PLANT TRANSPORT Advanced Biology Chapter 22 NOTES

Absorption & Transport of Water & Minerals  Water is absorbed by osmosis mostly by root hairs. Root hairs greatly increase the absorptive surface.  The plasma membrane of the root cells control the uptake of solute.  Water absorbed goes through:  Symplast Pathway (through the cells)  Apoplast Pathway (between the cells)  Transmembrane Pathway (combination of both)  Once the water reach the endodermis, a continuous waxy barrier called Casparian strip stops them from entering the xylem, and force them to cross a selectively permeable membrane of endodermal cell to enter the xylem.  Water is absorbed by osmosis mostly by root hairs. Root hairs greatly increase the absorptive surface.  The plasma membrane of the root cells control the uptake of solute.  Water absorbed goes through:  Symplast Pathway (through the cells)  Apoplast Pathway (between the cells)  Transmembrane Pathway (combination of both)  Once the water reach the endodermis, a continuous waxy barrier called Casparian strip stops them from entering the xylem, and force them to cross a selectively permeable membrane of endodermal cell to enter the xylem.

Bulk Transport  Efficient long distance transport of fluid requires Bulk flow, the movement of a fluid driven by pressure.  Water and solutes move together through tracheid and vessel elements of xylem, and sieve-tube elements of phloem  Efficient movement is possible because mature tracheid and vessel elements have no cytoplasm, and sieve-tube elements have few organelles in their cytoplasm.  Plants can move a large volume of water from their roots to shoots  Efficient long distance transport of fluid requires Bulk flow, the movement of a fluid driven by pressure.  Water and solutes move together through tracheid and vessel elements of xylem, and sieve-tube elements of phloem  Efficient movement is possible because mature tracheid and vessel elements have no cytoplasm, and sieve-tube elements have few organelles in their cytoplasm.  Plants can move a large volume of water from their roots to shoots

Transpiration  Transpiration is the process by which water evaporates from a plant from leaves into the atmosphere.  Transpiration is influenced by weather conditions such as humidity, wind, light intensity, temperature and water supply.  Xylem sap consist of water and dissolved inorganic molecules.  The root pressure, accumulation of water in roots by osmosis can push the xylem sap up from the ground.  Transpiration can also move the xylem sap to the top of the tree, this is because the 2 special properties of water:  The overall process of the movement of xylem sap is called Transpiration-Cohesion-Tension Mechanism.  Root pressure sometimes result in guttation, the exudation of water droplets on the tips of the leaves.  Transpiration is the process by which water evaporates from a plant from leaves into the atmosphere.  Transpiration is influenced by weather conditions such as humidity, wind, light intensity, temperature and water supply.  Xylem sap consist of water and dissolved inorganic molecules.  The root pressure, accumulation of water in roots by osmosis can push the xylem sap up from the ground.  Transpiration can also move the xylem sap to the top of the tree, this is because the 2 special properties of water:  The overall process of the movement of xylem sap is called Transpiration-Cohesion-Tension Mechanism.  Root pressure sometimes result in guttation, the exudation of water droplets on the tips of the leaves.

Transport of Organic Substances  Phloem sap is an aqueous solution that is high in sucrose. It travels from a sugar source to sugar sink.  Sugar source is an organ that produce sugar, such as leaves.  Sugar sink is an organ that consume or store sugar, such as tuber or bulb.  Pressure Flow Mechanism is the flow of phloem sap from source to sink.  The sugar is loaded from the sugar source, increasing the concentration of sugar and water flow, raising the pressure  The sugar is removed to the sugar sink.  Organic substances such as sucrose and other molecules such as hormones are transported by the process of translocation, through the phloem.  Phloem sap is an aqueous solution that is high in sucrose. It travels from a sugar source to sugar sink.  Sugar source is an organ that produce sugar, such as leaves.  Sugar sink is an organ that consume or store sugar, such as tuber or bulb.  Pressure Flow Mechanism is the flow of phloem sap from source to sink.  The sugar is loaded from the sugar source, increasing the concentration of sugar and water flow, raising the pressure  The sugar is removed to the sugar sink.  Organic substances such as sucrose and other molecules such as hormones are transported by the process of translocation, through the phloem.