Question

An organized and differentiated cellular structure having cytoplasm but no nucleus is:

• A. Xylem vessels
• B. Xylem parenchyma
• C. Sieve tubes
• D. Tracheids

Answer 1

The correct option is C Sieve tubes

The main function of phloem is to conduct food materials, usually from the leaf to other plant parts (e.g., storage organ and growing regions). Phloem consist of 4 types of cells:

1. Sieve cell (in gymnosperms and pteridophytes)/ Sieve tube (in angiosperms)
2. Companion cells
3. Phloem fibres/Bast fibres
4. Phloem parenchyma

Sieve cells/sieve tube element are living and thin walled. Mature sieve tube elements are enucleated living cells. Central vacuole is present in each sieve cells/sieve tube element and around the central vacuole thin layer of cytoplasm is present.

Mature xylem vessels and tracheids are made up of dead cells which lack a protoplasm.

Xylem parenchyma is made up of living cells possessing both cytoplasm and nucleus.