alleryStart learning →Phloem sap is an aqueous solution containing up to what percentage of sugar?
A10 percent
B20 percent
C30 percent
D50 percent
Answer & Solution
Correct answer: C. 30 percent
1. Phloem sap carries sugar along with minerals, amino acids and plant growth regulators.
2. Its sugar content runs up to 30 percent.
3. That high sugar concentration lowers solute potential and therefore total water potential in the sieve tube.
4. Water then moves by osmosis from the adjacent xylem into the phloem, raising the pressure that drives bulk flow.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.5 Transport of Water and Solutes in Plants_
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