B3.2.9—Stem tissue distribution
Dicot stems arrange vascular bundles in a ring, with xylem, phloem, cambium and supporting tissues positioned for transport and support.
- Syllabus
- First assessment 2025
- Objective
- B3.2.9
- Level
- HL
Exam analysis
Chance of appearing6%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1
Common command terms
- Identify
- Label
- Describe
Scoring notes
- Common mistake
- Confusing xylem and phloem positions within a dicot stem vascular bundle.
Recent exam appearances
November 2025Paper1A ["HL"] · TZ124[ 1 ]B3.2.9—Stem tissue distribution
November 2021Paper1 ["HL"] · TZ032[ 1 ]B3.2.9—Stem tissue distribution
May 2021Paper1 ["HL"] · TZ233[ 1 ]B3.2.9—Stem tissue distribution
November 2019Paper1 ["HL"] · TZ033[ 1 ]B3.2.9—Stem tissue distribution
November 2018Paper3 ["HL"] · TZ02(c)[ 2 ]B3.2.9—Stem tissue distribution
Practice this objective
Coverage 2014–2025 · Updated 15 Jul 2026
Stem Tissues Place Transport in Separate Paths
Stem tissues arrange vascular bundles so xylem and phloem connect roots, leaves and growing regions while support tissues maintain the stem.
Xylem position and lignification support water flow and mechanical strength; phloem provides living conduits for assimilate movement. Arrangement changes with organ and growth pattern.
Identify tissue by wall structure and cargo before assigning its direction through the stem.
A vascular bundle can carry water upward in xylem while phloem distributes sucrose from a source leaf to a growing sink.
A stem cross-section is not interpreted by labels alone: identify tissue by wall structure, contents and direction of transported material.
Stem tissue distribution
Assessment in practice
1 marksHow it is assessed
This objective is assessed through structured response, commonly using Identify / Label / Describe.
Command terms
Identify / Label / Describe
What earns marks
Build the answer around this relationship: Dicot stem vascular bundles are arranged in a ring.
Watch for
Confusing xylem and phloem positions within a dicot stem vascular bundle.
Representative question
Question 1
Describe the distribution of vascular tissues in the stem of dicotyledonous plants.
Link Transport Structure To Function
Animal and plant transport answers should link structure to function. In animals, capillaries exchange, arteries maintain high-pressure flow, veins return low-pressure blood, pulse measures arterial pressure waves, and coronary occlusion blocks oxygen delivery to heart muscle. In plants, xylem transports water by transpiration tension and cohesion, while stem and root tissue plans show where xylem and phloem are arranged.
- Blood vessel answers need structure plus pressure or exchange function.
- Xylem answers need transpiration pull, cohesion, adhesion, lignin, pits, and hollow vessels when relevant.
- Plant diagrams should identify tissue distribution: stem vascular bundles in a ring, root xylem cross with phloem between arms.
Concept essentials
- Dicot stem vascular bundles are arranged in a ring.
- Xylem is usually nearer the centre of each bundle, with phloem toward the outside.
- Phloem is the tissue responsible for sucrose translocation.
- Plan diagrams emphasise tissue positions rather than individual cells.