plant responses Flashcards
define stimulus
anything that causes a reaction in an organism or any of its parts
whats an animal stimulus
includes feeling pain/hunger, hearing a noise
whats a plant stimulus
light, gravity, temperatures
define response
the action pf a cell/organism as a result of a stimulus
give an example of an animal response
movement, production of enzymes and feeding
give an example of a plant response
growth, flowering
what is needed structurally for response
chemical/hormonal system (plants and animals), nerve and sense organ system, method of movement, immune system
what do plants depend on for their response
chemical co-ordination
define tropsim
a chenge in the growth of a plant in response to an external stimulus
define positive tropism
when the growth is towards the stimulus
define negative tropism
when the growth is away from the stimulus
what is the advantage of tropisms in a plant
they allow plants to obtain favourable growing contidtions
what is phototropism
change in growth in a plant in response to light
are stems positively phototropic
yes… allows the plant to get more sunlight
are roots positively phototropic or negatively phototropic
most are neg… e.g ivyy
what is geotropism
the change in growth of a plant in response to gravity
are roots positively geotrophic
yes, they grow downwards
are stems positvely geotrophic
no they are negatively geotrophic… grow against gravity
whats the benefit of roots growing towards gravity
can anchor the plant better, absorb water + minerals better
whats thigmotropism
the change in growth of a plant in response to touch
give an example of a plant that uses thigmotropism
climbing plants e.g ivy, vines, peas
what do positively thigmotropic plants grow to climb
tendrils which have positive thigmotropism
what’s hydrotropism
the change in growth of a plant in response to water
define chemotropism
the change in grwoth of a plant in response to chemicals
give an example of positive chemotropism
roots grow towards minerals… pollen tubes grow towards chemicals from the ovule
what might make a root negatively chemotropic
presence of harsh acids or heavy metals in soil e.g zinc/lead
what is a growth regulator
chemicals that control the growth of a plant
where are grwoth regulators mainly produced
meristem region
how are growth regulators transported
vascular tissues
give an example of a growth regulator which is a growth promoter?
auxins, e/g indoleactic acid (IAA)
what is the name given to a regulator that slows down plant growth
growth inhibitor e.g abscisic acid
where is IAA produced?
shoot tips, young leaves and seeds
give 3 functions of auxins
stimulate stem elongation and root growth, develop fruit, inhibit side branching in stems, cause phototropism and geotropism, cause cells to grow into different structures
what are some effects of auxins
tropism ( cell elongation and growth/bending), apical dominance, root growth (at low concentrations), fruit formation (IAA made in developing seeds… stimulates food to form in the fruit that surrounds the seed)
explain apical dominance
if the apical bud is intact, auxins produced in the tip will travel down the stem and it will inhibit lateral buds from developing. if apex is removed, side branches develop
explain the mechanism of a plant’s response to light
auxins loosen cell walls allowing them to expand. IAA is produced in the growth tips of the stem. if the stem is exposed to light from one side, IAA diffuses down the shaded side. concentration of IAA causes cells in shaded side to elongate more than bright side. as result of uneven elongation, stem bends towards light
what is the only growth regulator that is a gas
ethene gas
where is ethene gas used
to commercially ripen bananas
what is the role of ethene in a plant
causes fruit colour to form, fruit flavour to develop and fruit tissues to soften
name a growth inhibitor and state where it is produced
absisic acid… produced in leaves, stems and root caps
what is a stress regulator and give an example
absisic acid… causes plants to respond to harmful conditions
give an example as to how absisc acid helps regulate stress in plants
dry conditions it causes stomata to close in order to conserve water
name some comercially prepeared growth regulators
rooting powders(naphtyacetic acid), tissue culturing, ethene
list some structural adaptations in plants for protection
plants enclosed by a physical barrier e.g epidermis,bark,stingning hairs… guard cells close stomata when lack or water
list 2 chemical adaptations of plants for protection
excessive heat causes heat-shock proteins to form in order to protect enzymes… when a plant is infected it can produce stress proteins called photoalexins which attack micro-organism cell wall and stimulate production of plant cell walla to reduce micro-organism spread
