Plant Responses Flashcards
biotic
living e.g. competition
abiotic
non-living e.g. pH
tannins
toxic to microorganisms/herbivores found in leaves which make them taste bad and prevent infiltration by pathogens in roots
alkaloids
located in growing tips/flowers/stems/roots, taste bitter so feeding deterrent to animals
pheromones
chemicals released by one individual and affect behaviour/physiology of another
tropic (directional) response
if a plant responds towards or away from a stimulus
nastic (non-directional) reponse
external stimuli e.g. Mimosa pudica responds to touch by sudden folding of leaves
phototropism
shoot grows towards light for photosynthesis
geotropism
roots grow towards the pull of gravity
chemotropism
on a flower, pollen tubes grow down the style attracted by chemicals towards the ovary where fertilisation happens
thigmotropism (touch)
shoots of climbing plants wind around other structures to gain support
how do hormones work in plants
transported by active transport, diffusion, mass flow and bind to receptors on target cell membranes with complementary binding sites
auxins
promote cell elongation, inhibit growth of side-shoots, leaf abscission
gibberellins
promote seed germination and growth of stems
cytokinins
promote cell division, delay leaf senescence, overcome apical dominance, promote cell expansion
abscisic acid
inhibits seed germination/growth, causes stomatal closure when water stress
ethene
promotes fruit ripening
effects brought about by application of gibberellic acid
stem elongation in dwarf plants, bolting in long days, fruit development/growth, seed germination
how to test phototropic responses
expose shoot to light
how to test geotropic responses
constantly spin by a clinostat for even gravity, for experimental it is not switched on
why can only meristem cells divide
the cell wall limits its ability to divide and expand so only immature cells can
tropism
a directional growth response in which the direction of the response is determined by the direction of the stimulus
apical dominance
inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of a shoot
coleoptile
a sheath and enclosed leaf on the root tip of an oat/barley/wheat seedling
