Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

8.3Transport in Plants

Transpiration — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 18 parts Lesson 6 of 9 1 quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read
Lesson summary

8.3 Transpiration — IGCSE BIOLOGY notes: Define transpiration, explain the transpiration stream and the effect of temperature, wind and humidity, and describe wilting.Transpiration = the loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophy…

  • Water supply
  • Photosynthesis
  • Evaporation site
  • Surface area
  • Direction — Movement in the xylem is in one direction only, from roots to leaves
  • Minerals — Transports mineral ions

Part 1 of 8Transpiration

Transpiration
Transpiration the loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.
Water supply
  • Water travels up the xylem from the roots to replace the water lost.
Direction
  • Movement in the xylem is in one direction only, from roots to leaves.

Part 2 of 8Functions of transpiration

Functions of transpiration
Minerals
  • Transports mineral ions.
Support
  • Provides water to keep cells turgid.
Photosynthesis
  • Provides water to leaf cells.
Cooling
  • Heat energy is used to change liquid water into vapour, which cools the plant.

Part 3 of 8Water vapour loss (Supplement)

Evaporation site
  • Water evaporates from the surfaces of the spongy mesophyll cells.
Surface area
  • The interconnecting air spaces and the stomata create a large surface area.
Result
  • Evaporation is rapid when the stomata are open.

Part 4 of 8Transpiration stream (Supplement)

Cohesion
  • Water molecules attract each other and form a continuous column up the plant.
Pull
  • Water loss from the leaves produces tension on the water in the xylem.
Rate
  • If transpiration increases, water is pulled up the xylem faster.

Part 5 of 8Investigating temperature and wind speed

1
Dry the leaves and cut the shoot under water.
2
Place the shoot in the tube and make the apparatus airtight with Vaseline.
3
Let one air bubble form in the capillary tube.
4
Set up the environmental factor and let the plant acclimatise for 5 minutes.
5
Record the starting position of the bubble and leave for a set time.
6
Record the end position; the further it moves, the faster the water uptake.
7
Change only temperature or wind speed, reset the bubble and repeat.

Part 6 of 8Effects of environmental factors (Supplement)

FactorConditionRateReason
Wind speedHighFasterAir movement removes vapour and keeps a steep gradient out of the stomata
HumidityHighSlowerSmaller concentration gradient between leaf air spaces and the air
TemperatureHighFasterMore kinetic energy increases evaporation and diffusion

Part 7 of 8Wilting (Supplement)

Cause
  • More water evaporates from the leaves than the roots can take up from the soil.
Effect
  • Cells are no longer full of water, so the cell walls cannot support the plant and it collapses.

Part 8 of 8More from the specification

Phloem
  • Tissue carrying sucrose and amino acids.
Vessel
  • A long tube formed from dead xylem cells.
Translocation
  • Movement of sucrose and amino acids in phloem from sources to sinks.
Sucrose
  • The sugar mainly transported in phloem.
Tissue
  • A group of cells of similar structure that perform the same function.
Xylem vessel
  • A tube of dead lignified cells carrying water upwards.

Key terms

TermMeaning
TranspirationLoss of water vapour from leaves by evaporation and diffusion through stomata.
Transpiration streamContinuous movement of water up the xylem from roots to leaves.
CohesionAttraction between water molecules.
StomataPores in the leaf through which water vapour leaves.
WiltingCollapse of a plant when water loss exceeds water uptake.
PotometerApparatus measuring the rate of water uptake of a shoot.

Avoid these mistakes

1
Saying transpiration is only evaporation — it is evaporation followed by diffusion through the stomata.
2
Saying high humidity speeds transpiration — it slows it.
3
Not controlling other factors in the investigation — change only one factor.
4
Saying a potometer measures transpiration exactly — it measures water uptake as an estimate.

Last updated: