This video from Curious George shows students helping bean seeds sprout outside of soil by meeting their essential needs for moisture, temperature, air, and light. The children place the beans and a wet paper towel inside a zippered plastic bag and leave them undisturbed in a warm, well-lighted place. After two weeks, the students return and observe that the beans have sprouted and, like apple seeds, will one day grow to be fully developed plants.
In general, most plants grow by absorbing water and nutrients from soil. Soil's nutrient content, texture, and acidity together determine whether the plant will be able to meet its life cycle needs. But soil is only important after seed germination has already occurred. Need proof? As this video demonstrates, seeds can sprout outside of soil, provided a few environmental conditions are met.
A seed is a tiny plant-in-waiting. Inside its protective coating are leaf, stem, and root parts just waiting to emerge. Germination marks the time when a plant starts to grow from a seed. The conditions that plants need for germination and growth vary among species. The most important ones are temperature, water, oxygen, and, to a differing extent, light. Seeds germinate over a wide range of temperatures. Some seeds will not germinate above or below a certain temperature. For example, seeds that grow in colder climates do not germinate until spring or early summer when the soil and air have warmed.
Germination also requires moist conditions. As seeds take in water, the swelling creates the pressure needed to crack the seed coat for germination. Once the seed coat is cracked, the germinating seedling needs oxygen for its metabolism. Moisture and oxygen levels are closely linked; if a seed gets too much moisture—as in flooded conditions—it may not get enough oxygen, and growth will not take place.
For certain plant types, light must be present in order for their seeds to germinate. Many seeds in forest settings, for example, will not germinate if sufficient light does not penetrate the canopy and reach the ground. Conversely, there are plants that need darkness in order for their seeds to germinate. Cactus and other desert plant seeds can only germinate in total darkness deep within the soil.
Once a seed has germinated and the root and shoot begin to grow, plants rely on nutrients to continue their growth. The sixteen chemical elements that are important to a plant's growth and survival are divided into two main groups: non-mineral and mineral. Non-mineral elements include hydrogen, oxygen, and carbon—nutrients found in air and water. Plants use these nutrients along with energy present in sunlight to produce their own food in a process called photosynthesis. Mineral elements come from soil. They are dissolved in water and absorbed by the plant through its roots. The primary nutrients are nitrogen, phosphorous, and potassium. When these minerals are missing from soil, farmers or gardeners wanting to grow crops or a small vegetable garden add them to the soil using natural or synthetic fertilizers.
Academic standards correlations on Teachers' Domain use the Achievement Standards Network (ASN) database of state and national standards, provided to NSDL projects courtesy of JES & Co.
We assign reference terms to each statement within a standards document and to each media resource, and correlations are based upon matches of these terms for a given grade band. If a particular standards document of interest to you is not displayed yet, it most likely has not yet been processed by ASN or by Teachers' Domain. We will be adding social studies and arts correlations over the coming year, and also will be increasing the specificity of alignment.