chapter 26

stimuli for plants could be

• light

• gravity

• co2 levels

• touch

• drought

• pathogen levels

a pathogen is

an infectious molecule

the process of responding to stimuli is called

the signal transduction pathway

signal transduction is the process of 

binding of a molecular signal that initiates a cellular response 

steps of a signal transduction pathway:

receptors, transduction pathway, cellular response

the cellular response in plants is usually

a change in gene expression

the transduction pathway is

a series of relay proteins who convert the original signal into one that affects the cellular machinery 

auxin is

a type of plant hormone

auxin causes

phototropism, gravitropism, and apical dominance

phototropism is

stem bending toward the light

phototropism happens because

auxin gathers on the shady side of the plant, hydrogen ions are pumped into the walls which causes them to weaken due to the change in pH and the wall will be rebuilt even bigger 

gravitropism is

roots grow down and shoots grow up

apical dominance is when

auxin inhibits the growth of the branches to focus on the plant growing up 

gibberellins are a plant hormone that causes

cell elongation

ctyokinins are a plant hormone that promotes

cell division and organ formation

cytokinins prevents

senescence or the aging of plants

cytokinins work and interact with

auxins

plants change color and die due to a

low cytokinin level

abscisic acid is a stress hormone that promotes 

dormancy 

ethylene is a gas hormone that causes fruits to

ripen

direct plant defense against predators

plant traits increase the resistance of host plants to affect the behavior of the attackers 

indirect plant defense against predators

plants attract natural enemies of the herbivores

movement to stimuli can be

internal and external

tropisms are

growth responses towards or away from external stimuli

positive is

towards the stimuli

negative is

away from the stimuli

phototrophism is positive in shoots and negative in

roots

plants can sense

the time of day and year

this sense is dependent on

phototrophin and phytochrome

phototrophins and phytochromes are

light receptor proteins in plants

phytochrome can detect and convert between

red wavelengths

pr and pfr are

forms of the phytochrome receptor

pr absorbs

red light and becomes pfr

pfr absorbs

far-red light in the evening and becomes pr

photomorphgenesis is when

shoots are exposed to red light causing pfr to accumulate making their leaves expand

etiolated is when

shoots increase in length but no photomorphgenesis because the plant is grown in the dark

competition: plants grown close together experience more far red light so 

the plants grow taller to compete for more sun 

photomorphgenesis and etiolated are types of

germination