plant responses to the environment Flashcards
what is an abiotic component
components of an ecosystem that are non-living
what is a biotic component
living components of a ecosystem
what are the three types of chemical defences
tannins- toxic to microorganisms and herbivores, make the leaf taste bad and prevent infiltration of pathogens
alkaloid- animal feeding deterrent make the plant taste bitter
pheromone- chemical released by one individuals which effect the behaviour or physiology of another
what is a tropism
directional growth response of a plant in response to a stimuli
what is a phototropism
directional growth response to light, usually grow towards light
what is a geotropism
directional growth response to gravitational pull
plant roots grow towards the direction of gravity
what is chemotropism
response attracted by chemicals
on a flower, pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertilisation occurs.
what is thigmotropism
response to gain support
directional growth response of shoots of climbing plants, such as ivy wind around other plants or solid structures to gain support.
what is a positive response
when a plant responds towards a stimulus.
For example, positive phototropism, plant grow towards the light.
what is a nastic response
not negative or positive, not a tropic response, as there is no direction
—– a non directional response to external stimuli
what is a cytokinin
promote cell division
overcome apical dominance- when central stem grows more than other branches
promote cell expansion
what is abscisic acid
inhibit seed germination and growth
causes stomatal closure when plant is stressed by low water availability
what is an auxin
promote cell elongation
inhibit growth of lateral buds and maintain apical dominance
inhibit leaf fall
what is a giberellin
promote seed germination and growth of stems
what is ethene
promote fruit ripening
what are the three types of movement of hormones in a plant
active transport
diffusion
mass flow
what coordinate plant responses to environmental stimuli
plant hormones- chemical messengers sent to target cells of plant
what happens when plant hormones reach the target cell of the plant.
they bind to receptors on the plasma membrane.
how does the plant make sure that hormones are acting upon the correct tissues
specific hormones have specific shapes, which only bind to complementary receptors.
ensures hormones only act on the right tissue
what is a negative tropic response
plant responds away from a stimuli
what is seed germination
a cell emerging from dormancy (temporary inactive period)
germination requires high energy, therefore has a high respiration rate
how do plant hormones move around the plant
active transport
diffusion
mass flow in phloem sap or xylem vessel
what is abiotic stress
non living environmental factor which can harm a plant
drought
poor oxygen supply
pollution
mineral deficiency
how do plants respond to herbivory and abiotic stress
produce bitter tannins
bitter alkaloid to deter animal feeding
release pheromones to trigger defensive responses in other organisms
