Plant Responses Chp32 Flashcards
What is a stimulus
anything that causes a reaction in an organism or in any of its parts
What is a response
the activity of a cell or organism as a result of a stimulus
What are the structures needed for response
a chemical/hormonal system, a nerve/sense organ system, a method of movement, a defence/immune system
What are the external factors effecting plant growth
light, day length, gravity, temperature
What is a tropism
a change in the growth of a plant in response to an external stimulus
What is a positive tropism
when the growth is towards the stimulus
What is a negative tropism
when the growth is away from the stimulus
What is phototropism
the change in growth of a plant in response to light (stem)
What is geotropism
the change in growth of a plant in response to gravity (root)
What is thigmotropism
a change in growth of a plant in response to touch
What is hydrotropism
a change in growth of a plant in response to water
What is chemotropism
a change in plant growth in response to chemicals
What is a growth regulator
a chemical that controls the growth of a plant
What is a growth promoter
a chemical that causes increased growth in plants
What is an example of a growth regulator
Auxins/IAA
Where are auxins produced
meristematic tissue in the tips of shoots
What are the functions of auxins
stimulate stem elongation, developing fruit, apical dominance, causing phototropism
What are the effects of auxins
causes cell elongation/growth on opposite side of the sun bending the plant toward the light
Describe the role of IAA in phototropism
IAA diffuses down the shaded side of the plant, this causes the cells to elongate more, as a result the stem bends towards the light
What are growth inhibitors
a chemical that causes a reduction in growth of plants
How are growth regulators used in horticulture
ethene is used to ripen fruits and rooting powders are used to stimulate rapid root formation on stem cuttings
2 ways plants are anatomically adapted for protection
epidermis or bark prevents the entry of pathogens and reduce the loss of water, guard cells shrivel due to a lack of water reducing further water loss
2 ways plants are chemically adapted for protection
heat-shock proteins surround enzymes to protect them from being denatured in high heat, plant produces phytoalexins (stress proteins) damaging micro-organisms by attacking cell walls
