Biology 9700 · AS & A Level · Movement into and out of cells

Movement into and out of cells — practice question

An aphid, for example a greenfly, feeds on nutrients in the plant by using a narrow tubular mouthpart known as a stylet. It pushes the stylet through the outer surface of a stem or leaf. If a stylet is cut close to the aphid’s head while the stylet remains in the plant, a liquid with a low water potential still keeps flowing out from the plant. Which statement accounts for this?

  • AThe stylet is in a phloem sieve tube element in which there is a high concentration of solutes.
  • BThe stylet is in a phloem sieve tube element in which there is a low concentration of solutes.
  • CThe stylet is in a xylem vessel element in which there is a high concentration of solutes.
  • DThe stylet is in a xylem vessel element in which there is a low concentration of solutes.

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