Plants and Light

Question 1

What is tropism?

Answer 1

A plants growth in response to environmental cues.

Question 2

What is growth?

Answer 2

A permanent increase in the size of an organism or of some part of it.

Question 3

Where are the main areas of stem elongation?

Answer 3

The meristem. These are areas which occur just behind the tip of a root or shoot and are particularly sensitive to chemical messages produced in a response (in particularly) to light.

Question 4

What happens when one side of a plant grows more than the other?

Answer 4

It results in the bending of shoots or roots in response to a particular stimulus.

Question 5

What does chlorophyll formation depend on?

Answer 5

Light and day length (or night length). These environmental cues determine changes such as bud development, flowering, fruit ripening and leaf fall.

Question 6

What is photoperiodism?

Answer 6

Plants flower and seeds germinate in response to changes in day length.

Question 7

What is phototropism?

Answer 7

Tropisoms are growth responses in plants where the direction of the growth response is determined by the direction of the external stimulus.

Question 8

What is meant by ‘positive tropism’?

Answer 8

When growth of plant is towards stimulus.

Question 9

What is meant by ‘negative tropism’?

Answer 9

When growth is away from the stimulus.

Question 10

What is the name of the photoreceptor you’re supposed to know that is involved in light conversion?

Answer 10

Phytochrome.

Question 11

What is phytochrome?

Answer 11

A blue-green pigment which exists in two interconvertible forms; Pr which absorbs red light and Pfr which absorbs far red light.

Question 12

Which is more stable, Pr or Pfr?

Answer 12

Pr but Pfr is more biologically active.

Question 13

How is Pfr converted to Pr?

Answer 13

When it’s exposed to far red light (rapid) or via slow conversion in the dark.

Question 14

How is Pr converted to Pfr?

Answer 14

Via red light (rapid).

Question 15

Which is inactive? Pr or Pfr?

Answer 15

Pr.

Question 16

What is the critical day length?

Answer 16

The length of daylight which appears to be needed to trigger flowering in plants.

Question 17

What are short day plants?

Answer 17

Plants which need long periods of darkness (short days) to trigger flowering. Red light inhibits flowering of short-day plants but if red light is followed by far red light, the inhibition is lifted.

Question 18

What are long day plants?

Answer 18

Plants which require short periods of darkness (long periods of light) to trigger flowering are known as long-day plants. Require

Question 19

What are day-neutral plants?

Answer 19

Plants where the flowering is not affected by the length of the periods of dark or light.

Question 20

What part of the plant does the detection of photoperiod seem to happen?

Answer 20

The leaves of the plant (which is a photoreceptor).

Question 21

What experiment can be done to study phototropism?

Answer 21

Question 22

What is plant growth hormone? What is an example?

Answer 22

Plant hormones, chemicals which control growth in plants. Auxin. (IAA).

Question 23

What do auxins do? Where are they made?

Answer 23

They stimulate the growth of shoots by cell elongation. They’re made in the tip of the shoot.

Question 24

What happens if there’s a high concentration of auxins?

Answer 24

Plant growth is inhibited.

Question 25

Summarise the role of auxins in the growth of plant shoots.

Answer 25

Question 26

What occurs in the shoot tip when there light is beging distributed equally?

Answer 26

An even distribution of auxins moves down the shoot tip and causes elongation of cells across the zone of elongation.

Question 27

What occurs at the shoot tip (and zone of elongation) when it is exposed to light unilaterly (is that even a word)?

Answer 27

Auxins move down from the shoot tip towards the shaded side of the shoot. Only those cells on the shaded side are elongated and the shoot bends towards the light.

Question 28

Compare the communication and coordination methods in plants and animals.

Answer 28