• Question: How do plants defend themselves?

    Asked by anon-356041 on 30 Mar 2023.
    • Photo: Liz Barron-Majerik

      Liz Barron-Majerik answered on 30 Mar 2023:

      Plants have both physical and chemical defences which are really important as when a herbivore comes along they can’t just run away. They need to keep their leaves safe as it takes energy and resources to make them, and they need the leaves to capture energy from the sun. So sometimes they have spines or hairs (makes it physically harder to eat) or chemicals are released when an animal brushes them (nettles) or sometimes the chemicals are inside the plant and just make the leaf taste really bad!

    • Photo: Sam Mugford

      Sam Mugford answered on 30 Mar 2023: last edited 30 Mar 2023 8:24 am

      One of the neatest ways that plants defend themselves is by calling for help. When a plant is having it’s sap sucked by an aphid, or being chewed by a caterpillar, the plant releases smells (volatile chemicals). These smells attract enemies of the aphids and caterpillars including ladybirds that love to eat aphids. They also attract parasites of aphids including very small parasitic wasps that lay their eggs inside the aphids or caterpillars. Here’s a video of a wasp laying its eggs inside an aphid:

      the eggs hatch out inside the aphid, and the wasp larvae grows and eats the aphid from the inside out, and eventually an adult wasp burst out of the dead aphid.

    • Photo: Annis Richardson

      Annis Richardson answered on 30 Mar 2023:

      Plants have lots of ways defend themselves. Physical things like spikes, spins, thorns, prickles and hairs, chemicals that make the leaf toxic or taste bad (caffeine is one of these!), volatile chemicals that make the plant smell bad to herbivores and insects (e.g the way a tomato plant smells) or that can signal to predators to attract them. Also the volatile signals can tell other plants nearby that they are under attack and to get ready. The wax on the surface of the plant is also really important to prevent things like viruses, bacteria and fungi getting into the plant cells. If they get through this protective layer there are lots of back-up mechanisms to try to fight the invader using chemicals and enzymes.

    • Photo: Sharon Mithoe

      Sharon Mithoe answered on 30 Mar 2023:

      Plants have developed many clever mechanisms to defend themselves against environmental changes, herbivores and attacks by pathogens. Their first line of protection is a physical barrier such as a waxy outer layer, thorns, spines, nettles. Plants are sessile meaning that they are not mobile, but for survival they utilise rapid responses through their complex defence system when under attack from pathogens and produce anti bacterial chemicals that can kill bacteria. Plants are very clever and their defence system is so complex that we are doing research to understand and puzzle the different parts together.