ROOT-HAIR STRUCTURE AND DEVELOPMENT IN THE SEAGRASS HALOPHILA-OVALIS (R BR) HOOK F

The seagrass Halophila ovalis normally produces one mature root, cover ed with a permanent mat of root hairs, per node. In this study, the de velopment of the root hairs increased the effective root surface absor ptive area by 215%. Of the root surface examined, 39% was devoted to r oot-hair production. Epidermal cells that produced root hairs containe d more cytoplasm, endoplasmic reticulum and Golgi bodies than did adja cent hairless cells. In addition to appearing to be more metabolically active, root-hair-producing cells had a greater number of plasmodesma tal connections with the underlying outer cortical cells than did adja cent cells that did not produce root hairs. This would suggest that ce lls that produce root hairs play a more active role in nutrient uptake and exchange than do other cortical cells.