The Mechanisms That Regulate the Loading of Sucrose from the Apoplast

question 26

Multiple Choice

The mechanisms that regulate the loading of sucrose from the apoplast to the sieve-tube members by sucrose-H⁺ symporters are not well understood.Of the following possible regulatory factors,which is least likely to be of direct importance?

• A)turgor pressure of sieve-tube members
• B)sucrose concentration in the apoplast
• C)density of direct cytoplasmic connections between companion cells and sieve-tube members
• D)number of available symporter protein molecules in the plasma membranes of sieve-tube members