how plants respond to the environment
to cope w changing conditions + avoid abiotic stress
to maximise photosynthesis by obtaining more light, more water and more minerals
to avoid herbivory and grazing
to ensure germination of its seeds in suitable conditions
some have diff effects on diff tissues
some amplify each others effects - synergy
some cancel eachother out - antagonistic
some are commercially important and can be used to produce plants as ornaments or food
hormone | effects |
auxins | associated w cell enlargement and differentiation. prevent leaf fall. maintains apical dominance. tropisms. stimulate ethene release |
gibberellins | associated w cell enlargement + differentiation. germination. pollen tube growth |
cytokinins | associated w cell division |
abscisic acid | associated w dormancy + stomatal closure. cold protective response |
ethene | associated w ageing. causes fruit ripening, promotes leaf fall (abscission) |
physical
thorns, barbs, spikes, inedible tissues, hairy leaves, stings
chemical
tannins, alkaloids, terpenoid, pheromones
types of phenols
bitter taste deterring herbivory
toxic to insects
very bitter N compound.
act as drugs affecting animals metabolism e.g. caffeine, nicotine
can be toxic to insects and fungi
produced by plants as essential oils
toxic to insects and fungi
can be used as insect repellent e.g. lemongrass (citronella)
chemical made by an organism which affects social behavior of other members of same species
maple trees, water stress, cabbages, apple trees, wheat seedlings
pheromone | effect |
maple tree | Pheromone causes CALLOSE (polysaccharide/physical barrier) to form when the tree is under attack from insects. Causes response in adjacent branches and on adjacent trees. |
apple tree | When under attack from spider mites, pheromone released and attracts predatory mites to destroy apple tree pest. |
cabbages | attacked by caterpillars of cabbage white butterfly. Pheromone released that attracts parasitic wasp. Wasp lays eggs in caterpillar which then gets eaten alive. diff pheromones released by cabbage if under attack by different pest e.g. green fly and a different parasitic wasp is attracted. |
tropisms are tropic movements (directional responses) seen in plants, in response to variety of possible stimuli
chemotropism: directional response to chemicals
phototropism: directional response to light stimuli
thermotropism: directional response to temperature
hydrotropism: directional response to water
thigmotropism: directional response to touch
movement toward environmental stimulus is called positive tropism, movement away from stimulus is called negative tropism
shoot tips of plant that grow toward light source are positively phototropic
nasties are nastic movements (non-directional responses) which plants have in response to stimuli
chemonasty
photonasty
thermonasty
hydronasty
thigmonasty
to cope w changing conditions + avoid abiotic stress
to maximise photosynthesis by obtaining more light, more water and more minerals
to avoid herbivory and grazing
to ensure germination of its seeds in suitable conditions
some have diff effects on diff tissues
some amplify each others effects - synergy
some cancel eachother out - antagonistic
some are commercially important and can be used to produce plants as ornaments or food
hormone | effects |
auxins | associated w cell enlargement and differentiation. prevent leaf fall. maintains apical dominance. tropisms. stimulate ethene release |
gibberellins | associated w cell enlargement + differentiation. germination. pollen tube growth |
cytokinins | associated w cell division |
abscisic acid | associated w dormancy + stomatal closure. cold protective response |
ethene | associated w ageing. causes fruit ripening, promotes leaf fall (abscission) |
physical
thorns, barbs, spikes, inedible tissues, hairy leaves, stings
chemical
tannins, alkaloids, terpenoid, pheromones
types of phenols
bitter taste deterring herbivory
toxic to insects
very bitter N compound.
act as drugs affecting animals metabolism e.g. caffeine, nicotine
can be toxic to insects and fungi
produced by plants as essential oils
toxic to insects and fungi
can be used as insect repellent e.g. lemongrass (citronella)
chemical made by an organism which affects social behavior of other members of same species
maple trees, water stress, cabbages, apple trees, wheat seedlings
pheromone | effect |
maple tree | Pheromone causes CALLOSE (polysaccharide/physical barrier) to form when the tree is under attack from insects. Causes response in adjacent branches and on adjacent trees. |
apple tree | When under attack from spider mites, pheromone released and attracts predatory mites to destroy apple tree pest. |
cabbages | attacked by caterpillars of cabbage white butterfly. Pheromone released that attracts parasitic wasp. Wasp lays eggs in caterpillar which then gets eaten alive. diff pheromones released by cabbage if under attack by different pest e.g. green fly and a different parasitic wasp is attracted. |
tropisms are tropic movements (directional responses) seen in plants, in response to variety of possible stimuli
chemotropism: directional response to chemicals
phototropism: directional response to light stimuli
thermotropism: directional response to temperature
hydrotropism: directional response to water
thigmotropism: directional response to touch
movement toward environmental stimulus is called positive tropism, movement away from stimulus is called negative tropism
shoot tips of plant that grow toward light source are positively phototropic
nasties are nastic movements (non-directional responses) which plants have in response to stimuli
chemonasty
photonasty
thermonasty
hydronasty
thigmonasty
