UNIT: 3 Response In The Flowering Plant

Question 1

stimulus

Answer 1

anything that causes a response in an organism

Question 2

response

Answer 2

activity of an organism or part of an organism as a result of a stimulus

Question 3

growth regulator

Answer 3

chemical that controls the growth of a plant

Question 4

tropism

Answer 4

growth response of a plant to a stimulus

Question 5

phototropism

Answer 5

growth of a plant in response to light

Question 6

geotropism

Answer 6

growth response of a plant to gravity

Question 7

thigmotropism

Answer 7

growth response of a plant to touch

Question 8

hydrotropism

Answer 8

growth response of a plant to water

Question 9

chemotropism

Answer 9

growth response of a plant to chemicals

Question 10

auxin

Answer 10

a growth promoter e.g. indole acetic acid (IAA)

Question 11

production sites of auxins

Answer 11

auxins are produced in the meristematic tissue of shoot tips and root tips

Question 12

functions of auxins

Answer 12

• stimulates cell elongation
• stimulates cell division
• differentiation of meristem cells into xylem and phloem
• apical dominance
• delaying of fruit ripening
• phototropism and geotropism

Question 13

mechanism of a plant tropism - phototropism

Answer 13

• IAA is produced in the apical meristem of the shoot.
• this diffuses down the shaded side of the stem.
• this causes cell elongation on the shaded side.
• the shaded side of the stem grows more quickly than the exposed side of the stem.
• this causes the shoot to bend towards the source of light.

Question 14

uses of plant growth regulators

Answer 14

• naphthalene acetic acid (NAA) is used as a commercial rooting powder.
• ethene is used as a ripening agent for fruit.

Question 15

anatomical adaptations for protection

Answer 15

• epidermis - protects against pathogens entering the plant
• guard cells - protect against excess water loss.
• some plants have bark - to protect against herbivores.
• cacti have evolved to have no leaves (to protect against water loss) and spikes (to protect against herbivores).

Question 16

chemical adaptations for protection

Answer 16

• corn lily produces a toxin called cyclopamine to protect itself against herbivores.
• many plants produce alkaloids that protect against insects and herbivores.
• poison ivy produces a chemical called urushiol that protects against herbivores.
• conifers produce monoterpenes that protect against many insect herbivores.