Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

AP Biology - Plants and Human Body Systems

AP Biology Chapter 14 — Plants: Structure, Transport and Hormones — AP BIOLOGY Revision Notes & Topical Questions

5 min read 8 parts Lesson 1 of 15 1 quiz

📚 AP BIOLOGY 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

AP Biology Chapter 14 — Plants: Structure, Transport and Hormones — AP BIOLOGY notes: Describe plant cell types, water transport and stomata, root growth, plant hormones, tropisms and photoperiodism.Cell typeAlive at maturityFunctionParenchymaYesThin-walled; photosynthesis, stora…

  • Cohesion-tension
  • Zone of cell division (apical meristem)
  • Zone of elongation
  • Zone of maturation (differentiation)
  • Phototropism
  • Gravitropism

Section 1 of 8Plant tissues and cell types

Cell typeAlive at maturityFunction
ParenchymaYesThin-walled; photosynthesis, storage and repair
CollenchymaYesUnevenly thickened primary walls; flexible support of young stems and petioles
Sclerenchyma (fibres, sclereids)Usually noThick lignified secondary walls; rigid support
Tracheids (xylem)NoLong, thin cells; water passes through pits, more slowly
Vessel elements (xylem)NoWider, with perforated end walls joined end to end; more efficient water conduction
Sieve-tube members (phloem)YesCarry sugars (translocation)
Companion cells (phloem)YesKeep sieve-tube members alive
Guard cellsYesPairs of cells that open and close each stoma

Section 2 of 8Water transport

1Pathway
  • Pathway water moves from root through xylem to leaf and out to the air.
2Cohesion-tension
  • Cohesion-tension evaporation from leaves (transpiration) pulls the water column up.
3
Transpiration is fastest when it is hot, dry, windy and bright.
  • The water-vapour gradient is steep and the stomata are open.

Section 3 of 8Stomata

Opening
  • Opening guard cells take up K+, water follows by osmosis, the cells swell and bow apart, and the stoma opens.
Closing
  • Closing loss of K+ and water makes the guard cells flaccid and the stoma closes.
Stomata are usually open in light because CO2 is needed, and closed at night.
They also close in drought, under the influence of abscisic acid, and when very hot and dry.
CAM plants reverse this pattern and open their stomata at night.

Section 4 of 8Root growth

1Root cap
  • Root cap protects the tip and senses gravity.
2Zone of cell division (apical meristem)
  • Zone of cell division (apical meristem) makes new cells by mitosis.
3Zone of elongation
  • Zone of elongation cells lengthen, which pushes the root forward.
4Zone of maturation (differentiation)
  • Zone of maturation (differentiation) cells specialise and root hairs form.

Section 5 of 8Plant hormones

HormoneMain effects
Auxin (IAA)Cell elongation; phototropism and gravitropism; apical dominance
GibberellinsStem elongation; break seed dormancy (germination); bud growth, flowering and fruit growth
CytokininsCell division; delay senescence (ageing)
Ethylene (gas)Fruit ripening; leaf abscission in autumn; senescence
Abscisic acid (ABA)Seed dormancy; stomatal closure in drought

Section 6 of 8Tropisms and photoperiodism

Phototropism
Phototropism growth toward light.
  • Auxin moves to the shaded side, those cells elongate more, and the stem bends toward the light.
Gravitropism
  • Gravitropism roots grow down and shoots grow up.
Thigmotropism
  • Thigmotropism growth in response to touch, such as a vine coiling round a support.
Photoperiodism
  • Photoperiodism flowering controlled by night length, detected by phytochrome.

Section 7 of 8Key terms

TermMeaning
TranspirationEvaporation of water from leaves.
Cohesion-tensionPulling of the water column up the xylem by transpiration.
AuxinHormone causing cell elongation and tropisms.
Abscisic acidHormone causing seed dormancy and stomatal closure.
PhototropismGrowth toward light.
PhotoperiodismResponse, such as flowering, to night or day length.

Section 8 of 8Exam technique

1
Saying xylem carries sugars — phloem carries them (translocation)
2
Thinking auxin moves to the lit side — it moves to the shaded side
3
Saying sclerenchyma is alive at maturity — it is usually dead
4
Believing stomata close in light — they usually open in light and close at night or in drought

Last updated: