Microfossil of the Month: Setaria italica tissue phytoliths

Last month I thought that I would be unable to post any new micrographs for a while, however with a stroke of luck, and digging out of an old hard drive, I came across all the files from my PhD thesis! A stark reminder of the importance of proper archiving of digital image files, I must have hundreds of images that have not been catalogued properly...I'll add that to the to do list! Here we have a micrograph of a reference specimen of Setaria italica, more commonly known as foxtail millet. In this image you can see that this is a very well silicified bit of plant tissue, with all the individual cells being clearly defined. This is a leaf fragment and you can see the spikey hair phytoliths, which are also called trichomes. the little 'dumb-bell' shaped short cells are known as bilobes or bilobate cells. These bilobes are typically found in plants with C4 photosynthesis, and can give an indication of the broad type of environment. C4 refers to the biochemical mechanism that the plant uses to obtain and process carbon dioxide from its surroundings. The more common mechanism is known as C3 photosynthesis, and C4 plants have an advantage over C3 plants in environments which are prone to drought, high temperatures and limited carbon dioxide. So if we have a dominance of C4 plants on an archaeological site, this could be interpreted as having a hot, dry environment in the past. However, as with all plants in archaeological contexts, it is important to remember that plants are capable of existing outside their preferred environments, and the presence of C3 plants on site does not necessary reflect local environmental conditions!