• Question: how do plants defend themselves from diseases?

    Asked by to Amelia, Clem, Izzy, Sarah on 18 Mar 2014. This question was also asked by .
    • Photo: Sarah Harvey

      Sarah Harvey answered on 18 Mar 2014:

      I love that you’ve asked this as it’s what I’m currently trying to work out with my research!

      We don’t know as much about how plants defend themselves as we know about human or animal immune systems but we know they have several layers of defines:

      1) Physical barriers, akin to our skin etc, plants have waxy cuticles and hairs on their leaves which are the first layer any potential bugs have to get past.

      2) Antimicrobial compounds which already exist

      3) Defenses which are activated upon recognition of disease – so like we have antibodies in our blood which recognise invaders, plants have a way of recognising ‘non self’ too. Insead of antibodies they have ‘pattern recognition receptors’ at their cell membranes which basically detect microbes, and they do this by recognising conserved bits, for example bacteria have flagella which are basically tails that allow them to swim and plants can recognise these and therefore know they’re being infected by bacteria. Clever huh!

      4) Once they know they’re being invaded plants have various things they can do, one method they use is by killing the cells around the invasion so that the microbes can’t get any nutrients and the infection stops. Plants can also produce more antimicrobial chemicals and physical barriers to stop them moving and spreading throughout the plant.

      5) It then gets very complicated because the bacteria/microbes try and attack the plant immune system, and this is what I work on 😀

    • Photo: Isabel Webb

      Isabel Webb answered on 18 Mar 2014:

      Plants have a very smart system of signalling to tell itself that it is being attacked. It then has many different strategies.

      One is to create a barrier to letting bacteria in – such as hairs on the leaves. However, plants still have pores called stomata on their underside of the leaves which bacteria can sneak through, so the physical barriers can’t completely stop them.

      One of the first things that the plant does is work out how far into the plant a disease has come. If a single leaf is in infected, often the easiest thing to do is to sacrifice that leaf for the good of the plant. This is why you might see a single dying brown leaf on an otherwise healthy plant – the plant just cuts off any supplies to the leaf and lets it die.

      Sometimes the plant has to make a decision – do I use my energy to grow, or to fight the invasion. If they make the wrong choice they could die. Our bodies often make the choice to divert energy to fighting infections which is why we get really tired when we are ill.

Comments