Briefly explain the transport of water and minerals in plant
Answers
Plants have two systems for the transportation of substances - using two different types of transport tissue. Xylem transports water and solutes from the roots to the leaves, while phloem transports food from the leaves to the rest of the plant. Transpiration is the process by which water evaporates from the leaves, which results in more water being drawn up from the roots. Plants have adaptations to reduce excessive water loss. Phloem transports synthesized food from the leaves to the rest of the plant body.
Water from the roots is pulled up by this tension. At night, when stomata close and transpiration stops, the water is held in the stem and leaf by the cohesion of water molecules to each other as well as the adhesion of water to the cell walls of the xylem vessels and tracheids.
Ascent of Sap:
The transport of water arid dissolved mineral salts from the roots to the leaves is known as ascent of sap. The cell wall of each root hair is permeable to water and minerals, but its cell membrane and the membrane around the vacuole are semi permeable membranes. The root hair cells take up mineral ions by active transport.
This creates a concentration difference of these ions between the root and the soil. Now, the soil solution has higher water content than the cell sap of the root hair. Hence, water from the soil diffuses into the root hair. The root hair cells now become turgid, while the adjacent cells of the cortex have lower water content.
This results in the diffusion of water from the root hairs into the cortical cells (Figure 3.1). After passing through the cortical cells by osmosis the water reaches the endodermis (tissue separating the cortex from the vascular tissues). The endodermis forces water into the xylem tubes through passage cells.
Water from the roots is pulled up by this tension. At night, when stomata close and transpiration stops, the water is held in the stem and leaf by the cohesion of water molecules to each other as well as the adhesion of water to the cell walls of the xylem vessels and tracheids.
Ascent of Sap:
The transport of water arid dissolved mineral salts from the roots to the leaves is known as ascent of sap. The cell wall of each root hair is permeable to water and minerals, but its cell membrane and the membrane around the vacuole are semi permeable membranes. The root hair cells take up mineral ions by active transport.
This creates a concentration difference of these ions between the root and the soil. Now, the soil solution has higher water content than the cell sap of the root hair. Hence, water from the soil diffuses into the root hair. The root hair cells now become turgid, while the adjacent cells of the cortex have lower water content.
This results in the diffusion of water from the root hairs into the cortical cells (Figure 3.1). After passing through the cortical cells by osmosis the water reaches the endodermis (tissue separating the cortex from the vascular tissues). The endodermis forces water into the xylem tubes through passage cells.
The pressure with which water is pushed into the xylem tubes of the root is called root pressure. The water moving upwards forms a column, which is maintained up to a certain height due to root pressure.
