Developing Heat-Tolerant Cotton in Arizona
Plant physiologist Steven J.
Crafts-Brandner inspects a
cotton plant that will be used
in a heat-stress experiment.
Scientists in Phoenix are
studying plants that thrive in extreme climates to help them produce better
cotton in Arizona. These plant physiologists want to see what internal
processes allow plants to grow in harsh climates and then apply the information
to develop cottonand perhaps some other cropswith improved ability
to grow in very hot, dry places, like Arizona.
Several years ago Michael E. Salvucci and Steven J. Crafts-Brandner of the
ARS Western Cotton Research Laboratory
began studying the properties of rubisco activase, a plant enzyme that helps
photosynthesis work properly. (See "Robust Plants'
Secret? Rubisco Activase!" Agricultural Research, November
2002.) They found that the enzyme, and thus photosynthesis, does not operate
effectively if the crop is grown out of its native environment and subjected to
They have now taken this knowledge to the next step. They compared plants
from various regionsdesert shrubs, Antarctic grasses, temperate spinach,
and subtropical cottonto see how the enzyme works under a variety of
conditions. "We found that the enzyme from plants native to warmer regions
is inherently more stable in high temperatures," Salvucci explains. They
also found the opposite: Rubisco activase in plants native to colder regions is
more stable in lower temperatures.
Thanks to plant breeding and irrigation, commercially grown cotton produces
very high yields. But yields could be even higher, particularly in the
Southwest, if photosynthesis did not shut down in the heat. With the knowledge
obtained from their research, the scientists believe they may be able to
manipulate the enzyme in cotton to improve heat tolerance and thus produce more
bountiful yields in Arizona.
The Southwest is dry as well as hot, and water is valuable. Normally, cotton
performs best when its leaves are at 82°F. When air temperature rises above
that point, cotton leaves can be cooled by transpirationevaporation of
water from their surfaces.
The research conducted at the cotton lab may help cotton grow with less
water, because tolerance of higher leaf temperatures means that less water
needs to be used in cooling the leaves. The research could also apply to
growers in other parts of the country who rely on rainfall and whose cotton can
be wiped out by a severe drought.
The researchers are currently putting the gene for rubisco activase from a
desert shrub into cotton. They want to test their hypothesis that the altered
cotton will better tolerate Southwest heat, producing greater yields with less
water. "We're developing a potential cure for the heat-stress problem by
examining how desert plants cope with the temperatures of their native
environment," Salvucci says.
In the future, other crops besides cotton may be grown successfully outside
their traditional temperature- and water-limited production areas.By
Elstein, Agricultural Research Service Information Staff.
This research is part of Plant Biological and Molecular Processes, an ARS
National Program (#302) described on the World Wide Web at
"Developing Heat-Tolerant Cotton in Arizona" was published in the November 2004 issue of Agricultural Research magazine.