Thanks for the interesting question!
Plants can react to their environment in rich
and varied ways called tropisms. Like
animals, plants can detect different stimuli, and
then react accordingly – just usually in a much
longer amount of time than it takes for animals.
For instance, plants have a special cell called a
statocyte that can detect the direction of
the pull of gravity. On the basis of the pull of
gravity, the plant then sends its roots in the
direction of gravity (the ground) and its leaves
in the opposite direction (the air). This is
Plants can also detect sunlight, and will tend to
grow towards the light (phototropism). Some
plants will even turn over the course of the day
to face the sun. Other plants can detect
touch, and change their shape in response.
Other plants have stems that will bend towards
water (hydrotropism). You can see, then,
that plants have evolved these different behaviors
to better find sunlight (for energy) and soil (for
nutrients and water).
Thanks for the great question,
That depends on the plant, and on the
surroundings. Most plants can sense the
direction of light and grow leaves in that
direction, or the direction of gravity and grow
roots in that direction. Some plants, such as pine
trees, can respond to attacks by pests and send
out chemicals that tell other plants of the
attack, allowing the other plants to mount their
own defenses against these pests.
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