Explain how dissolved sugar is transported in the phloem by means of a pressure gradient. What will be an ideal response?
Concepts to Consider: At the source, a proton pump moves H+ out of sieve tube members, causing
active transport of sugar into sieve tube members. Water moves by osmosis into sieve tubes, and
hydrostatic pressure increases inside them. At the sink, sugar is transported out of sieve tube members,
with water following. Thus, hydrostatic pressure decreases within the sieve tubes from source to sink.
Hence, sugar moves between the source and sink as it flows along the pressure gradient.
You might also like to view...
Which of the following best defines microevolution?
A. Changes across species but not in genes B. Changes in genes between populations C. Changes in genes within a population over time D. Changes in genes that do not change the gene pool over time
In DNA, complementary nitrogen bases are held together by
A. phosphodiester bonds. B. hydrogen bonds. C. peptide bonds. D. hydrophobic bonds. E. nitrogen bonds.
During prophase, the structure condenses and the nuclear membrane starts to break down. What are the two halves of the structure called?
A) sister chromatids B) chromosomes C) chromatin D) daughter DNA
Which of the following statements is correct about passive diffusion?
A) It requires an expenditure of energy by the cell. B) It is a process in which molecules move from a region of higher concentration to a region of lower concentration (or down a concentration gradient). C) It is a process in which molecules move from a region of lower concentration to one of higher concentration (or up a concentration gradient). D) It may require a transport protein. E) It involves movement of molecules down a concentration gradient and may require a transport protein.