Question

Phloem in gymnosperms lacks:

• A. Both sieve tubes and companion cells
• B. Albuminous cells and sieve cells
• C. Sieve tubes only
• D. Companion cells only

Answer 1

The correct option is A Both sieve tubes and companion cells

Phloem is a complex permanent tissue and has more than one type of cell and functions as a unit.

The main conducting elements of the phloem are the sieve elements, which are of two different types: sieve cells and sieve tubes.

The phloem elements of angiosperms differ from gymnosperms.

Sieve tubes are present in angiosperms but absent in gymnosperms.

Gymnosperms have sieve cells. Unlike sieve tubes, the sieve cells of gymnosperms lack a sieve plate. Sieve plates are thin plates which separate the neighbouring phloem cells, and are perforated by tiny sieve pores.

The sieve tube elements of angiosperms are associated with companion cells. They maintain the pressure gradient in the sieve tube elements.

Companion cells are absent in gymnosperms. However, in gymnosperms, their function is taken over by specialised parenchyma cells called the albuminous cells.

Hence, option a is correct.