Question
Biology Question on Cell Biology
Which of the following helps in maintenance of the pressure gradient in sieve tubes?
A
Albuminous cells
B
Sieve cells
C
Phloem parenchyma
D
Companion cells
Answer
Companion cells
Explanation
Solution
Companion cells help maintain the pressure gradient in sieve tubes by actively loading sugars into the sieve tubes. This creates a higher solute concentration and thus a higher osmotic pressure in the sieve tubes, resulting in the movement of water into them and thus maintaining the pressure gradient for phloem transport.