The desert has long been that lonely, barren place where prophets of old have sought answers to life’s most profound questions.
Professor of Biology Doug Bruce and colleagues have approached the desert with a life question of their own: how are desert green algae able to survive – and even regenerate – in places of severe drought?
The answer is important for understanding how crops and other plants will cope in a world that’s becoming increasingly warmer and more drought prone.
And, far from being barren, the desert is a good place to look for green algae.
Bruce is collaborating with Zoe Cordon, a world expert on these desert green algae. Cordon is senior scientist at the Ecosystem Center in the Marine Biological Laboratory in Woods Hole, Mass.
The team’s project, “Photoprotection in Diverse, Desiccation-Tolerant, Desert Green Algae and Their Close Aquatic Relatives,” aims to determine how desert green algae can protect its ability to undergo photosynthesis under very dry, or desiccated, conditions.
Desert green algae live in “desert crusts” on the ground’s surface that contain a host of microorganisms. These crusts stabilize desert soils, increase water filtration and add nutrients to the soil.
“A variety of microorganisms work together to survive because they don’t have a lot of water,” Bruce explains. “They build these little communities that interact slightly below the surface so they’re protected from the direct sunlight.”
Normally, plants need water to undergo photosynthesis, a process in which the plant converts sunlight and carbon into sugars used for energy.
If deprived of water for a certain amount of time, plants may still look green but are unable to complete the process of photosynthesis; over a longer period of time, the plant eventually dies.
“If you took a piece of lettuce and you dried it out completely and put it in the sun, it would bleach out,” Bruce explains. “In no time, the pigments would be destroyed; photosynthesis would be over. You can pour water over it to bring it back to life, but it’s not going to happen.”
But, desert green algae has “this trick of protecting themselves, so they can survive desiccation and then in the presence of water, come back to pretty-much instantly do photosynthesis,” says Bruce, referring to the times when desert landscapes become green after a rainfall.
Desert green algae do not share the same ancestry as common green plants such as flowering plants, evergreen conifers, mosses, and ferns.
Scientists believe that these terrestrial plants evolved from a single green algal ancestor that came from the water and was able to successfully thrive on land.
But certain types of algae such as desert green algae did not come from that same ancestor and evolved independently of what was to become plants.
Bruce and his colleagues are looking at similarities and differences in the traits of terrestrial plants and green algae.
“One of the aspects of this would be to try to determine if these other lines of green algae that have now shown the ability to withstand desiccation and see what they may have that our crop plants have long, long, since lost or never had at all,” he says.
“Is there a way, then, to think about making crop plants potentially more desiccation-tolerant or at least be able to have some more drought resistance?” he wonders.
In a related area, Bruce notes how aquatic algae grown in ponds and/or bioreactors in the desert can be used to produce a wide array of health products. He gives the example of Israel, which is developing a thriving industry of skincare products, dietary supplements and even biodiesel fuels created from various algae grown in the desert.
