. The botany of crop plants : a text and reference book. Botany, Economic. ROOTS 19 the plant through root hairs, which are found near the tips of the smallest rootlets. In reality, the root hairs are the ab- sorbing organs of a plant. When we pull up any common herbaceous plant, we observe, as a rule, a large number of hair-like rootlets as branches of larger roots. These fine "hair roots" are sometimes mistaken for root hairs. But, closer examination, in which a hand lens may be necessary, shows us that these hair roots are the bearers of root hairs. In fact, root hairs are found o
. The botany of crop plants : a text and reference book. Botany, Economic. ROOTS 19 the plant through root hairs, which are found near the tips of the smallest rootlets. In reality, the root hairs are the ab- sorbing organs of a plant. When we pull up any common herbaceous plant, we observe, as a rule, a large number of hair-like rootlets as branches of larger roots. These fine "hair roots" are sometimes mistaken for root hairs. But, closer examination, in which a hand lens may be necessary, shows us that these hair roots are the bearers of root hairs. In fact, root hairs are found only on the smallest and youngest rootlets. Root-hair Zone.—Root hairs do not grow along the full length of a rootlet, but occupy a definite zone, designated the root-hair zone. This is clearly seen in young seedlings, grown on moist filter paper. The root- hair zone appears as a white fuzzy coating. The root cap is free of root hairs. The length of the zone varies from a few milli- meters to several centimeters. The root- hair zone of seedlings grown in soil is plainly evident from the mass of soil particles held by the root hairs (Fig. 8). Each root hair in its growth flattens out over, and some- times partially surrounds, the soil particles with which it comes into contact, thereby forming a close connection with the water and solutes that form a thin film around each soil particle (Fig. 9). Furthermore, the root hairs become mucilaginous, and this, along with their partial sur- rounding of particles, explains the presence of the mass of soil particles that clings to rootlets in the root-hair zone. Root hairs are short-lived, persisting for only a few days or. Fig. 8.—Wheat seedling showing soil particles cling- ing to root hairs; note that the root cap is free of root Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemb
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