Lecture 16 BIO 311D 2nd Edition Outline of Last Lecture I How do plants transport water up the xylem II What controls stomata opening III Design an experiment Outline of Current Lecture I Stomata experiment what do we learn II Phloem loading and unloading how Current Lecture I Stomata experiment what do we learn Which would lead to expansion of guard cell and opening stomata K ions flow into guard cells These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II Phloem loading and unloading how Plants use phloem tissue to move sugar solutions from source to sink A Which type of phloem cell is specialized for transport of sugar solutions How can cells spend ATP to move water against its concentration gradient Phloem loading move sugar into phloem tissue at a high concentration Phloem loading is an active process using proton pumps to create a H ion gradient and a co transport protein proton sucrose symport to move sucrose into a cell against its concentration gradient Need a high concentration of H on the outside this is done through a proton pump Movement through the symport is powered through the H gradient B So how could sugars be unloaded from phloem Think of some ways to maximize transport of sugar from a phloem cell into sink cell Through the plasmodesmata does not required ATP a sucrose membrane transport protein go down it s gradient 1 2 3 4 5 6 Transpiration pulls water up xylem vessels Source cells load sucrose into phloem sieve tubes reducing their water potential So water is taken up from xylem vessels by osmosis Internal pressure differences drive the sap down the sieve tube to sink cells Sucrose is unloaded into sink cells And water moves back to xylem vessels
View Full Document
Unlocking...