- please explain me the pathway of water in a plant or conduction of water.
Pathway of water in a plant
Roots of plants help in absorbtion of water and minerals from the soil. After absorbtion by roots, water and minerals are transported upward to other parts of plants through vascular tissue called xylem. Vascular tissue forms a network of channels that connects the root to the stem and the leaves of the plant.
Absorbtion of water by roots
Root hairs are thin-walled slender extensions of root epidermal cells that greatly increase the surface area for absorption. Water is absorbed along with mineral solutes, by the root hairs, purely by diffusion. Once water is absorbed by the root hairs, it can move deeper into root layers by two distinct pathways:
• apoplast pathway
• symplast pathway
The water then moves further reach the cells of the xylem in vascular cylinder.
Water Movement up a Plant
Now water has to move up against gravity. Two forces responsible for transporting the water up in a plant are root pressure and transpiration pull.
- Root pressure - Positive pressure created inside the xylem when water follows the ions transported along the concentration gradients into the vascular system.
- Transpiration pull- Pull of water as a result of tension created by transpiration is the major driving force of water movement upwards in a plant. (cohesion − tension transpiration pull)
Transpiration is the process by which excess water in plants is lost to the atmosphere in the form of water vapours through tiny pores present on the surface of the leaf called stomata. Transpiration pull helps in creating a suction pull to bring water from the root to leaves. This can be explained as follows: In actively growing plants, water evaporates continuously from the mesophyll cells of the leaf creating a negative pull. The lost water in the mesophyll is replaced by the absorption of water from the adjacent cells. Now water starts to pull through xylem vessels of leaves. Xylem vessels of leaves pulls water from xylem of stem which take water from Xylem of roots. Thus, water flow in a channel. This water channel is held together by cohesion force (force of attraction between water molecule). Adhesion (force of attraction between water molecules and walls of cells) and keeps the water column in the place. When water moves into the xylem, more soil water is drawn in the root. This inward movement due to transpirational pull will continue until the soil becomes excessive dry.
the XYLEM is the pathway for the conduction of water in the plants..this is showed by the experiment called....Balsam plant experiment.
In this experiment...the balsalm plant's root is cut down and the stem with the leaves is imersed in a beker containig colored water..(either water with few drops of eosin solution...or water with ink)...After a few hours...the stem of the plant is observed and the stem appears to be bluish or reddish(depending on the color added to the water). A thin section of the stem is taken out and is observed under a microscope.......it could be observed that only the xylem vessels were colored...and not the phloem or other tissues........this proved that xylem vessels are the main pathway for the conduction of water in plants!
the root absorb water due to the negative tension caused by transpiration.