An important feature of the rhizodermis are the root hairs that absorb water and nutriments. They originate in a zone with high cell division activity. They are arranged at a regular pattern on the surface of the rhizodermis. The oldest hairs are the longest, while those nearest the root tip are shortest. There are many root hairs, which are tubular extensions of the epidermis, in rice roots.
Root hairs increase the absorbing surface of the root.
This is important in transpiration and growth of the plant. They are highly vacuolate when fully differentiated. The formation of root hairs helps to increase the size of the absorbing root surface drastically. The roots have 14 milliard living root hairs with a surface totalling 400 km 2 . The surface of roots and root hairs thus sums up to 635 km 2 .