Internal structure of the root
A longitudinal cut of a young root shows five parts from the tip upward. At the very tip is the root cap, which protects the division zone. In the division zone cells of formative tissue divide constantly. In the growth zone above it the cells do not divide but stretch and enlarge, so the root grows longer. The absorption zone bears root hairs: each is an outgrowth of a surface cell and absorbs water and mineral salts from the soil; they live 10–12 days and new ones keep appearing nearer the tip. At the top is the conducting zone, where xylem carries water and salts up and phloem carries organic matter down. Roots also breathe, using the air between soil particles, which is why loosening the soil by hoeing is necessary. If the root tip is lost, lateral roots grow more strongly — farmers use this by pinching the root tip of seedlings before transplanting.
Observation: germinate wheat or radish seeds on wet filter paper. On day 3–4 view the root hairs with a magnifier and draw the root tip with its parts labelled. Extra question: why does soil stick to the root tip when you pull a seedling out? (The hairs cling to soil particles.) Safety: never look at the Sun through a magnifier.