Identifying Vascular Tissue in Plant Sections

Steps:

• Examine cell orientation: elongated, parallel cells indicate a longitudinal section, not circular cross-sections of transverse.
• Identify tissue features: presence of sieve tube elements with sieve plates and companion cells points to phloem, not xylem's lignified vessels or tracheids.
• Rule out xylem: no thick-walled, hollow tubes or pits typical of xylem vessels.
• Confirm phloem specifics: longitudinal view reveals aligned, tapering sieve elements, distinguishing it from other options.

Why D is correct:

• Phloem in longitudinal section displays elongated sieve tube elements and perforated sieve plates, as defined in plant anatomy for transport tissue visualization.

Why the others are wrong:

• A: Transverse xylem shows circular vessel cross-sections and annular rings, not elongated cells.
• B: Transverse phloem reveals round sieve tube profiles without lengthwise alignment.
• C: Longitudinal xylem exhibits long tracheids or vessel elements with scalariform pits, lacking phloem's sieve plates.

Final answer: D