Plant Response Flashcards
Response
A reaction in an organism as a result of a stimulus
Structures necessary for a plant response
Hormonal system - plant + animal
Nervous system - animal
Immune system
Hormone
A chemical produced in one part of an organism and transported to another part where it has its effect
External stimuli
Light intensity Day length Gravity Temperature Water
Internal stimuli
Growth regulators - chemicals
Tropism
Growth tendency of a plant in response to an external stimulus
Types of Tropism
Phototropism Geotropism Hydrotropism Thigmotropism Chemotropism
Phototropism
Growth tendency of a plant in response to light
Shoots - positive
Roots - mainly negative
Geotropism
Growth tendency of a plant in response to gravity
Roots - positive
Shoots - negative
Thigmotropism
Growth tendency of a plant in response to touch
Climbing plants
Hydrotropism
Growth tendency of a plant in response to water
Roots and pollen tubes - positive
Chemotropism
Growth tendency of a plant in response to chemicals
Pollen tubes - positive to ovule
Growth regulators
A chemical which controls the growth of a plant
Produced at the tip of the meristem
Transport to the zone of elongation in phloem and xylem
Promotes root growth at high concentration
Active in small amounts
Growth promoter
Auxins - IAA
Growth inhibitor
Abcistic acid or ethene
Stimulation
Any change in the environment which causes a response in an organism
Mechanisms of Phototropism
Causes more auxin to diffuse to shaded side
More growth on shaded side
Plant bends towards light
Plant shoot and leaves in a favorable position for maximum light and maximum photosynthesis
Mechanisms of Geotropism
IAA causes root growth at low concentration
Gravity causes more IAA to be collected at lower side of the root
Root grows towards gravity
Roots are in a favorable position to absorb water and minera
Commercial growth regulators
NAA AND IBA: commercial roofing powders to stimulate root growth
Gibberellins: increase the size of fruit
Ethene: ripening agent for food
Anatomical plant adaptations for protection
Bark to protect trees Thorns Spines Stinging hairs /needles Waxy cuticles on leaves
Chemical plant adaptations for protection
Corn lily is poisonous
Poison Ivy produces a chemical to protect the plant from herbivores
Where is Auxin produced
Meristematic tissue
Inhibitory function of auxin
Apical dominance
