AP BIOLOGY

Detailed explanation-1: -Phloem is composed of sieve tube elements, companion cells, phloem parenchyma and phloem fibres. sieve tubes are longitudinally arranged cells. It is seen associated with the companion cells.

Detailed explanation-2: -In order to generate a tube system of low resistance, sieve elements loose most of their cellular components such as nucleus, cytoskeleton, ribosomes, tonoplast etc. during ontogeny. Mature sieve elements contain structural phloem specific proteins (P-proteins), mitochondria, ER, and sieve elements plastids.

Detailed explanation-3: -Phloem is the vascular tissue in charge of transport and distribution of the organic nutrients. The phloem is also a pathway to signaling molecules and has a structural function in the plant body. It is typically composed of three cell types: sieve elements, parenchyma, and sclerenchyma.

Detailed explanation-4: -phloem, plant vascular tissue that conducts foods made in the leaves during photosynthesis to all other parts of the plant. Phloem is composed of various specialized cells called sieve elements, phloem fibres, and phloem parenchyma cells.

Detailed explanation-5: -Sieve tubes and companion cells are components of xylem tissue.