EVERYDAY SCIENCE

Detailed explanation-1: -Contractile roots are roots that pull the plant deeper into the soil. Lily bulbs are a good example, as each bulb is pulled a little further into the soil as additional contractile roots are developed each year. When a region of stable temperature is reached, the contractile roots quit pulling.

Detailed explanation-2: -Contractile roots are responsible for movement of the underground shoot part ofthe plant, e.g., a corm, a bulb, or a. rhizome. Movement of such organs must overcome soil resistance, and thus it depends on several soil parameters, e.g., soil. type, moisture, and mechanical stability (Froebe and Pütz, 1988).

Detailed explanation-3: -Contractile roots are thickened root structures that are capable of shrinking under harsh environmental conditions, like seasonal drought. As a plant grows, its roots grow deeper and deeper into the soil.

Detailed explanation-4: -Contractile roots (CRs) that pull shoots further down in the soil are a possible example of convergent evolution in two monocot families, the Agavaceae and the Asphodelaceae.

Detailed explanation-5: -A tap root system penetrates deep into the soil. In contrast, a fibrous root system is located closer to the soil surface, and forms a dense network of roots that also helps prevent soil erosion (lawn grasses are a good example, as are wheat, rice, and corn).