Plant Responses

Question 1

stimulus

Answer 1

a change in the environment that causes response in an organism

Question 2

plant growth regulators

Answer 2

chemicals (hormones) that control plant growth

Question 3

auxins

Answer 3

hormones that regulate growth in plants

Question 4

tropism

Answer 4

a response to a stimulus

Question 5

phototropism

Answer 5

growth of a plant in response to light

Question 6

geotropism

Answer 6

the growth response of a plant to gravity

Question 7

thigmatropism

Answer 7

the growth response of a plant to touch

Question 8

hydrotropism

Answer 8

the growth response of a plant’s roots to water

Question 9

chemotropism

Answer 9

the growth response of a plant to chemicals

Question 10

adverse external environment

Answer 10

surroundings which are harmful to organisms

Question 11

stock solution

Answer 11

solution of known concentration

Question 12

serial dilution

Answer 12

a series of dilutions of stock solution of known concentration

Question 13

external factors that regulate growth

Answer 13

light intensity: required for energy for photosynthesis
day length: causing plants to flower
gravity: shoots grow up, roots grow down
temperature: affects enzyme activity

Question 14

internal factors that regulate growth

Answer 14

plant growth regulators:
produced and secreted from: meristem
how transported: through vascular tissues in the stem
active in small amounts

Question 15

how plant growth regulators and hormones in animals are alike

Answer 15

slow response and transmission speed
produced in one site and active in another
effect is widespread (in more than one part of the plant)

Question 16

types and use of plant regulators: growth promotors

Answer 16

auxins
site of production: shoot tip + root tip
site of action: zone of elongation
example: indoleacetic acid (IAA)

Question 17

auxins function

Answer 17

involved in phototropism (regulatory) and apical dominance (inhibitory)
higher concentration causes more growth, faster rate of cell division

Question 18

IAA

Answer 18

indoleacetic acid
site of production: meristem tissue at root tip and shoot tip
functions: causes stem and root lengthening
stimulates fruit formation

Question 19

describe apical dominance

Answer 19

apical bud produces auxin
auxin moves down through vascular tissue
allows the plant to grow vertically by inhibiting lateral bud growth and side branching

Question 20

mechanism of response : phototropism

Answer 20

stimulus: sunlight
1. IAA produced in meristem
2. diffuses to shady side of stem
3. cells on shady side elongate more than the sunny side (more IAA present)
4. stem bends toward the sun

Question 21

causes of unequal distribution of auxin

Answer 21

shoot: light shining in different directions

causes auxin to diffuse to shady side

Question 22

types and use of plant regulators: growth inhibitors

Answer 22

ethene

abscisic acid

Question 23

ethene

Answer 23

inhibitor
site of production: ripe fruit
functions:
-promotes ripening of fruits
-promotes leaf fall and plant aging

Question 24

abscisic acid

Answer 24

inhibitor 
site of production: stem, leaves
functions:
-inhibit germination: allows germination
-cause stomata to close in dry conditions and retain water

Question 25

commercially prepared growth regulators

Answer 25

gibberellins: production of seedless fruit ethene: ripening of fruit, breaks down chlorophyll

Question 26

benefits of plant growth regulators to horticulturists

Answer 26

promote ripening seedless fruit formation micropropagation

Question 27

micropropagation

Answer 27

rapid multiplication of a plant using tissue culture methods which produce large numbers of identical plants

Question 28

advantage of phototropism

Answer 28

plant grows toward light providing more energy which increases photosynthesis rate

Question 29

advantage of geotropism

Answer 29

ensures roots always grow down to the soil | anchor the plant

Question 30

advantage of chemotropism

Answer 30

stimulates the pollen tube growth leading to fertilisation during sexual reproduction

Question 31

advantage of thigmatropism

Answer 31

provides support to plant for growth eg ivy on tree

Question 32

advantage of hydrotropism

Answer 32

allows plant roots to absorb more water

Question 33

positive tropism

Answer 33

growth response towards the stimulus benefits as it provides best growing conditions eg positive geotropism, roots grow with gravity

Question 34

negative tropism

Answer 34

growth response away from the stimulus | eg negative geotropism, shoots grow against gravity

Question 35

plant adaptations for protection

Answer 35

structural or anatomical adaptations chemical adaptations why: protection against ingestion by herbivores, disease from pathogens, water loss

Question 36

structural/anatomical adaptations

Answer 36

1. spines, thornes -stop animals from eating them eg cacti, nettles 2. guard cells -change shape when they lose water, stomata close controls transpiration rate

Question 37

chemical adaptations

Answer 37

1. toxic chemicals/poisons - kill pests that eat them 2. heat shock proteins - protect enzymes at high temperatures/pH outside optimum range - allow proteins to fold correctly 3. stress proteins: response to invading pathogens - damage micro organisms/ form a strong cell wall to stop the pathogen

Question 38

results of experiment in control

Answer 38

the roots and shoots have grown as the seed itself has produced IAA depending on the concentration of IAA solution, the roots and shoots in the control are longer than those that inhibited growth, and shorter than those that stimulated growth

Question 39

roots after experiment

Answer 39

lower conc. - stimulation, more growth | higher conc. - less growth

Question 40

shoots after experiment

Answer 40

lower conc. - less growth | higher conc. - stimulation

Question 41

experiment

Answer 41

plant used: cress seeds why serial dilution: IAA works at very low concentrations so must be diluted, small amounts are difficult to make safety: wear gloves when handling IAA as it is toxic

Question 42

control

Answer 42

no IAA just distilled water