9.1 Plant Structure and Growth Flashcards Preview

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Flashcards in 9.1 Plant Structure and Growth Deck (37)
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31

State the location of lateral meristems

Formed from the cambium cells

32

Outline the function of apical meristems

Responsible for primary growth
Increases height/depth of plant
Produces new leaves and flowers

33

Outline the function of lateral meristems

Responsible for secondary growth
Increases girth of stem for strength
Produces bark on trees

34

Define tropism

Bending growth of a plant towards or away from a directional stimulus

35

Define phototropism

Bending growth of a plant towards a source of light

36

Define auxin

A group of substances that promote plant growth

37

Explain the role of auxin in phototropism

• Auxin makes plant cells enlarge and grow
• Auxin causes cell elongation by activating pumps that expel H+ ions from the cytoplasm into the cell wall
• The resulting decrease in pH within the cell causes cellulose fibres to loosen, as the bonds which hold them together are broken
• This makes the cell wall flexible and capable of stretching when water influx promotes cell turgor
• In the shoot, auxin is eradicated by light
• The greater presence of auxin on the shaded side of the plant causes this side to lengthen, making the shoot curve towards the light