Plants’ natural wax may protect from frost

Infrared thermal imaging done at the University of Saskatchewan shows frost development in plants at different temperatures. | U of S photo

A thin layer of cuticular wax found on some plants can repel water, making it harder for the freezing process to occur

Researchers at the University of Saskatchewan are taking a molecular look at cuticular waxes to determine if their presence on agricultural crops can act as a protective layer against frost damage.

Researchers led by Karen Tanino, a professor of plant sciences who specializes in plant physiology, say a thin layer of cuticular wax found of the surface of some plants can repel water, making it harder for the freezing process to occur.

The research team’s findings were published recently in the International Journal of Molecular Science.

“Water is required to make ice. You need low temperatures and you need water,” said Tanino.

“So when there’s less water that’s available for freezing, then even when the temperature is reduced, the surface of the leaf will not freeze.”

Tanino’s research looked at frost development on different plant variants in the Arabidopsis family, which includes canola and mustard.

Three different variants were examined — one that was deficient in a certain type of cuticular wax, another that had normal levels of the wax, and a third that had excessive amounts.

The three variants were placed in a phytotron, a device that allows researchers to expose plants to a variety of temperatures and environmental conditions.

As the plants were exposed to lower temperatures, infrared thermal-imaging cameras were used to detect heat loss.

When water freezes, it releases heat.

In essence, the infrared cameras that detected heat loss were confirming the beginning of the freezing process.

“We found that plants that were deficient in certain types of cuticular waxes were freezing at warmer temperatures — about two degrees warmer,” Tanino said.

“And those that had an excess of that wax were freezing at lower temperatures — again, about two degrees lower.”

“Even a two degree difference can be really critical in the field….”

Results were similar when the research team looked at water loss under hot conditions.

“It reinforced our thinking that these particular components in the cuticular layer are important not just to one stress but to multiple stresses.”

Cuticular waxes are a mixture of long-chain, water-repelling fatty acids.

The longer the chain, the greater the wax’s water-repelling properties.

In some instances, foliar sprays with super-hydrophobic properties have been applied to high-value horticultural crops as a means of preventing frost damage under low temperatures.

For broad-acre crops such as canola, wheat, barley, or oats, it remains to be seen whether foliar sprays could be used to protect against frost.

But Tanino’s research suggests that it may be possible to select plant lines based on their ability to produce cuticular wax.

This would allow plant breeders to develop new crop varieties that are more tolerant to low temperatures and less prone to water loss under extreme heat.

“There are enzymes and biochemical pathways that upregulate this wax biosynthesis,” Tanino said.

“So, if breeders and molecular geneticists can identify the target and then select from tens of thousands of potential pathways, they may be able to develop more climate adaptive plants a lot sooner in a lab than by exposing them to whatever stress exists in the fields.”

Tanino said plants that produce higher levels of water-repelling long-chain fatty acids do not appear to have any productive disadvantages vis a vis plants that produce lower levels of cuticular wax.

More waxy plant types do not appear to have reduced yield potential.

Tanino’s research team also used the mid-infrared beamline at the Canadian Light Source synchrotron in Saskatoon to study Arabidopsis leaves at a depth of two microns, or two one-thousandths of a millimetre.

Data obtained provided information on the quantity and quality of the plants’ surface wax.

In an interview with The Western Producer, Tanino said selecting waxy cultivars and developing new waxy crop varieties could be a key to protecting commercial grain crops from costly frost-related losses in the spring and fall.

Tanino’s lab has been examining plant physiology to look for ways to enhance “stress avoidance” in agricultural crops.

Scientists at the lab are interested in avoiding the impacts of both abiotic stresses — such as heat, drought and frost — as well as biotic stresses, which include diseases and insect pressures.

“In any given year in the field, you never know whether drought stress, or disease, or insects, or frost, or heat stress is going to be the prevailing stress,” Tanino said.

“If we can find ways to protect plants against multiple stresses… they’ll be hopefully a bit more productive.”

While numerous studies have established the role of cuticular wax in impacting drought resistance, few studies have examined its role in plant frost resistance and even fewer have examined both.

Funding for Tanino’s research was provided by the Natural Sciences and Engineering Research Council (NSERC), the Saskatchewan Ministry of Agriculture, and the Saskatchewan Wheat Development Commission.

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