DNA is an elegant molecule. Purified, it strings like spider silk. Glassy clear, it hides reams of secrets: though we know its code—ATGC, the letters of its alphabet—we can't yet read it like a book. We may know what it says, but not what it means.

Yet a book is what the genome, the entire set of DNA in an organism, is often called: "life's instruction book," as the title of this year's Penn State Lectures on the Frontiers of Science put it.

Plants can't run away.

It's not a new thought: Anyone has pondered it who's watched a favorite oak stripped by caterpillars, a row of lettuces nipped by frost, or potted pansies wilting in the sun.