plant to emerge from the seed coat is the primary root, or radical, which grows downward into the soil. The root anchors the seed firmly in the earth and begins to absorb the water and nutrients that the plant needs to grow. Soon afterwards, the plumule, a stemlike shoot, sprouts from the seed and starts growing upwards through the earth towards the light. Once this stem emerges above ground, the germination stage is over and the plant will be able to turn the sun’s energy into food through the process of photosynthesis.

One of the most exciting parts of planning a garden is choosing spring seeds! The information printed on a seed packet provides direct clues about a seed’s needs, but the size, shape, and texture of the seed itself also helps to tell its story. These external characteristics of a seed point to how these seeds were originally dispersed and dropped into the soil. Seeds of trees that rely on wind for dispersal often have wings or long feathery tails that enable them to “fly” long distances. Other seeds are light and fluffy, allowing them to drift off in the slightest breeze. The dandelion is a great example of such a plant. Plants that live in or near water often depend on water to transport their seeds. As such, these seeds are usually very light and buoyant. The coconut tree is known for the amazing ability of its fruit and seed to travel extensive distances by floating in the ocean until washing ashore. Nature ensures that animals will be lured to a plant’s seeds by embedding the seeds within delicious fruit and berries. The animals that consume this fruit either bury the seeds in the soil (think of squirrels burying acorns) or eat them and then deposit them back into the soil after digestion.

WHAT IS A SEED?

A seed marks the first stage in the life of every plant. Stored safely inside the seed are all the components a plant will develop as it grows:

  • The plumule develops into the stem.
  • The radicle develops into the root.
  • The cotyledon is the seed leaves where food is stored.

Over time, seeds have developed these unique characteristics in order to adapt to the ecology of their habitat and to ensure the highest possible chance of dispersal. Today, humans have become one of the most important agents of seed dispersal for vegetable and fruit crops. By saving the seeds of the plants we grow each year and sowing them in the ground the following spring, we are ensuring the future survival of these plant species. Some crops actually depend on humans for germination—without humans to manually pollinate them, these plants species would be unable to produce successful offspring. Most of the crops that rely on humans are those that have been genetically altered—meaning that their genes have been manipulated in a laboratory in order to introduce some desirable trait. Examples of “desirable traits” include resistance to pests, better ability to survive in adverse environmental conditions, resistance to chemicals, or the expression of specific nutrients. Scientists have already begun to find that these genetically altered crops can be detrimental to the health of pollinator populations, such as bees and butterflies, which do not have the proper biological adaptions to digest the nectar from these species. (Sources: Loewer 1995, Davis 2008)

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