Plant Hormones

Question 1

Examples of plant abiotic stress

Question 2

deciduous plants response to abiotic stress

Answer 2

lose all leaves and become dormant in winter due to low temperature and light intensity

Question 3

why do deciduous plants become dormant in winter

Answer 3

glucose requried for respiration is greater than can be made in photosynthesis

Question 4

plant response to abiotic stress: daylight sensitivity

Answer 4

determined by light sensitive pigment phytochrome
responses include: breaking dormancy, timing of flowering

Question 5

define photoperiodism

Answer 5

the sensitivity of plants to lack of light

Question 6

plant response to abiotic stress: abcission

Answer 6

auxin concentration falls with light intensity
ethene stimulates enzyme production that weakens cell walls of the base of leaves

vascular bundles sealed, fatty material seals where leaf fell (scar)

Question 7

plant response to abiotic stress: prevent freezing

Answer 7

cytoplasm and vacuole contain solutes that lower freezing point

Question 8

plant response to abiotic stress: stomatal control

Answer 8

Hormone ABA controls stomatal closure. when water potential is low binds to guard cell receptors closing stomata

Question 9

plant response to herbivory: physical defences

Answer 9

thorns, spiny leaves, fibrous inedible tissue, stings

Question 10

plant response to herbivory: tannins

Answer 10

phenol in leaves, bitter taste and toxic to insects

Question 11

plant response to herbivory: alkaloids

Answer 11

eg. caffeine and nicotine
taste bitter, can affect metabolism
caffeine is toxic to fungi and insects

Question 12

what are pheromones

Answer 12

chemicals produced by an organism that affects the social behaviour of members of the same species

Question 13

plant response to herbivory: pheromones

Answer 13

produce VOC when attacked

Question 14

plant response to herbivory: folding in response to touch

Answer 14

leaves collapse scaring herbivores and dislodging insects

Question 15

define tropism

Answer 15

the turning of all or part of an organism in a particular direction in response to an external stimulus.

Question 16

phototropism

Answer 16

the growth of plants in response to light from one direction only

Question 17

how do auxins control phototropism and growth toward light

Answer 17

auxin concentration on shaded side is high stimulating cell elongation and growth causing the shoot to grow directly towards light

Question 18

geotropism

Answer 18

the growth of plants in response to gravity

Question 19

how does geotropism affect plants

Answer 19

shoots: negatively geotropic
roots: positively geotropic
shoots grow up towards light, roots grow further into soil

Question 20

what is germination

Answer 20

the process by which a plant grows from a seed

Question 21

how do gibberellins aid seed germination

Answer 21

seed absorbs water activation the embryo
embryo produces gibberellins
stimulates enzyme production to break down food stores
food stores produce ATP allowing embryo to break out of seed coat

Question 22

function of auxins

Answer 22

control cell elongation
inhibit abcission
apical dominance
phototropism
stimulate ethene release
fruit ripening

Question 23

function of gibberellins

Answer 23

stem elongation
food store mobilisation

Question 24

function of ethene

Answer 24

fruit ripening
abcission of deciduous leaves

Question 25

function of ABA

Answer 25

stomatal closure maintains seed and bud dormancy stimulate antifreeze production

Question 26

what are auxins and where are they made

Answer 26

growth stimulants produced in the roots, shoots and meristem

Question 27

role of auxins

Answer 27

stimulate main apical shoot growth high concentrains inhibit lateral shoot growth

Question 28

positives of apical dominance

Answer 28

plants grow verically taller and are able to compete for sunlight and other resources

Question 29

how do gibberellins aid stem elongation

Answer 29

increase internode length due to more cell elongation in stems

Question 30

commercial use of plant hormones: control of ripening

Answer 30

ethene is used to aid ripening of fruit after hervesting eg. bananas, tomatoes and mangoes ripens by triggering a series of chemical reactions that increase respiration rate

Question 31

commercial use of plant hormones: rooting powders

Answer 31

applying auxins to cut stem stimulates growth of roots allowing plants to be grown from cuttings

Question 32

commercial use of plant hormones: hormonal weed killers

Answer 32

imbalance of plant hormones disrupts plant metabolism and can lead to plant death

Question 33

other commercial uses of plant hormones

Answer 33

auxins: production of seedless fruit ethene: stimulate fruit dropping cytokinins: prevent aging of ripe fruits gibberellins: delay ripening