Root Functions

What are the different functions of roots?

How does a root go about the job of absorbing water and minerals from the soil? Although it might seem to, water does not just “soak” into the root from soil. It takes energy on the part of the plant to absorb water. Roots support a plant, anchor it in the ground, store food, and absorb water and dissolved nutrients from the soil.

Uptake of Plant Nutrients An understanding of soil helps explain how plant roots function. Soil is a complex mixture of sand, silt, clay, air, and bits of decaying animal and plant tissue. Soil in different places contains varying amounts of these ingredients. Sandy soil, for example, is made of large particles that retain few nutrients, whereas the finely textured silt and clay soils of the Midwest and southeastern United States are high in nutrients. The ingredients define the soil and determine, to a large extent, the kinds of plants that can grow in it.

To grow, flower, and produce seeds, plants require a variety of inorganic nutrients in addition to carbon dioxide and water. The nutrients needed in largest amounts are nitrogen, phosphorus, potassium, magnesium, sulfur, and calcium. The functions of these essential nutrients within a plant are described in Figure 23–7.

In addition to large amounts of these nutrients, small amounts of other nutrients, called trace elements, are just as important. These trace elements include iron, zinc, molybdenum, boron, copper, manganese, and chlorine. As important as they are, excessive amounts of any of these nutrients in soil can also be poisonous to plants.

FIGURE 23–7 Important Plant Nutrients Soil contains several nutrients that are essential for plant growth. Interpret Tables If you notice that a plant is becoming paler and more yellow, what nutrient might it be lacking?

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