The latest canola hybrids are able to stand the heat better than their predecessors, but other agronomic factors need to be right to maximize yield.
Murray Hartman, Alberta’s provincial oilseed specialist, said if growers understand what is happening to the plant when the mercury rises, they will be better able to create conditions to help the crop resist damage.
The Lacombe agronomist said when producers see stems that don’t have branches and pods or misshapen pods, it could be linked to earlier symptoms of bud blasting due to episodes of high heat.
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“In cereals, we know that the head forms at tillering, but in canola, it starts at the three to four leaf stage. So heat can start to cause problems at a very early stage,” Hartman said.
If the crop is planted in early May, it isn’t an issue but 2010 is not a typical year, with many crops planted in early to mid June when heat can be a problem for the small plants’ emerging reproductive parts as well as the flowers.
Once the pollen is stuck to the stigma and the pollen tube grows out to meet the pollen and begins hydrating and providing nutrition, the pollen tube transports it to the eggs. Fertilization is underway.
Pollen tubes are the fastest growing part of the plant and will reach the papilla of a stigma in minutes to hours, ready to take in the pollen. This is where significant damage from heat and wind occurs.
The tubes can be injured by extremes of weather or nutrition problems. Ovules can also be damaged in heat, even if those parts have escaped heat or other stresses when the plant was still sexually immature, said Hartman.
Pods elongate from two to eight days and will grow only to a length needed to support fertilized seeds.
If conditions are difficult during flowering, pods will be short. If the conditions improve later in the flowering season, large pods will appear.
“From the stage just prior to bolting, during green bud and up to a week after flowering, they are the most vulnerable to extreme weather, including wind,” said Hartman.
He said the plants have 50 percent more capacity, so canola is adaptable to stress conditions.
Heat stress can also appear as fat, kinked bloated pods. This is a result of odd hormone production that comes in the form of a cascade of plant chemicals that create mutations.
Pistil-like structures and sprouted seeds in pods are also observed and were thought to be caused by herbicide damage but the plant’s own chemicals were to blame.
Hormone cascades created by sudden increases in temperature might cause the plants to abort the crop of flowers to protect the plant during tough weather conditions. Instead, it will try to set flowers again after the heat has passed, said Hartman.
He said producers can try to improve conditions for the crop in years where stress hits early. For 2010, the lateness of crops, washing away of nutrients like nitrogen and sulfur and water stress have left the crop out of time.
For late crops or those with excess water, Hartman advises accepting financial losses rather than investing in crops that are in poor condition.
