Exam 3 Notes


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Unformatted text preview: ylem Cohesion and Adhesion 27 o The transpirational pull is transmitted all the way from the leaves to the root tips and even into the soil o Faciliatated by cohesion and adhesion o www.youtube.com/watch? v=At1BJJDcXhk Pushing Xylem Sap: Root Pressure At night, transpiration is low, root cells still pump ions into xylem of vascular cylinder Lowers water potential and water flows into root cortex, generating root pressure Sometimes causes guttation in small herbaceous plants Transports water only over small distances The rate of transpiration is regulated by stomata The large surface area of leaves increases photosynthesis, but also increases water loss through stomata guard cells flank the stomata – regulate the amount of water in the plant Stomata: Major Pathways for Water Loss About 90% of water loss by a plant occurs through the stomata Water loss is regulated by guard cells that flank the stomata 28 Opening and Closing the Stomata The transport of K+ is coupled with H+ pumps H+ is pumped out setting up a membrane potential K+ moves into the cell following the membrane potential gradient Sugars are transported from sources to sinks via the phloem Translocation – the transport of organic nutrients in the phloem of a plant Movement from Sugar Sources to Sugar Sinks sugar source – plant organ that is a net producer or source of sugar (e.g., mature leaves) sugar sink – organ that is a net consumer or storage site of sugar (e.g., tuber or bulb during...
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