DENDROLOGY

Detailed explanation-1: -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-2: -Phloem, the vascular tissue responsible for transporting organic nutrients around the plant body, carries dissolved sugars from the leaves (their site of production) or storage sites to other parts of the plant that require nutrients.

Detailed explanation-3: -Sieve elements are specialized cells that are important for the function of phloem, which is a highly organized tissue that transports organic compounds made during photosynthesis. Sieve elements are the major conducting cells in phloem.