From my first week at the Noble Research Institute, I’ve been growing and taking care of several flats of Setaria viridis, more commonly known as green foxtails. I cleaned their seeds, placed them in petri dishes to germinate, planted them, and individually watered each with a cocktail of nutrients and varying concentrations and sources of nitrogen. I’ve watched the plants fed with the normal amount of nitrogen thrive in their little pots, and the ones starved of nitrogen make a valiant effort to poke through the sand, clay and pearlite that make up their substrate.
By the time the plants started to form panicles and enter the final stage of their life cycle, I thought I’d gotten to know the anatomy of the grass species pretty well. Then, on the day of our microscopy training, I got the chance to take a closer look at the samples I’d been growing.
In the scanning electron microscopy room, Ana Garcia, Ph.D., helped me stick pieces of my sample’s flower, seed and leaf onto a mount, which was then placed inside a vacuum chamber. We opened up a program on the computer, which projected a live video of what was picked up by the microscope. On the lowest magnification, the leaf we oriented beneath the objective lens look fairly normal. Then, as I increased the magnification to 100X, I was shocked by what showed up on the screen. I saw a close-up view of sharp-looking thorns on the leaf surface, so tiny you couldn’t guess they’d be there just looking with your naked eye.
I rubbed the surface of the leaf, wondering why the thorns were there if they weren’t big enough for an animal to notice. Could they function to keep tiny leaf-eating bugs away? Or were they just a left-over artefact of evolution? In biology, it’s hard to find concrete answers to "why" questions, but they’re too interesting not to ask.
Close-up view of Setaria leaf from under the scanning electron microscope.
10-day-old Setaria viridis
Jessi Hennacy adjusting 10-day-old plants for photographing.
Jessi Hennacy is a 2015 Lloyd Noble Scholar in Plant Science from Columbia, Maryland. She is a junior at Duke University, majoring in Biology. Her summer project is studying the expression levels of different ammonium transporters under different soil nitrogen conditions.