Response of canola to different heat stresses
Authors: Aksouh N. M. , Jacobs B. C. , Stoddard F. L. , Mailer R. J. 
Published: September 2002

0 in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40°C heat treatment accelerated plant maturity and
resulted in drastically decreased seed weight, and therefore yield, compared
with the control, whereas the 45 DD/stepped treatment had much less effect
on the 3 lines, particularly Oscar. Oil concentration of the seed was reduced
following the 15 DD/40. The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40h was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40°C heat treatment accelerated plant maturity and
resulted in drastically decreased seed weight, and therefore yield, compared
with the control, whereas the 45 DD/stepped treatment had much less effect
on the 3 lines, particularly Oscar. Oil concentration of the seed was reduced
following the 15 DD/40°C treatment by a half in Range, a quarter
in Monty, and a fifth in Oscar, in contrast to reductions of a third, a tenth,
and nil following the 45 DD/stepped treatment. The 15 DD/40The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40h was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40°C heat treatment accelerated plant maturity and
resulted in drastically decreased seed weight, and therefore yield, compared
with the control, whereas the 45 DD/stepped treatment had much less effect
on the 3 lines, particularly Oscar. Oil concentration of the seed was reduced
following the 15 DD/40. The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40h was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40°C heat treatment accelerated plant maturity and
resulted in drastically decreased seed weight, and therefore yield, compared
with the control, whereas the 45 DD/stepped treatment had much less effect
on the 3 lines, particularly Oscar. Oil concentration of the seed was reduced
following the 15 DD/40°C treatment by a half in Range, a quarter
in Monty, and a fifth in Oscar, in contrast to reductions of a third, a tenth,
and nil following the 45 DD/stepped treatment. The 15 DD/40°C
stress was also associated with much greater increases in protein and
glucosinolate concentrations over control values than the 45 DD/stepped
stress. The 15 DD/40/40h was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40°C heat treatment accelerated plant maturity and
resulted in drastically decreased seed weight, and therefore yield, compared
with the control, whereas the 45 DD/stepped treatment had much less effect
on the 3 lines, particularly Oscar. Oil concentration of the seed was reduced
following the 15 DD/40. The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40h was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40°C heat treatment accelerated plant maturity and
resulted in drastically decreased seed weight, and therefore yield, compared
with the control, whereas the 45 DD/stepped treatment had much less effect
on the 3 lines, particularly Oscar. Oil concentration of the seed was reduced
following the 15 DD/40°C treatment by a half in Range, a quarter
in Monty, and a fifth in Oscar, in contrast to reductions of a third, a tenth,
and nil following the 45 DD/stepped treatment. The 15 DD/40The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40h was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40°C heat treatment accelerated plant maturity and
resulted in drastically decreased seed weight, and therefore yield, compared
with the control, whereas the 45 DD/stepped treatment had much less effect
on the 3 lines, particularly Oscar. Oil concentration of the seed was reduced
following the 15 DD/40. The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40h was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40al of 15
degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40°C,
which was then maintained for 4 h on 5 successive days, giving a total of 15
degree-days of stress (15 DD/40°C). The second treatment comprised
5 days of stepwise increase in daily maximum temperature to 40°C,
giving a total of 45 degree-days above control conditions (45 DD/stepped).
The 15 DD/40°C heat treatment accelerated plant maturity and
resulted in drastically decreased seed weight, and therefore yield, compared
with the control, whereas the 45 DD/stepped treatment had much less effect
on the 3 lines, particularly Oscar. Oil concentration of the seed was reduced
following the 15 DD/40°C treatment by a half in Range, a quarter
in Monty, and a fifth in Oscar, in contrast to reductions of a third, a tenth,
and nil following the 45 DD/stepped treatment. The 15 DD/40°C
stress was also associated with much greater increases in protein and
glucosinolate concentrations over control values than the 45 DD/stepped
stress. The 15 DD/40°C treatment had a pronounced effect on
fatty-acid composition, increasing saturated fatty-acid content and decreasing
oleic acid content, in both Monty and Range but not in Oscar, whereas the 45
DD/stepped treatment had no significant effect on fatty-acid composition.
These results show that although the gradual temperature increase as
implemented in this experiment resulted in a greater degree-days heat load, it
was not as detrimental to quality as a sudden increase. The cultivars varied
in their responses to the heat load.