The secret senses of african plants - part 2 - Safari in Kenya

The secret senses of african plants. Part 2

I’ve already talked about the secret senses of the plants and some of their strategies to survive in a recent post, but there would be much a lot to say about it.. I have only barely touched on the subject.

Today, in fact, I wish to take in consideration other interesting aspects of this topic.

In the other post I referred to Daniel Chamowitz book, What A Plant Knows: A Field Guide to the Senses and I talked about smell and how african acacias communicate each other using this sense to defend themselves.

AUGUST 2020

Plants
Africa
Acacia

Now, there is another excellent example of plant communication through smell and it happens when fruit ripens.

Plants face many environmental challenges and one of them is seed dispersion. Many plants produce fruits attracting animals to eat them. The seeds are usually well protected and go through the animal’s digestive system without being harmed, emerging with a good dose of fertilizer away from the parent tree. If a tree “wants” baboons to disperse its seeds, it has to produce enough ripe fruits for the whole troop, which means the fruits have to ripen at the same time. This ripening is induced by a chemical called ethylene which is produced by the ripening fruits.

Probably you know that, if you want an apple to ripen quickly, you have to put it in a bag with a ripe banana, for example. The apple will “smell” the ethylene being produced by the banana and will be stimulated to ripen quickly.

Saimiri or Squirrel monkey (Saimiri sciureus) – Central and South America

Bonobo (Pan paniscus) – Congo

Another amazing example of plants communicating using the sense of smell is in a defensive way. I have already treated this topic in another post, talking about the way the acacias defend themselves from herbivores.

But what if the “predator” is not a mammal, but a bacteria or an insect?

Leaf beetle (Chrysomelidae)

A study on Lima beans or butter beans (Phaseolus lunatus), a plant found in Meso and South America, has revealed that the plant reacts by producing different chemical compounds depending on who is the predator. If the plant is attacked by a bacteria it produces a compound called methyl salicate that stimulates a specific defense reaction. If, instead, it is a herbivore mammal the plant produces methyl jasmonate (the same chemical acacias produce to increase tannin levels in their leaves). And in case the plant is attacked by an insect, like aphids or beetles, it produces another chemical to attract a type of wasp, a predator of those insects.

I’ll never stop saying nature is fantastic!

But it is not over!

Black bean aphid (Aphis fabae)

African Monach caterpillar (Danaus chrysippus)

Asclepias (called also milkweed) produces a latex, a sticky and milky substance containing cardiac glycosides which are toxic to many species, included humans. Its scientific names comes from Asclepius, the god of medicine in ancient Greek mythology. This is, once again, an anti-predation strategy. But he African Monarch caterpillars (Danaus chrysippus) evolved in turn and now they are able to feed on these plants and instead of being killed, they are able to accumulate the toxins and taste bad to their predator which will learn and avoid them.

African Monarch (Danaus chrysippus) adult

African Monarch (Danaus chrysippus) caterpillar

At last, another interesting discovery involves an underground communication between plants. Most plants have a mutual relationship with a special kind of fungi, mycorrhizal mycelia, in their root system. These mycelia spread out through the soil and help the trees with getting the nutrients needed and, at the same time, get sugar from the trees. These networks of fungi is able to connect the trees together. There are evidence that fungi even take nutrients from healthy trees and give them to the weak and sick ones. Thing is, if they are able to do such a thing, they can also probably transfer warning signals between the plants.

This discovery is anyway very recent and our knowledge is still restricted. A similar thing, also, has been evoked about the relationship between fungi and termites, but there are not yet scientific evidence.

One thing for sure, there are a lot of really amazing things happening outside there, and not only in Africa, that we can’t see or smell at all.