• Question: Do you know how the water gets from the ground up through the stem and is used by the plant for nourishment?

    Asked by zaina to Amy, Karen, Sarah, Vijay, Will on 11 Jun 2012.
    • Photo: Sarah Martin

      Sarah Martin answered on 11 Jun 2012:

      Hi Zaina, great question! 🙂

      There are two main things that drive water up the stem, against gravity. The first is an effect caused by the surface tension of water, called the capillary effect. This occurs in thin tubes (like in the stem of plants) and makes water rise up thin tubes to decrease the tension in its surface. There’s a great experiment that you can do yourself in class, which allows you to see capillary action really well:

      The other effect works like a straw. When water evaporates from the surface of leaves (which it does, that’s why rainforests are often misty!), it’s the same effect as when you suck at the top of a straw and more of your drink enters the straw from the bottom – more water is sucked up at the roots!

      Here’s a lovely video of a plant recovering from having too little water – capillary action in action!

    • Photo: Amy Birch

      Amy Birch answered on 11 Jun 2012:

      Well there’s certainly nothing more for me to say about how the water gets into the plant’s stem & leaves!
      Plants use the water in photosynthesis – they use sunlight to convert carbon dioxide & water to sugar & oxygen.
      I’m growing 3 chilli plants on my windowsill at the moment, so I hope it gets sunny again soon!

    • Photo: Karen Reed

      Karen Reed answered on 12 Jun 2012:

      roughly but not in detail. Check out Sarah’s answer who’s covered it in detail

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