plant responses

Question 1

define stimulus

Answer 1

anything that causes a reaction in an organism or any of its parts

Question 2

whats an animal stimulus

Answer 2

includes feeling pain/hunger, hearing a noise

Question 3

whats a plant stimulus

Answer 3

light, gravity, temperatures

Question 4

define response

Answer 4

the action pf a cell/organism as a result of a stimulus

Question 5

give an example of an animal response

Answer 5

movement, production of enzymes and feeding

Question 6

give an example of a plant response

Answer 6

growth, flowering

Question 7

what is needed structurally for response

Answer 7

chemical/hormonal system (plants and animals), nerve and sense organ system, method of movement, immune system

Question 8

what do plants depend on for their response

Answer 8

chemical co-ordination

Question 9

define tropsim

Answer 9

a chenge in the growth of a plant in response to an external stimulus

Question 10

define positive tropism

Answer 10

when the growth is towards the stimulus

Question 11

define negative tropism

Answer 11

when the growth is away from the stimulus

Question 12

what is the advantage of tropisms in a plant

Answer 12

they allow plants to obtain favourable growing contidtions

Question 13

what is phototropism

Answer 13

change in growth in a plant in response to light

Question 14

are stems positively phototropic

Answer 14

yes… allows the plant to get more sunlight

Question 15

are roots positively phototropic or negatively phototropic

Answer 15

most are neg… e.g ivyy

Question 16

what is geotropism

Answer 16

the change in growth of a plant in response to gravity

Question 17

are roots positively geotrophic

Answer 17

yes, they grow downwards

Question 18

are stems positvely geotrophic

Answer 18

no they are negatively geotrophic… grow against gravity

Question 19

whats the benefit of roots growing towards gravity

Answer 19

can anchor the plant better, absorb water + minerals better

Question 20

whats thigmotropism

Answer 20

the change in growth of a plant in response to touch

Question 21

give an example of a plant that uses thigmotropism

Answer 21

climbing plants e.g ivy, vines, peas

Question 22

what do positively thigmotropic plants grow to climb

Answer 22

tendrils which have positive thigmotropism

Question 23

what’s hydrotropism

Answer 23

the change in growth of a plant in response to water

Question 24

define chemotropism

Answer 24

the change in grwoth of a plant in response to chemicals

Question 25

give an example of positive chemotropism

Answer 25

roots grow towards minerals… pollen tubes grow towards chemicals from the ovule

Question 26

what might make a root negatively chemotropic

Answer 26

presence of harsh acids or heavy metals in soil e.g zinc/lead

Question 27

what is a growth regulator

Answer 27

chemicals that control the growth of a plant

Question 28

where are grwoth regulators mainly produced

Answer 28

meristem region

Question 29

how are growth regulators transported

Answer 29

vascular tissues

Question 30

give an example of a growth regulator which is a growth promoter?

Answer 30

auxins, e/g indoleactic acid (IAA)

Question 31

what is the name given to a regulator that slows down plant growth

Answer 31

growth inhibitor e.g abscisic acid

Question 32

where is IAA produced?

Answer 32

shoot tips, young leaves and seeds

Question 33

give 3 functions of auxins

Answer 33

stimulate stem elongation and root growth, develop fruit, inhibit side branching in stems, cause phototropism and geotropism, cause cells to grow into different structures

Question 34

what are some effects of auxins

Answer 34

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)

Question 35

explain apical dominance

Answer 35

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

Question 36

explain the mechanism of a plant’s response to light

Answer 36

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

Question 37

what is the only growth regulator that is a gas

Answer 37

ethene gas

Question 38

where is ethene gas used

Answer 38

to commercially ripen bananas

Question 39

what is the role of ethene in a plant

Answer 39

causes fruit colour to form, fruit flavour to develop and fruit tissues to soften

Question 40

name a growth inhibitor and state where it is produced

Answer 40

absisic acid… produced in leaves, stems and root caps

Question 41

what is a stress regulator and give an example

Answer 41

absisic acid… causes plants to respond to harmful conditions

Question 42

give an example as to how absisc acid helps regulate stress in plants

Answer 42

dry conditions it causes stomata to close in order to conserve water

Question 43

name some comercially prepeared growth regulators

Answer 43

rooting powders(naphtyacetic acid), tissue culturing, ethene

Question 44

list some structural adaptations in plants for protection

Answer 44

plants enclosed by a physical barrier e.g epidermis,bark,stingning hairs… guard cells close stomata when lack or water

Question 45

list 2 chemical adaptations of plants for protection

Answer 45

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