With over
300,000 plants species on Earth, there's no doubt that they have highly
developed
senses to
stay alive and thrive. But while some of their features may be compared to
taste, sight, touch and smell in humans, have you ever wondered - can plants
think?On land, the cumulative mass of plants is 1000 times higher than that of
animals. But these plants are immobile and can't move around in their
environment; which is, seemingly, a pretty big evolutionary disadvantage. This
has forced plants to adapt in amazing ways that often go unnoticed by the naked
eye. Smell something funny? Plants do too - and they react to these chemicals
in the air. For example, when fruits start to ripen, they release a chemical
called ethylene. And when neighbouring fruits sense this pheromone, they ripen
faster, so that all fruits mature at the same time. Plants also give off scents
which attract insects to spread their pollen. In particular, the amazing
carrion flowers grow tiny hairs, feel warm and smell like
rotting
flesh in an attempt to mimic a dead corpse. This is to attract flies and beetles
as pollinators. On the other hand, when a plant is attacked by an insect,
animal or pathogen, it knows. When acacia trees are grazed by animals, they
quickly react by producing chemicals called tannins, which make their leaves
unappetizing and tough to digest. Some even produce enough toxin to kill the
animal. Perhaps more impressive are some corn and cotton plants, which when
eaten by caterpillars, release chemicals in the air that attract parasitic
wasps, who
fly in
and ultimately kill the insects. On some level, they communicate with the wasps.
Crazy as it seems, even sound recordings of caterpillars chewing leaves,
trigger this response. Without any form of touch, the plants react, as if they
can hear. On a large scale, plants also work together. A web of underground
fungi can connect tree roots in forests, allowing them to exchange nutrients
and information. Using radioactive isotopes, scientists discovered that trees
share water and nutrients with others in need. Large trees nourish smaller
shaded ones until they are tall enough to reach sunlight, and trees that stay
green all year round share nutrients with trees that lose their leaves in
winter - helping them through the season. Which is then repaid in the summer months,
like a transactional exchange. Some scientist refer to this as the 'wood-wide web’.
Perhaps the most shocking fact, is that some plants seem to have memory. Mimosa
pudica plants, are those leafy plants that close up when touched. This reflex
is meant to scare away insects that land on them. In an experiment on these
reflexes, scientists notice that when dropped from 15cm they would close when
they hit the group. Not so surprising. But after repeating the drop 4 or 5
times, some of the plants stopped closing, as though they had realized the
stimulus wasn't harmful. If they were shaken instead, they would close, but any
time they were dropped from this same height, they stayed open. This effect lasted
for weeks - the plants had memories. Of course, plants don't have brains or
other cells and organs that we deem necessary for intelligence. Brains and
neurons are irreplaceable, but plants are immobile and often attacked, so they
must be able to survive after part of them is eaten, or destroyed. A brain just
wouldn’t work. But if you measure intelligence or thought as the ability to
solve problems, interact with an environment, and even work in groups, then
plants are incredibly smart. It’s something to think about next time you're
munching down on a piece of broccoli!
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