Unformatted text preview: SI worksheet 3 – Chapter 36 Terms Leaf Primordia finger like projections along the side of the apical meristem. Gives rise to leaves. Mycorrhizae Mutualistic association between roots and fungus. The plant provides the fungus with carbohydrates and sugars while the fungus provides the plant with a greater absorption of water and mineral nutrients due to increased surface area. The fungus also supplies phosphates to the plants that the plant could not otherwise obtain easily on its own. Critical to the colonization of land by vascular plants. Water potential Determines the direction of water flow by osmosis. Water will always move to a location of higher solute concentration until equilibrium is reached. (from a region of higher water potential to lower potential) Bulk Flow Long distance transport of water & minerals. The movement of liquid in response to a pressure gradient. Long distance bulk flow takes place within tracheids and vessel elements of the xylem and the sieve-‐tube elements of the phloem. The absence of cytoplasm in these dead cells helps facilitate the easy bulk transfer. Casparian Strip A belt made of suberin: a waxy material impervious to water and dissolved minerals. This forces minerals moving to the vascular cylinder to cross a selectively permeable membrane of an endodermal cell before entering the vascular cylinder Proton pump Involved in short distance transport across a membrane. Requires ATP. Pumps protons (H+) out of a cell. This changes the concentration gradient of protons to higher outside the cell and lower inside the cell. Gives us a proton gradient. Other molecules like sucrose can take advantage of this high gradient outside the cell and use a cotransporter to move back inside the cell through simple diffusion (no ATP used). Aquaporins transport proteins that facilitate the transport of water molecules across plasma membranes. These channels affect the rate at which water moves osmotically across the membrane. Endodermis Boundary between cortex (external ground) tissue and the vascular bundle. Houses the casparian strip. Also prevents the backflow of water and minerals once they have passed through the endoderm. Stomata Openings in leaves that allow for the transfer of gas between the plant and the environment. Short Answer Compare and contrast the Apoplastic, symplastic, and transmembrane route. References the movement of water and minerals through the plant. Apoplastic route – water and solutes move along the continuum of cell walls and extracellular space Symplastic route – water and solutes move along the continuum of cytosol. Inside plant cells using the plasmodesmata Transmembrane route – water and solutes move out of one cell, across the cell wall, and into another cell How are root architecture and the acquisition of water and minerals connected? • Soil is the resource mined by the root system. The strong taproot systems of gymnosperms and Eudicots allow them to grow to great heights, while the fibrous root systems of monocots do not provide enough support to reach great heights. • Plants rapidly adjust the architecture and physiology of their roots to exploit patches of available nutrients in the soil. (Branch out in an area of high nitrate or release more nitrogen transporting proteins) • Roots from plants of the same species placed close together have been found to not compete with each other What is the driving force for the transport of water from the roots to the shoots and up the plant? Explain. Transpiration, or water loss from the plant. Water is evaporated from the top of the plant, creating negative water potential, drawing xylem sap up the tree. What is the cohesion-‐tension hypothesis? Transpiration provides the pull for the ascent of xylem sap and the cohesion of water molecules transmits this pull along the entire length of the xylem from shoots to roots. Hence, xylem sap is under negative pressure, or tension. Transpiration pull • Water exits the leaves through the stomata because the air is dryer outside the leaf than inside. The negative pressure potential created causes water to move up through the xylem. • Increased surface tensions pulls water from surrounding cell spaces and up through the plant. Adhesion and cohesion • Adhesion is the attractive force between water and polar molecules. And since cellulose is polar is makes it easier for water to adhere to the walls and climb up the plant. • Water is also very cohesive meaning that is binds to itself through H bonds and can pull itself up a plant too. These two combined draw water up the plant. Transpirational pull can only exist along a continuous chain of water molecules. The formation of a water vapor pocket, breaks this chain. More common in wide vessel elements than in tracheids. This is not permanent. ...
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