Root hairs

Root hair cells, the rhizoids of many vascular plants, are tubular outgrowths of trichoblasts, the hair-forming cells on the epidermis of a plant root. That is, root hair cells are lateral extensions of a single cell and only rarely branched. Just prior to the root hair cell development, there is a point of elevated phosphorylase activity.

Root hair cells vary between 5 and 17 micrometres in diameter, and 80 to 1,500 micrometres in length (Dittmar, cited in Esau, 1965).

Root hair cells can survive for 2 to 3 weeks and then die off. At the same time new root hair cells are continually being formed at the top of the root. This way, the root hair coverage stays the same.

It is, therefore, understandable that repotting must be done with care, because the root hair cell~s are pulled off for the most part. This is why planting-out leaves the plant withered for some time.

The root system of a flowering plant consists of one or more main roots from which small rootlets branch. The ends of these rootlets are covered with a fuzz-like growth. An examination with a magnifying glass will reveal that the "fuzz" consists of many tiny projections called root hairs.

Locate a diagram that shows a young, growing root. The growing point, the meristem, is the area where cells are dividing rapidly and the root is increasing in length. At the tip of the root is the root cap, which is a rather loosely packed mass of cells. Root cap cells are scraped off as the root tip pushes its way down into the soil. Just above the growing point many of the surface cells bear slender processes known as root hairs. These root hairs serve to absorb water and dissolved mineral compounds from the soil. Water enters root hairs from the soil and moves to all parts of the plant. As the water enters and moves through the plant, it carries the dissolved minerals that the plant needs for growth.