Plants' Invisible Armor
Plants can't flee from danger, so they've evolved complex defense mechanisms. They produce a variety of chemical compounds that deter herbivores, prevent infections, or even attract predators of their attackers.
Thorns and Trichomes
Physical barriers like thorns protect plants from being eaten. Trichomes, tiny hair-like structures, can be sticky or toxic, deterring insects and animals by causing irritation or delivering harmful substances.
Plants synthesize a vast arsenal of chemical deterrents. Some, like alkaloids and cyanogenic glycosides, target herbivores' nervous systems, while others, like tannins, make the plant less digestible.
When under attack, some plants release volatile organic compounds to signal nearby plants. This 'SOS' can induce the neighbors to preemptively strengthen their defenses or attract the herbivores' natural enemies.
Mimicry and Camouflage
Surprisingly, plants use mimicry and camouflage as defenses. Some may mimic other less palatable plants or even the appearance of diseased foliage, discouraging herbivores from feasting on them.
Many plants have mutualistic relationships with animals. Ants, for example, are attracted by nectar and in return, they defend the plant from other insects and sometimes even prune competing vegetation.
Memory and Learning
Recent studies suggest plants may 'remember' previous attacks and respond more vigorously if attacked again, showing a primitive form of learning typically not associated with organisms lacking a nervous system.