The Early Growth of a Plant From a Seed

Seeds

• Seeds contain almost everything a plant needs to go from its dormant stage to a young seedling. The seed coat protects the dormant seedling during conditions that would not be good for a small emerging plant. Sometimes the seed is dormant for years. Seeds can be buried in the soil so deeply that the sun doesn't reach them. The seed coat won't break down until something disturbs the soil and brings the seed close enough to the surface that the sunlight affects it. The coat also protects the seedling during cold or dry weather, not breaking down until conditions are just right. Once the proper conditions occur, the seed coat allows water through and softens along the edges.

Water

• Water is the one ingredient that seedlings need from outside the seed to begin growing. Water soaks through the seed coat and is absorbed by the tiny plant curled inside. In spring, when water is generally more plentiful, the seedling can absorb enough water in the first stage of germination to push the two halves of the seed coat apart, which allows the seedling to emerge -- root first.

Cotyledons

• There are two types of seed plants: monocots and dicots. Monocots -- such as grasses and irises -- have only one seedling leaf when they emerge. Dicots -- such as tomatoes and oak trees -- have two seedling leaves when they break out of the seed. These seedling leaves are cotyledons, and they contain the stored energy that the female plant gave to each seed to use while it gears up to photosynthesize. After the seedling uses up the energy stored in the cotyledon -- and the plant has put out its first true leaves -- the cotyledon turns yellow and dries up, eventually falling off the seedling plant.

Growth

• Two types of growth occur in seedlings. Initially, all growth is elongation. The root elongates into the soil, where it begins to collect nutrients and water, while the stem of the plant stretches first to the surface of the soil and then beyond it, reaching for the light. Elongation doesn't require new cells to form; instead, it results from cells getting longer vertically, growing either up or down.

  The second type of growth -- meristematic growth -- requires more energy and nutrients and involves cells dividing from undifferentiated cells found in buds that are located at the nodes of the plant, where leaves emerge. The distance between the nodes increases during elongation but does not change during meristematic growth. There are also meristem regions found at the tips of the roots. The first true leaves grow from apical meristems.