How do rolled grass leaves reduce water loss in dry habitats?

In dry habitats, many grasses reduce water loss by rolling their leaves into long, thin tubes, which effectively decreases the leaf's surface area exposed to the environment.1

This rolling mechanism is facilitated by specialized cells in the epidermis known as bulliform cells (also called motor or hygroscopic cells). These large, thin-walled cells are sensitive to changes in turgor pressure; when water availability is low, the loss of turgor in these cells causes the leaf to roll inward. By forming a tube, the plant creates a microenvironment that helps inhibit transpiration and conserve moisture during periods of limited water.231