How to Make See-Through Flora—for Science

A chemical that alters chlorophyll makes green plants transparently easy to study.

This story appears in the May 2017 issue of National Geographic magazine.

The inside workings of plants are the unexplored frontier of botany. What happens when a nematode or fungus attacks a crop? How does this stress affect the plant, and how does it physically change the roots, stem, and flowers?

Japanese researchers have devised a way to find out: Make the plant transparent. With a chemical bath, they reduce the plant’s visible chlorophyll, the pigment that makes it green. Days to weeks later the entire plant becomes clear, and scientists can observe its inside tissue at a cellular level.

Death is part of the process. While the plant is still alive, researchers introduce genes for fluorescent proteins, then kill the plant with formaldehyde to freeze the processes the researchers want to study. The method yields information broadly useful in plant research—about reproduction, for instance. Understanding exactly how a plant selects one of the hundreds of grains of pollen that land on a pistil can help breeders propagate better apples or peaches—or any other crop that reproduces by pollination.

So far researchers have tested the transparent effect on rice, tobacco, tomato, cucumber, moss, and other flowering plants. But this sort of botanical x-ray can be applied to anything that sprouts. “Any researcher can use it,” says project lead Daisuke Kurihara, a plant cell biologist at Nagoya University, “and the plant’s interior can be clearly observed and analyzed in detail.”

– With Takao Fujiwara

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