Humans can’t survive more than a few days without water, but some plants, in particular mosses, can survive drought for decades and suddenly revive with the first rain.
When there’s no rain, Tortula mosses dry out completely and stop photosynthesizing. That is, they stop using carbon dioxide and the light of the sun to grow. They’re virtually dead, reduced to a pile of chemicals, and can stay that way for years.
Researchers have found dry, 100-year-old moss samples in a museum that came back to life when water was added. These mosses’ unique ability to survive months, or even years, without water and then spring back to life when it rains has led scientists at UC Berkeley and around the country to study them carefully. They call them “resurrection plants.” They hope to use their genes to create crops that could survive dry periods, like California’s current historic drought, with minimal water.
KQED’s “Deep Look” team visited UC Berkeley’s University to learn about these so-called “resurrection plants.” “Deep Look” is a new ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios.
These mosses are very good at repairing their damaged cells, and that’s a skill that would serve crops well. Right before they dry out, the mosses write themselves a set of genetic instructions, so that if they ever get water again they can start growing right away. Their ability to prepare themselves beforehand and repair themselves after a dry spell reminds the researcher of what humans do to prepare for natural disasters.
They have identified close to 80 genes from Tortula that allow the mosses to write genetic instructions and repair themselves. They called these genes rehydrins.
Researchers have looked inside the crops themselves to see if they don’t already contain some of these moss genes, left over from 450 million years ago, when a common ancestor of mosses and crop plants moved onto land and acquired the ability to live without water.
But using moss genes to make crop plants better able to survive dry spells is a big challenge, in part because this ability comes not from a single gene, but likely from a group of genes.
Another challenge is balancing drought-protection with the need for high yield. It turns out that there really is no free lunch: mosses’ useful ability to live without water makes it hard for them to grow very big.
The cellular mechanism that a plant needs in order to live without water slows down its productivity, measured by the amount of new green tissue a plant can grow. That’s why many plants shed their ability to live without water in favor of an increased ability to grow big.
Plants that can hold water inside their bodies are able to grow big. So if we try to make a crop plant more like a moss its yield will decrease. That’s why researchers’ goal isn’t to make a crop that can live entirely without water, like a moss, but rather a plant that could repair itself after a dry period, even if some yield were lost in the process.
“The idea would be to get the crops to recover as fast as possible so that they can get back to generating biomass or seeds as quickly as possible.”
