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Dry Times

Dry Times
Images from a thermal camera show that the German Arabidopsis plants transpire less and are hotter (bottom three). This contrasts with the German plants that have a key section of chromosome from Cape Verdean plants. They transpire more and are much cooler (top three).

Images from a thermal camera show that the German Arabidopsis plants transpire less and are hotter (bottom three). This contrasts with the German plants that have a key section of chromosome from Cape Verdean plants. They transpire more and are much cooler (top three).


Any farmer or gardener worth their salt understands the power of water to give life and to take it away. And plants vary widely in their adaptations to a life with water or the lack thereof—think desert-dependent cacti versus swamp-loving cypress trees

Arabidopsis is interesting to Juenger because it has adapted to environmental extremes. Populations range from the icy cold climates of northern Scandinavia—where the plant behaves like a “winter annual” and can lie dormant under the snow—to the dry, hot coasts of northern Africa—where it’s a short lived spring annual.

“This plant has had to solve lots of problems in terms of invading new habitats and dealing with climatic variation,” says Juenger. “We just view that natural variation like a ‘mutant pool.’ A traditional geneticist would knock out or over express a gene to try to understand its function. What we’re doing is looking at natural genes that have already been through the adaptive sieve.”

His work is becoming more critical as breeders and engineers race to make better drought-ready crops, as climate change and increased urban growth put greater pressures on water availability.

Juenger and his students have seen that some Arabidopsis plants escape drought by simply flowering early. Others shut their leaves down and stop photosynthesis during drought. Still others will simply wait until the water returns.

“Our goal now is to figure out what genes control this variation,” says Juenger.

In one of his biggest projects, he’s studying plants from Cape Verde (off the coast of Africa) that release a lot of water vapor from their leaves, and plants from Germany that transpire much less. By crossing the plants and mapping their genes, Juenger has identified a small section of one of the plant’s chromosomes that’s responsible for these differences.

Plants with the Cape Verdean chromosome section (and its genes) are transpiring more than those without it, and these plants’ leaves are several degrees cooler than plants without that section of chromosome. Transpiration, like sweating, leads to cooler body temperatures, but also loss of water, which is not necessarily a good thing in times of drought.

“We’re probably a year from knowing what the particular gene or genes responsible for this are,” says Juenger, confidently. “Maybe two.”

The thing to realize, he says, is that drought adaptation is going to be affected by many genes and their interaction with environmental conditions.

“It would be naïve to think we could use molecular biology to make a silver bullet to cure plants of drought stress,” says Juenger. “But if we do want to make a plant that performs better, why not let nature tell us how it engineers a plant with high water use efficiency?”

This article also appeared in the Spring 2009 issue of Focus magazine.

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Monday, 19 April 2021

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