Quirks & Quarks

Plants glue on sand for armour

Sand on leaves, stems and flowers discourages hungry herbivores

Sandy coating protects plants from herbivore predation

Sand stuck to the leaf of a Sand Verbena plant (Eric LoPresti)
For more than a century, botanists have noticed that some plants in arid, sandy environments acquire a coat of sand. The sand sticks to the plants because of a sticky, sap-like liquid that they exude, which can have many functions. It hasn't been clear, though, whether sand-coating was incidental, provided some benefit to the plants, or created difficulties for them.

Eric LoPresti, a graduate student in ecology at the University of California, Davis, set about answering this question by studying two plants native to California and finding out whether removing their sandy coating, or adding more sand, helped or hurt them.

He found that a liberal coating of sand considerably discouraged herbivores, such as insects, snails and jack-rabbits, from browsing on the plants, while those plants from which sand was removed were experienced more browsing, presumably because the sand is unpalatable and hard on teeth or other mouth-parts.

Related Links

Paper in Ecology
Newsweek story
Discover story