Purdue Univ. researchers have found a genetic mutation that
allows a plant to better endure drought without losing biomass, a discovery
that could reduce the amount of water required for growing plants and help
plants survive and thrive in adverse conditions.
Plants can naturally
control the opening and closing of stomata, pores that take in carbon dioxide
and release water. During drought conditions, a plant might close its stomata
to conserve water. By doing so, however, the plant also reduces the amount of
carbon dioxide it can take in, which limits photosynthesis and growth.
Mike Mickelbart, an
assistant professor of horticulture; Mike Hasegawa, a professor of
horticulture; and Chal Yul Yoo, a horticulture graduate student, found that a
genetic mutation in the research plant Arabidopsis
thaliana reduces the number of stomata. But instead of limiting carbon
dioxide intake, the gene creates a beneficial equilibrium.
“The plant can
only fix so much carbon dioxide. The fewer stomata still allow for the same
amount of carbon dioxide intake as a wild type while conserving water,”
said Mickelbart, whose results were published in the early online version of
the journal The Plant Cell. “This shows there is potential to reduce
transpiration without a yield penalty.”
Mickelbart and Yoo
used an infrared gas analyzer to determine the amount of carbon dioxide taken
in and water lost in the Arabidopsis
mutant. Carbon dioxide is pumped into a chamber with the plant and the analyzer
measures the amount left after a plant has started to take up the gas. A
similar process measures water lost through transpiration, in which water is
released from a plant’s leaves.
Analysis showed that
the plant, which has a mutant form of
the gene GTL1, did not reduce carbon
dioxide intake but did have a 20% reduction in transpiration. The plant had the
same biomass as a wild type of Arabidopsis
when its shoot dry weight was measured.
“The decrease in
transpiration leads to increased drought tolerance in the mutant plants,”
Yoo said. “They will hold more water in their leaves during drought
stress.”
Of the 20 genes known
to control stomata, SDD1 was highly
expressed in the mutant. SDD1 is a
gene that is responsible for regulating the number of stomata on leaves. In the
mutant, with GTL1 not functioning, SDD1 is highly expressed, which results
in the development of fewer stomata.
Mickelbart said the
finding is important because it opens the possibility that there is a natural
way to improve crop drought tolerance without decreasing biomass or yield. He
said the next step in the research is to determine the role of GTL1 in a crop plant.
The National Science
Foundation and a Binational Agricultural Research and Development Award funded
the research.
