Read Xylem and Phloem by Position and Function
Xylem and phloem combine transport with structural roles and have distinctive cell types.
Living-system questions are solved by matching a structure or organism to its function, process and stated condition.
Use xylem position
Protoxylem forms first. It is endarch in stems (toward the centre) and exarch in roots (toward the periphery); metaxylem forms later.
Read phloem anatomy
Sieve plates are perforated end walls between sieve-tube members. Sieve elements are living but enucleate; companion cells are nucleated and generally absent from gymnosperms, which instead have albuminous cells. Phloem fibres are common in secondary phloem.
Separate functions
Xylem conducts water and minerals and also provides mechanical strength. These are both true functions, but conduction alone is not the explanation for mechanical support.
OlympIQ exam lens
- ✓Protoxylem first: endarch stem, exarch root.
- ✓Metaxylem later.
- ✓Sieve plates are perforated end walls.
- ✓Xylem conducts and supports.
Do not reverse protoxylem and metaxylem or endarch and exarch.
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