• Question: What actually happens to make auxin elongate plant cells?

    Asked by to Amelia, Izzy, Sarah on 19 Mar 2014. This question was also asked by .
    • Photo: Amelia Frizell-Armitage

      Amelia Frizell-Armitage answered on 19 Mar 2014:

      Plants have strong cell walls which hold the plant cell in the right shape. Usually these cell walls are pretty rigid. However, the hormone Auxin causes the bonds that tightly hold cell walls together to break. This means that the cell can actually now change it’s shape and elongate. After it has elongated enough the bonds in the cell wall reform and the cell is again rigid.

    • Photo: Isabel Webb

      Isabel Webb answered on 19 Mar 2014:

      It isn’t actually the cells which elongate – what happens is that new cells are made. Auxin has effects on cell division – more cell division means more cells and so longer.

      Auxin has different effects depending on where it is. In the roots auxin acts to help roots dig downwards by sensing gravity. In shoots it helps move towards the light. In shoots auxin locates itself and increases cell division. In roots it blocks cell division.

      This illustrates why plants are so smart! They know how to respond just bet knowing which bit of the plant they are.

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