Page 26 - Demo 1

The phloem is the main food-conducng ssue in vascular plants. The conducng
cells of phloem are sieve tube members and sieve cells. Both cells are
elongated, but they differ in the extent of perforaons between the cells, with
the sieve cells having smaller perforaons between cells. The sieve tube
members are arranged to form a connuous sieve tube, some of which contain
a cluster of pores in their end walls collecvely known as a sieve plate. Sieve
tube members may contain cytoplasm but no nuclei. Specialized parenchyma
cells known as companion cells occur regularly in associaon with sieve tube
members. The companion cells may also play a role in the transport funcon of
the phloem.

In addion to conducng cells, xylem and phloem also contain fibers
(sclerenchyma cells) and parenchyma cells. The parenchyma cells funcon in
storage, and the fibers offer support and some storage. The fibers in xylem are
used for the producon of paper.

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