Plant responses summary (A-Level 2nd Year)

Plant responses: Roles of Plant Hormones + their
Commercial uses


 Survive + reproduce so can pass on alleles to their offspring



Plant Responses
 Respond to abiotic (non-living = light, water…) + biotic (living =
bacterial/fungal pathogens, herbivores…) stimuli (changes in environment)




Chemical Responses to Herbivory
Reduces effects of herbivores on them…


 Tannins – Toxic to herbivores + microorganisms + taste bad


 Alkaloids – Toxic to insects + taste bitter


 Pheromones- released into air (attract insects to flowers so they can pollinate
them) vulnerable to herbivory (act as alarm to warn neighbouring plants); can
be stimulus to other plants; these plants then respond by producing (own
defence) tannins etc…


Touch Response to Herbivory
 Mimosa Pudica – Leaf folding; causes insects to drop off; causes
herbivores to be alarmed.



Plant Responses – Tropisms
 Tropisms – directional response to abiotic stimulus (direction of
stimulus/away from direction of stimulus)
 Positive Tropism – Moves towards stimulus
 Negative Tropism – Moves away stimulus