why and how does water enter externally into xylem of plants
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Hi there!
Water enters into the xylem of plants through roots.
Roots are further divided into small ones called as root hairs. These absorbs water from the soil. The water in that cell goes into neighbouring cell because of osmosis. And finally enters into xylem. And you may be wondering how water is going up to the tip of each leave.
The process helping here is TRANSPIRATION.
Transpiration is nothing but the evaporation of water. Transpiration creates a pull by which water comes up!. In this way the water does enter into the xylem.
See the pic.. Any doubts you can ask me.
:)
Water enters into the xylem of plants through roots.
Roots are further divided into small ones called as root hairs. These absorbs water from the soil. The water in that cell goes into neighbouring cell because of osmosis. And finally enters into xylem. And you may be wondering how water is going up to the tip of each leave.
The process helping here is TRANSPIRATION.
Transpiration is nothing but the evaporation of water. Transpiration creates a pull by which water comes up!. In this way the water does enter into the xylem.
See the pic.. Any doubts you can ask me.
:)
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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.
This is called the cohesion–tension theory of sap ascent.
The cohesion-tension theory explains how water moves up through the xylem. Inside the leaf at the cellular level, water on the surface of mesophyll cells saturates the cellulose microfibrils of the primary cell wall. The leaf contains many large intercellular air spaces for the exchange of oxygen for carbon dioxide, which is required for photosynthesis. The wet cell wall is exposed to the internal air space and the water on the surface of the cells evaporates into the air spaces. This decreases the thin film on the surface of the mesophyll cells. The decrease creates a greater tension on the water in the mesophyll cells, thereby increasing the pull on the water in the xylem vessels.
This is called the cohesion–tension theory of sap ascent.
The cohesion-tension theory explains how water moves up through the xylem. Inside the leaf at the cellular level, water on the surface of mesophyll cells saturates the cellulose microfibrils of the primary cell wall. The leaf contains many large intercellular air spaces for the exchange of oxygen for carbon dioxide, which is required for photosynthesis. The wet cell wall is exposed to the internal air space and the water on the surface of the cells evaporates into the air spaces. This decreases the thin film on the surface of the mesophyll cells. The decrease creates a greater tension on the water in the mesophyll cells, thereby increasing the pull on the water in the xylem vessels.
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