5.5 Plant and animal responses Flashcards
what are the different types of stimuli in plants
-tannins
-alkaloids
-pheromones
what are tannins
-toxic to microorganisms + large herbivores
-in leaves found in upper epidermis, making leaf taste bad
-in roots prevent infiltration by pathogenic microorganisms
what are alkaloids
-derived from amino acids
-feeding deterrent to animals, bitter
-in growing tips and flowers and peripheral cell layers of stems and roots
what are pheromones
-chemicals which are released by one individual and can affect the behaviour oh physiology of another
what are the different types of response in plants
-phototropism
-geotropism
-chemotropism
-thigmotrophism
what are tropisms
directional growth responses of plants
describe a phototropism
shoots grow towards light which enables them to photosynthesise
describe a geotropism
roots grow towards the pull of gravity which anchors them in the soil and helps them to take up water which is needed for support as a raw material and to help cool the plant
describe a chemotropism
on a flower, pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertilisation can take place
describe thigmotropism
shoots of climbing plants wind around other plants or solid structure to gain support
what is a positive tropic response
when a plant responds towards a stimulus
what is a negative tropic response
when a plant responds away from a stimulus
what are nastic responses
non-directional responses to external stimuli
describe an example of thigmonasty
Mimosa pudica responds to touch with a sudden folding of the leaves
what effects do cytokinins have
-promote cell division
-delay leaf senescence
-overcome apical dominance
-promote cell expansion
what effects does abscisic acid have
-inhibits seed germination and growth
-causes stomatal closure when the plant is stressed by low water availability
what effects do auxins have
-promote cell elongation
-inhibit growth of side shoots
-inhibit leaf abscission (leaf fall)
what effects do gibberellins have
-promote seed germination and growth of stems
what effects does ethene have
-promotes fruit ripening
what hormones do plants contain
-cytokinins
-abscisic acid
-auxins
-gibberellins
-ethene
how do hormones move around the plant
-active transport
-diffusion
-mass flow in the phloem sap or in xylem vessels
