Question

Phloem in gymnosperms lacks?

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

Answer 1

The correct option is D

Both sieve tubes and companion cells

The correct option is D.
The explanation for the correct option:

1. In vascular plants, the living tissue known as phloem carries photosynthates, or soluble organic molecules produced during photosynthesis, to the rest of the plant, particularly the sugar sucrose.
2. The sieve tube and the associated cells are absent from the phloem of gymnosperms.
3. Instead, they have sieve cells for the conduction of dietary materials.
4. The phloem conductive element is the sieve element.
5. Companion cells are cells that provide "life support" for the sieve's function.
6. Flowering plants have companion cells in their phloem.
7. They move amino acids and sugar in and out of the sieve components.
8. The transmembrane proteins are used by the partner cells in the leaf (the tissue of origin) for the active transport of amino acids and sugar.
9. The conducting component of the phloem is the sieve tube.
10. It is made up of vertical rows of elongated cells that are joined by holes in their walls in regions referred to as sieve plates.

Explanations for the incorrect options:
Option A:

1. Parenchyma cells that produce albumin are specialized cells.
2. In gymnosperm wood, they are discovered along with the sieve tube cells of the phloem.
   

Final answer: Phloem in gymnosperms lacks both sieve tubes and companion cells.