This document provides a cheat sheet on key plant function concepts for AP Biology including plant hormones, reproduction, and defense. It lists the five major plant hormones- auxins, cytokinins, gibberellins, abscisic acid, and ethylene- and their effects on processes like cell growth and dormancy. Plant reproduction structures like flowers and their male and female parts are defined. Finally, it outlines natural physical and chemical barriers to pathogens as well as inducible defense responses like systemic acquired resistance.

1. AP Biology - Core Concept Cheat Sheet
18: Plant Function
Key Concepts
Plant Hormones
Five major types
• Apical dominance: Apical dominance is the inhibition of
lateral buds by auxin from the apical bud; the effect is
therefore the apical bud becomes active.
• Cotyledon: The seed leave(s) that can be used to classify
plants.
• Endosperm: Generated from fertiliztion of the central
cells. All endosperm cells contain 3N nucleus and supply
nutrients for embryo development and/or seed
germination.
• Hypersensitive response: When a plant is infected by a
pathogen, it often triggers a hypersensitive response to kill
the infected cells; therefore, the pathogen would not
spread.
• Macronutrients: 9 elements required in large quantity
that plants absorb from air and soil to support their growth.
These include C,H, O, N, P, K, Ca, Mg and S.
• Micronutrients: 7 elements required in small quantities
that plants absorb from air and soil, inculding boron,
copper, iron, chloride, manganese, molybdenum, and zinc.
• Systemin: The signal molecule a plant synthsizes in
response to wounding
• Transpiration: Evaporation via the stomata on the lower
surface of leaves that pulls up water/minerals from roots.
This force makes water to go upwards from root to leaves.
• Auxins:
o Stimulate cell elongation
o Stimulate cell division
• Effects on plants:
o Apical Dominance
o Phototropism
o Gravitropism
o Inhibit Leaf Abscission
o Leaf Formation
o Embryonic Development
o Fruit Development
o Root Initiation
• Cytokinins
o Stimulate cell division
o Promote growth of lateral
buds
• Gibberellins
o Promote stem elongation
o Breaks seed dormancy
• Abscisic Acid
o Bud dormancy
o Seed maturation and
dormancy
o Abscission of leaves and fruits
o Closing of stomata
Plant Reproduction
Stigma
sepal
Ovary
• Ethylene
o Promote fruit ripening
o Stimulates senescence and
abscission in leaves and
fruits
Anther
Filament
Pedal
Plant Defense
Structure of a flower
• Female organs -- carpel
o Stigma on top
o Ovary (containing megaspores)
Natrual Physical barrier:
o
Cuticle: a layer of wax on surface of leaves
o
Trichomes: extension of plant cells
o
Spines (modified leaves)
o
Bark
• Male organs -- stemina
o Filament
o Anther (containg microspores)
Natural Chemical barier
o Isoprene
o Phenolic compounds
o Alkaloids
• Leave-like Structure
o Sepal
o Pedal
• Double pollination
o Pollen contains 2 sperms, one pollinate one egg cell -->
embryo
o Another sperm pollinate central cell --> endosperm
• Seed
o Seed coat
o Cotyledon(s)
o Endosperms
CH2=CH2
Inducible Response:
o Response to wound --> systemin
o Response to pathogen --> SAR, systemic acquired
resistance
o Gene-for-gene theory: To every pathogen avirulence
(avr) gene, there is a coresponding R gene (resistance
gene) in plant to trigger HR
How to Use This Cheat Sheet: These are the keys related this topic. Try to read through it carefully twice then recite it out on a
blank sheet of paper. Review it again before the exams.
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