 |
Uptake of Water and Minerals in Vascular Plants
Most vascular plants live on land and obtain water from the soil through their roots. Water present in a film of moisture around soil particles may move into root hairs by osmosis. The millions of tiny root hairs together have a very large surface area for absorbing water into the epidermal cells results in a greater concentration of water molecules there than in the layer of cortex cells inside. Thus, water moves by osmosis into thee cortex. From there, movement of water continues across thee many cell layers of a root until the water finally enters the xylem.
|
Some water may enter a root without passing through cells. Instead of passage by osmosis, the soid water moves through spaces between root cells until it reaches the endodermis. The water then passes 6hrough the endodermis and into the xylem.
Mineral ions enter roots by diffusion, facilitated diffusion, or active transport. Some minerals are used in root or are simply stored there. Other minerals enter the xylem. The xylem of roots extends into the stem and to the leaves. Water and dissolved ions are transported upward through this pipeline.
แหล่งข้อมูล: BIOLOGY living system. Page 454.
|
|