AP BIOLOGY

Detailed explanation-1: -SIEVE ELEMENTS (OF PHLOEM) Sieve elements are specialized cells that function in the conduction of sugars. They are typically associated with parenchyma and often some sclerenchyma in a common tissue known as phloem (Gr. phloe, bark, after the location of secondary phloem in the inner bark).

Detailed explanation-2: -The structural elements of phloem include sieve tubes, companion cells, phloem parenchyma and secretory cells. The sieve tube is the conducting element of the phloem. It is formed from a vertical series of elongated cells, interconnected by perforations in their walls in areas known as sieve plates.

Detailed explanation-3: -The sieve tube members are living cells (which do not contain a nucleus) that are responsible for transporting carbohydrates throughout the plant. Sieve tube members are associated with companion cells, which are cells that combine with sieve tubes to create the sieve element-companion cell complex.

Detailed explanation-4: -Sieve tubes, which are columns of sieve tube cells having perforated sievelike areas in their lateral or end walls, provide the main channels in which food substances travel throughout a vascular plant.

Detailed explanation-5: -Phloem has sieve tubes, companion cells, bast fibers as its elements.