Question 66

Mark every accurate description of the vessels that make up xylem. Select all that apply.

Each vessel is one living cell that pumps water upwards
The cells that form them are deadCorrect answer
They are hollow, so nothing inside obstructs the flowCorrect answer
The cells are joined end to end into a continuous tubeCorrect answer
Each vessel is kept full of cytoplasm by a living neighbour

Explanation

A xylem vessel is a file of cells that die and lose their contents, which leaves an open pipe that water can move along without crossing anything living. The idea that a transport tissue must be alive, or that a living neighbour keeps each vessel topped up with cytoplasm, fails on the same point: contents of any kind would obstruct the water column, and it is the sugar-carrying tissue that stays alive to do its very different job.

Explanation

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