Sieve tubes of phloem tissue lack

• Explanation:
-Sieve tube elements are specialized cells in the phloem tissue responsible for transporting sugars throughout the plant.
-To maximize their efficiency in transporting materials, they lose many cellular organelles, including the nucleus, during their development.
-This lack of a nucleus means they rely on companion cells for metabolic support and regulation.

🔑Key Points:

✏️SIEVE TUBE:
-A sieve tube is a phloem tissue.
-These are the long tubular conducting channel. These are placed end to end.
-The transverse end walls of the sieve tubes are perforated. These perforated areas are called sieve plates.
-The sieve tube cell is a living cell even though it loses its nucleus at maturity.
-The sieve tube cells have a thin layer of cytoplasm and a large central vacuole.
-The sieve tube is controlled by companion cells.
-It is connected to the companion cell through phloem parenchyma by plasmodesmata.
-Sieve tubes help transport food from the leaves to the other parts of the plant.
-Sieve tubes are absent in gymnosperms. Instead, sieve cells are present in gymnosperms as well as in pteridophytes.