AP BIOLOGY

Detailed explanation-1: -Companion cells, or albuminous cells in non-flowering vascular plants, are another specialized type of parenchyma and carry out the cellular functions of adjacent sieve elements; they typically have a larger number of mitochondria and ribosomes than other parenchyma cells.

Detailed explanation-2: -Companion cells showed a dense cytoplasm and various small vacuoles. They also revealed their characteristic large nucleus and abundant mitochondria.

Detailed explanation-3: -So, the correct answer is ‘It is present in all vascular plants having phloem’.

Detailed explanation-4: -Among other adaptations, companion cells therefore contain many mitochondria. This allows them to carry out cellular respiration at a high rate and, hence, release lots of energy.

Detailed explanation-5: -The companion cells have dense protoplasts which contain the typical organelles of plant cells, including chloroplasts and many ribosomes. The sieve elements and companion cells are interconnected by numerous branched plasmodesmata. The companion cells degenerate when the associated sieve elements cease to function.