How Plants Defend Themselves

Plants are at the very bottom of the food chain, but that doesn’t mean that they don’t do what they can to protect themselves from predation by herbivores. The most basic protective strategy is to grow in remote or harsh climates not conducive to herbivores, avoiding them altogether. Given that such environments tend not to be particularly conducive to plants either, most plant species have evolved other ways to evade being eaten too easily, or too entirely.
The most common plant survival strategy is to simply offer up their most non-essential or easily-replaced parts for consumption—most often their tender, nutritious leaves, which animals (including humans) generally prefer to the more indispensable yet tougher stem sections. Herbivores are intent on a good meal, after all, not the destruction of the plant which provides it, and most herbivores’ grazing patterns indicate an innate understanding of how much of a plant can be eaten without it being killed. In conditions where a plant’s resources, such as food and water, are scarce, the cost of replacing damaged leaves can be great. Plants that grow in these areas tend to invest more resources into anti-herbivore defenses, the spiny exteriors of desert cacti being excellent examples. Other physical or “mechanical” defenses would include the armored seeds of coconuts and the tough, glossy leaves of holly.
Many plants have also developed chemical defenses. These generally consist of toxins either contained in or produced by plants to sicken, paralyze, or even kill would-be herbivores. Certain plants also deploy chemicals to lure “enemies of their enemies”—natural predators of the herbivores who try to eat them. This strategy is most effective against a plant’s primary threats: insects, which inhabit a steeply tiered food chain all their own.

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