Plants are attacked by myriad herbivores, and many plants exhibit anti-herbivore defences. A new research discovered that tomato plants may induce insects to increase cannibalism behaviour in order to protect themselves.
The new study has been conducted by John Orrock, Brian Connolly and Anthony Kitchen and published on Nature Ecology & Evolution. They tested the hypothesis that induced defences benefit tomato plants by encouraging insects to eat other members of their species.
What happens exactly?
Plants don’t stay passive when they interact with herbivores: they alter their chemistry, morphology and other components of their phenotype – in other worlds they change – to reduce herbivory. More specifically, they make their leaves (or other parts) less nutrient for the insects. Because of the lack of food, insects get more stressed and start to eat each other more or earlier than usual. Such behaviour, allows tomato plants to benefit in two ways:
- cannibalism directly reduces herbivore abundance,
- cannibals eat significantly less plant material.
Further more, it’s been observed that plants release chemicals to warn other plants of the threat. It means they use cues from their environment to initiate these defences. This is a sign for insects predators too, as if the plants are informing predators of the presence of their preys (and food).
Knowing that, the team sprinkled undamaged tomato plants with airborne chemical cues, such as methyl jasmonate (MeJA) and jasmonic acid, with the aim to cause changes in their defence. At the end of the experiments, over five times as much plant biomass remained, clearly demonstrating the value that plants can receive by inducing defences before an actual attack, thanks to high levels of MeJA.
On the contrary, plants in control – with a low MeJA treatment – start their defence once an attack – by insects – is under way and it’s been observed that it’s then too late and many of these plants were entirely consumed.
In conclusion, this study can be exploited to develop chemicals that can induce these changes in defence and, by consequence, can cause an increased insects cannibalism. This process will eventually keep the plants more protected and boost their spread.