IMO Practice Test — Anatomy of Flowering Plants
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
Why can a dicot stem grow thicker over years while a typical monocot palm cannot?
Dicot stems have a vascular cambium (open bundles); monocots lack it (closed bundles)
Monocots have more water
Dicots have no xylem
Palms are not plants
Explanation: Open dicot bundles have cambium enabling secondary growth; closed monocot bundles do not.
Question 2 of 6
The trunk of an old tree is mostly secondary xylem because the cambium:
Adds far more xylem (inward) than phloem (outward)
Adds only phloem
Stops dividing early
Makes only cork
Explanation: The vascular cambium produces much more secondary xylem than phloem, so wood dominates the trunk.
Question 3 of 6
Counting 30 annual rings in a tree trunk suggests the tree is about:
30 years old
60 years old
15 years old
300 years old
Explanation: Each annual ring represents one year's growth, so 30 rings ≈ 30 years.
Question 4 of 6
Collenchyma is well suited to support young, growing stems because it is:
Thickened yet living and flexible, so it bends without breaking
Dead and rigid
Unable to support anything
Made of cork
Explanation: Collenchyma's uneven living thickening gives flexible support that allows bending growth.
Question 5 of 6
A cross-section shows vascular bundles scattered throughout the ground tissue with no cambium. The organ is a:
Monocot stem
Dicot stem
Dicot root
Dorsiventral leaf
Explanation: Scattered, closed bundles with no cambium are the hallmark of a monocot stem.
Question 6 of 6
Bulliform cells in a monocot (e.g. grass) leaf help the plant by:
Rolling/folding the leaf to reduce water loss in dry conditions
Conducting water
Producing flowers
Storing chlorophyll
Explanation: When water is scarce, bulliform cells lose turgor and the leaf rolls/folds, cutting transpiration.