Active non-osmotic water absorption: This theory was given by Thimann (1951) and Kramer (1959). According to the theory, sometimes water is absorbed against concentration gradient. This requires expenditure of metabolic energy released from respiration of root cells. There is no direct evidence, but some scientists suggest involvement of energy from respiration. In conclusion it is said that, the evidences supporting active absorption of water are themselves poor. Passive absorption: This mechanism is carried out without utilization of metabolic energy. Here only the root act as an organ of absorption or passage. Hence, sometimes it is called water absorption 'through roots', rather 'by' roots. It occurs in rapidly transpiring plants during daytime, because of opening of stomata and the atmospheric conditions. The force for absorption of water is created at the leaf end i.i. the The main cause behind this transpiration pull, water is lifted up in the transpiration pull. plant axis like a bucket of water is lifted by a person from a well. Transpiration pull is responsible for dragging water at the leaf end, the pull or force is transmitted down to the root through water column in the xylem elements. The continuity of water column remains intact due to the cohesion between the molecules and it act as a rope. Roots simply act as a passive organ of absorption. As transpiration proceeds, simultaneously water absorption also takes place to compensate the water loss from leaf end. Most volume of water entering plants is by means of passive absorption. Water Movement in Roots: Water in the roots move by two pathways. They can be classified as 1) Apoplast pathway 2) Symplast pathway Apoplast Pathway: In this pathway the movement of water occurs exclusively through cell wall without the involvement of any membranes. Majority of the amount of water goes through the apoplast pathway. The cortex of the root does not oppose such movement of the water. Symplast Pathway: Here the movement of water molecules is from cell to cell through the plasmodesmata. The plasmodesmata forms a network of cytoplasm of all cells
Active non-osmotic water absorption: This theory was given by Thimann (1951) and Kramer (1959). According to the theory, sometimes water is absorbed against concentration gradient. This requires expenditure of metabolic energy released from respiration of root cells. There is no direct evidence, but some scientists suggest involvement of energy from respiration. In conclusion it is said that, the evidences supporting active absorption of water are themselves poor. Passive absorption: This mechanism is carried out without utilization of metabolic energy. Here only the root act as an organ of absorption or passage. Hence, sometimes it is called water absorption 'through roots', rather 'by' roots. It occurs in rapidly transpiring plants during daytime, because of opening of stomata and the atmospheric conditions. The force for absorption of water is created at the leaf end i.i. the transpiration pull. The main cause behind this transpiration pull, water is lifted up in the plant axis like a bucket of water is lifted by a person from a well. Transpiration pull is responsible for dragging water at the leaf end, the pull or force is transmitted down to the root through water column in the xylem elements. The continuity of water column remains intact due to the cohesion between the molecules and it act as a rope. Roots simply act as a passive organ of absorption. As transpiration proceeds, simultaneously water absorption also takes place to compensate the water loss from leaf end. Most volume of water entering plants is by means of passive absorption. Water Movement in Roots: Water in the roots move by two pathways. They can be classified as 1) Apoplast pathway 2) Symplast pathway Apoplast Pathway: In this pathway the movement of water occurs exclusively through cell wall without the involvement of any membranes. Majority of the amount of water goes through the apoplast pathway. The cortex of the root does not oppose such movement of the water. Symplast Pathway: Here the movement of water molecules is from cell to cell through the plasmodesmata. The plasmodesmata forms a network of cytoplasm of all cells