An elongated, food-conducting cell in phloem in angiosperms. Unlike the tracheary elements of xylem, sieve elements have living protoplasts when mature, but they lack a nucleus and are dependent upon companion cells for certain functions. At the ends of each sieve-tube element are sieve plates, areas of the cell wall containing numerous large pores. The sieve-tube elements are aligned end to end and form continuous tubes, along which nutrients flow relatively unimpeded from cell to cell through the sieve plates. Sieve-tube elements are more specialized than the sieve cells found in gymnosperms. Compare sieve cell.
TAKE THIS QUIZ TO SEE WHAT YOU KNOW ABOUT HIGH SCHOOL PUNCTUATION!
Commas mark divisions in sentences. Periods end declarative sentences. Apostrophes show possession. Easy, right? Well, punctuation can get pretty tricky—fast. Think you got what it takes to be a punctuation expert? Take our quiz to prove it!
Question 1 of 10
Which of the options below is the best punctuation for the sentence? It__s your turn to pick the movie __ but your sister gets to pick the board game we _ re going to play.
Its your turn to pick the movie but your sister gets to pick the board game we’re going to play.
It’s your turn to pick the movie but your sister gets to pick the board game were going to play.
It’s your turn to pick the movie, but your sister gets to pick the board game we’re going to play.TAKE THE QUIZ TO FIND OUT
Words nearby sieve-tube element
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.