Some plants use chemical protection. The ability of a
plant to produce and retain toxic substances in its tissues gives it considerable
evolutionary advantage over its less toxic relatives.Many poisons—as well as many useful pharmaceuticals—are
derived from plants, including hemlock, strychnine, curare, digitalis, nicotine, and many
hallucinogens. Some of these chemicals are extremely toxic, and can cause injury and even
death in very small doses; others have curative powers in small doses but are lethal at
higher doses.
Instead of, or in addition to, producing toxic substances,
some plants produce chemicals that make them taste bitter, sour, or otherwise unpalatable.
However this doesn’t always prevent them from being eaten. Humans, in their
fascinating and sometimes bizarre attraction to the shocking or unpleasant, take advantage
of many plants’ chemical deterrents. Witness the popularity of fiery hot peppers,
astringent wines and teas, cigarettes and cigars, and caffeinated coffee!
But these deterrents to would-be devourers aren’t the
only forms of chemical protection. Other plants use different tactics:
- Black walnut tree roots produce a chemical called juglone
that inhibits growth of nearby plants. This form of chemical protection is termed allelopathy.
- Stinging nettles have special epidermal "stinging
hairs." When these hollow, needle-shaped hairs are touched, the brittle cap on the
gland breaks off, causing a stinging acid to be injected into would-be diners—or an
unwary passerby.
These are just a few examples of the many interesting
adaptations plants use to fill their basic needs and protect themselves. Now let’s
look at some of the ways plants have adapted to various climates, and how they synchronize
themselves to the changing of the seasons.
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