Sometime after the last ice age, inhabitants of the western hemisphere began to select and cultivate food plants. Plant remains at archaeological sites may not be well preserved, but features often contain phytoliths, tiny silica dioxide deposits from plant tissues. These destinctive microfossils have been used increasingly over the last decade in studies of plant domestication, because they clearly identify a number of different crop plants and their wild progenitors.
However, little is known about how plants make phytoliths, and why.
A 1997 study showed that a single gene in maize controls phytolith production, lignification and silification, all characteristics modified when modern maize diverged from its wild ancester, teosinte.
On the hunch that the same might be true for squash, Piperno and Irene Holst from STRI with Linda Wessel-Beaver from the Univeristy of Puerto Rica and Thomas Andres of the Cucurbit Society set about to characterize the rinds of 148 fruits from wild and cultivated species of the squash genus, Cucurbita. They also crossed the plants and characterized the rinds of their offspring.
Thin sections of the soft rinds of domesticated species lacked lignification and big, scalloped phytoliths. All of the species with hard rinds (both wild and domesticated) were lignified and contained phytoliths.
One to one correnspondence between lignification and the presence of phytoliths plu
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Contact: Dolores Piperno
pipernod@tivoli.si.edu
011-507-212-8101
Smithsonian Tropical Research Institute
30-Jul-2002