Water Potential exam Flashcards
Water Potential exam
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Water Potential The potential energy of water to move between two environments, determined by solute potential and pressure potential. What drives the movement of water in plants? Water moves from areas of high water potential to areas of low water potential. Solute Potential (Ψs) The solute concentration relative to pure water; high solute concentration means low solute potential. What is the unit of measurement for water potential? Water potential is measured in megapascals (MPa). Pressure Potential (Ψp) The physical pressure on water, which can be positive or negative. What is the cohesion-tension theory? A theory that explains how evaporation creates negative pressure, pulling water upward through the xylem. Transpiration The process of water evaporation from plant leaves, which helps pull water up from the roots. What is turgor pressure? The pressure inside a plant cell due to water pushing the cell contents against the cell wall. Casparian Strip A waxy layer in plant roots that regulates ion flow and solute concentration by blocking the apoplastic route. How do plants transport sugars? Sugars are transported from sources to sinks via bulk flow in the phloem, facilitated by pressure differences. Aquaporins Channels in cell membranes that facilitate the efficient movement of water. What is the role of the Casparian strip? It forces water into endodermal cells, allowing them to act as filters to control ion flow and solute concentration. Bulk Flow The movement of molecules along a pressure gradient, such as the movement of xylem sap or phloem sap. What is the photosynthesis-transpiration compromise? The balance plants must find between conserving water and maximizing photosynthesis. Root Pressure Theory A theory suggesting that positive pressure builds up in the root xylem due to increased water absorption relative to transpiration. What is the function of stomata? Stomata control gas exchange and water evaporation by opening and closing. Symplastic Route The pathway through the cytosol of cells, linked by plasmodesmata, for water movement. What is the role of proton pumps in phloem loading? Proton pumps create a proton gradient that allows the proton-sucrose symporter to load sugar into the phloem. Translocation The bulk flow of sugars from source to sink in the phloem. What is guttation? The exudation of water droplets from leaves due to high root pressure. Surface Tension The force between water molecules at the air-water interface, creating a tension across the surface. What is the main driving force for water movement in the xylem? The cohesion-tension theory, where evaporation creates negative pressure that pulls water upward. Phloem Loading The process of sugars entering the phloem via secondary active transport. What is the significance of lignified cell walls in vascular tissue? Lignified cell walls provide structural support to withstand the negative pressure generated by water transport. Capillary Action The ability of water to move through narrow spaces due to adhesion, cohesion, and surface tension. What is the role of the xylem? The xylem transports water and dissolved minerals from the roots to the rest of the plant. Photosynthesis-Transpiration Compromise The balance between conserving water and maximizing photosynthesis in plants. What is the pressure flow hypothesis? A theory explaining the movement of phloem sap from source to sink due to pressure differences. Cohesion The attraction between like molecules, such as water molecules clinging to each other.