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Flashcards in Responding to the environment: Plants Deck (61)
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1

What are plant hormones?

Molecules that are produced naturally within plants.

2

Do plant hormones occur in high or low concentrations?

Low concentrations

3

What do plant hormones do?

Regulate the processes within the plant:

  • In cells and tissues, they influence:
    • growth
    • development
    • differentiation
  • Determine:
    • formation of:
      • flowers
      • stems
      • leaves 
    • shedding of leaves
    • development and ripening of fruit

4

Do all plant cells respond to hormones?

No

5

Name the three different classes of plant hormones

  • Abscisic acid
  • gibberellins
  • auxins

6

Where do auxins occur in the plant?

In the:

  • Embryo of seed
  • Young leaves
  • Young fruit
  • Meristems of apical buds

7

What are some of the major functions of auxins?

  • Stimulate:
    • cell elongation
    • ethylene synthesis
    • fruit development
    • adventitious roots on cuttings
  • Tropic responses (phototropism and geotropism)
  • In vascular tissue, maintains:
    • apical dominance
    • differentiation
  • Inhibits flowering
  • Abscission before formation of abscission layer
  • Controls:
    • ageing
    • senescence
    • dormancy of seeds

8

Where does abscisic acid occur in plants?

  • leaves
  • stems
  • green fruit

9

What are some of the major functions of abscisic acid?

  • Stomatal closure
  • inhibits cell growth
  • dormancy

10

Where is gibberellin found?

  • meristems of apical buds
  • roots
  • young leaves
  • embryo

11

What are some of the major functions of gibberellin?

  • cell division
  • cell elongation
  • shoot elongation
  • seed germination
  • flowering in biennials
  • production of hydrolytic enzymes (in grains)
  • development of male flowers in monoecious plants

12

What do herbicides contain?

a synthetic plant growth hormone or auxin

13

Chemically, what are auxins or plant growth hormones classified as?

acids

14

In what form are herbicides applied?

Ester or salt form

15

What do herbicides induce?

Uncontrolled plant growth

16

What are broad-leaf plants called?

dicotyledons

17

Give one example of a dicotyledon

dandelions

A dicotyledon is a broad-leaf plant

18

What are narrow-leaf plants called?

monocotyledons

19

Give two examples of monocotyledons

grasses

cereal crops

 

Monocotyledons are narrow-leaf plants

20

Which are more susceptable to auxins, dicotyledons or monocotyledons?

dicotyledons

21

What are normally dicotyledons?

weeds

22

What are SELECTIVE HERBICIDES or SELECTIVE WEED KILLERS?

Herbicides that kill some plants, but not others

That are collectively called growth substances

23

What is the most important group of chemicals for plant growth?

Auxins

24

Where are auxins produced?

In the meristematic region of the growth tip of a:

  • shoot or root
  • plant embryo
  • young fruit
  • young leaves

25

Auxins move away from a...

Unidirectional light source

26

Auxins are attracted by...

The force of gravity

27

When auxins occur in the correct concentration, they...

  • stimulate cell division
  • stimulate cell elongation

28

What is phototropism?

The growth response of a plant to a light source

29

What is the growth response of a plant to light source due to?

An unequal distribution of auxins in the stem tip when exposed to a light source from one direction

30

What is positive phototropism?  Where does it occur?

  • Growth towards a light source
  • Plant stems