Sieve Element Structure in Phloem

Steps:

• Recall sieve elements are elongated phloem cells with porous sieve plates for sap flow.
• Identify key visible features in a longitudinal electron micrograph: thick cell wall, sieve plate (end wall with pores), and cytoplasm.
• Evaluate labels: must include wall, cytoplasm, and sieve plate; avoid non-essential organelles like mitochondria, which are sparse.
• Match options to standard diagram: C includes all essentials without extras.

Why C is correct:

• Sieve elements feature a cell wall perforated by sieve plates and contain cytoplasm for mass flow of nutrients, per phloem transport definitions.

Why the others are wrong:

• A omits cytoplasm, essential for visualizing sap movement.
• B labels mitochondrion, not a prominent or defining sieve element feature.
• D adds mitochondrion, incorrect as sieve elements have reduced organelles.

Final answer: C