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D2.3.4—Changes in plant tissue

Plant tissue changes mass in sucrose or salt solutions, allowing isotonic concentration to be estimated from zero percent change in experiments.

Syllabus
First assessment 2025
Objective
D2.3.4
Level
SL

Exam analysis

Chance of appearing4%of analysed past papers
Latest appearanceNovember 2024
Most common paperPaper3
Typical marks1–2

Common command terms

  • Identify
  • Describe
  • Explain
  • Suggest
  • Evaluate
  • Outline

Scoring notes

Common mistake
Using raw mass change instead of percentage change when initial masses differ.

Recent exam appearances

November 2024Paper3 ["SL"] · TZ11(c)[ 1 ]D2.3.4—Changes in plant tissue
November 2024Paper3 ["SL"] · TZ11(b)[ 2 ]D2.3.4—Changes in plant tissue
May 2024Paper3 ["SL"] · TZ21(c)[ 2 ]D2.3.4—Changes in plant tissue
November 2023Paper1 ["SL"] · TZ23[ 1 ]D2.3.4—Changes in plant tissue
November 2019Paper3 ["SL"] · TZ01(d)[ 2 ]D2.3.4—Changes in plant tissue

Coverage 2016–2024 · Updated 16 Jul 2026

A Fair Plant-Tissue Test Is Built before It Is Measured

1

A plant-tissue osmosis investigation asks how bathing-solution concentration changes tissue mass or length while other influential variables are controlled.

Prepare: make a range of accurately measured sucrose concentrations; cut tissue from the same plant source to equal starting dimensions; record each sample's initial mass or length.

2

Expose: immerse replicate samples at every concentration for the same time and at the same temperature.

3

Measure: remove each sample, blot it with the same pressure and duration, then record final mass or length.

Control or design choice Why it matters
same tissue source and starting dimensions limits biological and surface-area variation
same solution volume, time and temperature keeps exposure and movement rate comparable
uniform blotting prevents surface liquid from being counted as tissue mass
replicates at every concentration reveals variation and supports a reliable mean

Percentage Change Makes Different Samples Comparable

percentage change = ((final value − initial value) ÷ initial value) × 100

A potato cylinder changes from 4.00 g to 4.36 g.

change = 4.36 − 4.00 = 0.36 g

percentage change = (0.36 ÷ 4.00) × 100 = +9.0%

Result Interpretation
positive percentage tissue gained water overall
zero percentage no detected net change
negative percentage tissue lost water overall

Plot mean percentage change on the y-axis against sucrose concentration on the x-axis. Percentage change normalizes samples that did not begin with exactly the same mass or length.

The Zero-Change Intercept Estimates the Isotonic Concentration

The sucrose concentration where the fitted relationship crosses 0% change estimates the concentration isotonic with the tissue: water still moves, but there is no net osmosis.

Judge the estimate using the data, not only the drawn line:

  • use replicate means rather than one sample
  • inspect spread or error bars
  • interpolate only within the measured concentration range
  • report appropriate precision rather than extra decimal places

A zero mean can hide variation among samples. It estimates the tissue's isotonic point under these conditions; it is not proof that every cell had identical concentration.

Mean percentage change in plant-tissue mass falls as sucrose concentration increases and crosses zero at the estimated isotonic concentration.

Osmosis Links Measurements, Cell Structure and Safe Fluid Choice

solution concentration → net water movement → change in tissue mass, length, cell volume or pressure → observable cell or tissue outcome

Evidence What it supports
positive plant-tissue percentage change bathing solution was hypotonic to the tissue
zero-change graph intercept estimated isotonic concentration
animal-cell lysis or crenation large water gain or loss without wall resistance
plant-cell turgor or plasmolysis water gain or loss modified by wall mechanics
stable cells in a medical bath solution is effectively isotonic with the tissue

First determine where water moves; then use cell structure to predict the consequence. The same osmotic rule explains a graph intercept, a red blood cell, a plant cell and the choice of a medical fluid.

Changes in plant tissue

[ 2 ]

Student osmosis experiments often involve putting plant tissue such as potato cylinders in several salt solutions of different concentrations and measuring the mass before and after immersion. Outline how data collected from such an experiment could be used to estimate the osmolarity of the plant tissues.

Concept essentials

  • Percentage change in mass shows relative water gain or loss.
  • The isotonic concentration is where mass change is zero.
  • Hypotonic solutions cause plant tissue to gain water.
  • Controlled variables make osmolarity estimates more reliable.