Exam 37: Water and Sugar Transport in Plants

Researchers have investigated bidirectional transport in phloem by applying different radioisotope tracers to two source leaves and monitoring a point between the two sources for the presence of the tracers.Which of the following observations would not support the pressure-flow hypothesis? Appearance of the two tracers in _____.

Researchers using a dendrograph found that the trunk diameter of a beech tree increased and decreased slightly on a daily basis and that this variation correlated negatively with transpiration rate.Under which of the following sets of conditions should the daily changes in trunk diameter be the highest?

As an undergraduate research assistant in the lab of the famous Dr.S.Nameerf,you are assisting with a radioisotope tracer experiment.You expose a mature leaf on one side of the lower shoot of a sugar beet plant to ¹⁴CO₂ and then track the movement of the ¹⁴C atoms by radiography.Where are you least likely to detect ¹⁴C?

Researchers using a dendrograph found that the trunk diameter of a beech tree increased and decreased slightly on a daily basis and that this variation correlated negatively with transpiration rate.Under which of the following sets of conditions should the daily changes in trunk diameter be the smallest?

Which of the following supports the finding that sugar translocation in phloem is an active (energy-requiring)process?

Formation of menisci,such as occur in a tube filled with water,is an important factor in plant water movement.A meniscus is created by _____.

Which of the following cross-membrane transport mechanisms requires the expenditure of energy?

Which of the following would be expected to contribute to relatively high rates of transpiration?

Loss of water from the aerial parts of plants is called _____.

The research by Natalie De Witt and Michael Sussman showed that proton pump AHA3 is localized in the membrane of companion cells of the source tissue.What is the function of this pump?

If you cut a stalk (petiole)of celery and place it in a beaker of water that has food coloring dissolved in it,colored water will move up the stalk and into the leaf blades.This provides evidence against which of the following theories of xylem transport?

Irrigation reduces soil quality and rains usually don't.Why?

The processes of water flow in xylem and sugar translocation in phloem differ in many respects.Which of the following is not a difference between xylem and phloem transport?

Which of the following is not a net sink for products of photosynthesis in a deciduous angiosperm tree?

Water potential in plants consists mainly of _____.

CAM and C₄ plants conduct photosynthesis in ways that allow them to live in drier areas than most C₃ plants can tolerate.The effectiveness of different plants in restricting water loss while still allowing for influx of adequate CO₂ can be compared using the transpiration ratio,which is calculated by dividing the amount of water transpired by the amount of CO₂ fixed by photosynthesis.If a typical transpiration ratio for a C₃ plant is 500,then possible values for CAM and C₄ plants could be _____.

Which of the following would not be expected to contribute to high rates of transpiration?

Which of the following statements about phloem unloading at sinks is not consistent with our current understanding?

Which of the following does not support the cohesion-tension theory of xylem transport?

Cell-to-cell water movement always occurs from _____.