What is the structure of root hair cells?

Root hair cells are elongated, tubular structures that protrude from the surface of plant roots, with a large surface area for absorption.

Root hair cells, also known as trichoblasts, are specialised for the absorption of water and minerals from the soil. They are a type of epidermal cell, found on the outer layer of the plant root. Their structure is uniquely adapted to their function. They are elongated and tubular, extending out from the root surface into the soil. This shape increases their surface area, allowing for more efficient absorption of water and nutrients.

The cell wall of a root hair cell is semi-permeable, meaning it allows certain substances to pass through while blocking others. This is crucial for the cell's function as it allows water and mineral ions to enter the cell while preventing the loss of other important substances. The cell wall is also thin, which facilitates the movement of water and minerals into the cell.

Inside the root hair cell, there is a large vacuole filled with cell sap. This vacuole helps to maintain the cell's turgidity, which is important for the absorption of water. The cell sap inside the vacuole has a lower water potential than the surrounding soil water, which creates a water potential gradient. This gradient drives the movement of water from the soil into the cell by osmosis.

The cytoplasm of the root hair cell contains many mitochondria, which provide the energy needed for the active transport of mineral ions into the cell. This is necessary because the concentration of mineral ions is often higher inside the cell than in the soil, so energy is required to move these ions against their concentration gradient.

In summary, the structure of root hair cells – their elongated shape, large surface area, semi-permeable and thin cell wall, large vacuole, and numerous mitochondria – all contribute to their primary function of absorbing water and minerals from the soil.