Question

The sieve tubes and companion cells are the exceptional feature of:
a. Gymnosperms
b. Angiosperms
c. Ferns
d. Pteridophytes

Answer 1

The tissues perform specialized functions which are specific to those types of cells. Plants also have specialized cells or tissues that perform specific functions. Those tissues are divided into two groups: meristematic tissue and permanent tissues.

Complete answer: The meristematic tissues are the specialized tissues which have actively dividing cells present in the region of active cell division called meristems. Some cells in plants lose their ability to divide and these are termed as permanent tissues. These are also of two types: simple and complex.
-Simple permanent tissues are present mainly in leaves, stems, and mature roots. The complex tissues are those which have specialized cells that are made of more than one type of cells but work as a single unit. These are xylem and phloem; xylem is the tissue that is responsible for the conduction of water, mineral and nutrients from roots to the other parts of the plant body whereas phloem transports the food to the various tissues of the plant.
Xylem is composed of four types of tissues: tracheids, vessels, xylem fibers and xylem parenchyma. Similarly, phloem is also made up of four types of cells: sieve tube elements, companion cells, phloem parenchyma and phloem fibers. All these four elements are exceptionally well developed in angiosperms as these are the most advanced ones. Whereas, gymnosperms have albuminous cells and sieve cells. Gymnosperms and lower plants such as Pteridophytes, mosses and ferns lack sieve tubes and companion cells.
Therefore, the correct answer is option b- angiosperms.

Note: The Pteridophytes are the first successful terrestrial plants, but these do not have a well-developed ground tissue system. Ferns which are a type of pteridophyte possess vascular bundles but lack sieve cells and companion cells (a component of phloem tissue).