Physical Defenses Evolve

Thorns, spines, and prickles are the obvious defenses, but plants also deploy trichomes — microscopic hair-like structures that work in radically different ways across species. Some trap insects in sticky secretions, others inject toxins, and some simply make a leaf too rough to chew.

Stinging nettles use hollow silica-tipped needles that break off in skin and inject a cocktail of histamine, serotonin, and formic acid. The plant manufactures hypodermic syringes at the molecular level — a defense you can feel for yourself.