
TY  - JOUR
A1  - Aksouh, N. M. 
A1  - Jacobs, B. C. 
A1  - Stoddard, F. L. 
A1  - Mailer, R. J. 
T1  - Response of canola to different heat stresses
JF  - Australian Journal of Agricultural Research
JO  - Aust. J.  Agric. Res.
Y1  - 2001
VL  - 52
IS  - 8
SP  - 817
EP  - 824
KW  - Brassica napus, oil, protein, glucosinolate, Australia, tolerance, temperature.
UR  - https://doi.org/10.1071/AR00120 
N2  - 0 in daily maximum temperature to 40al of 15 degree-days of stress (15 DD/40s. One treatment comprised a rapid increase to 40&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;C, giving a total of 45 degree-days above control conditions (45 DD/stepped). The 15 DD/40&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;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&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;C, giving a total of 45 degree-days above control conditions (45 DD/stepped). The 15 DD/40&#176;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&#176;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&#176;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&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;C, giving a total of 45 degree-days above control conditions (45 DD/stepped). The 15 DD/40&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;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&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;C, giving a total of 45 degree-days above control conditions (45 DD/stepped). The 15 DD/40&#176;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&#176;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&#176;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&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;C, giving a total of 45 degree-days above control conditions (45 DD/stepped). The 15 DD/40&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;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&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;C, giving a total of 45 degree-days above control conditions (45 DD/stepped). The 15 DD/40&#176;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&#176;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&#176;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&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;C, giving a total of 45 degree-days above control conditions (45 DD/stepped). The 15 DD/40&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;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&#176;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&#176;C, which was then maintained for 4 h on 5 successive days, giving a total of 15 degree-days of stress (15 DD/40&#176;C). The second treatment comprised 5 days of stepwise increase in daily maximum temperature to 40&#176;C, giving a total of 45 degree-days above control conditions (45 DD/stepped). The 15 DD/40&#176;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&#176;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&#176;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&#176;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. 
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