Ali Shayanfar, Bita Oskouei,
Volume 12, Issue 1 (9-2025)
Abstract
Objective: This study aimed to simulate the effects of thermal shocks from crop residue burning and soil temperatures on the germination and dormancy of flixweed (Descurainia sophia) seeds under laboratory conditions.
Method: A factorial experiment was conducted based on a completely randomized design with four replications. Heat shock treatments were applied to flixweed seeds at 80°C and 120°C for durations of 2.5 and 7.5 minutes. Subsequently, the treated seeds were incubated for 14 days under constant temperatures of 7, 15, 20, 25, 30, and 35°C, as well as under an alternating temperature regime of 20/30°C (16h/8h). Various seed germination and dormancy indices were then recorded and analyzed.
Results: The optimum temperature for flixweed seed germination was 7°C. Increasing the germination temperature to 35°C significantly reduced both the germination percentage and rate, while significantly increasing the percentages of dead and dormant seeds. Compared to constant temperatures above 7°C, alternating temperature treatments combined with light exposure enhanced the germination rate and percentage and decreased seed dormancy. Both elevated substrate temperatures and heat shock treatments increased the percentage of dead seeds, particularly at 30 and 35°C under the 120°C heat shock treatment. The highest percentage of normal seedlings was observed at 7°C and under the 20/30°C alternating temperature regime. Applying an 80°C heat shock for 2.5 minutes improved both the germination percentage and rate, and reduced secondary dormancy compared to the control at the same incubation temperature. In contrast, heat shocks at higher temperatures (120°C) led to increased seed mortality and reduced both germination and dormancy.
Conclusions: Heat shock treatments did not induce secondary dormancy (thermo-dormancy) in flixweed seeds; instead, they primarily influenced the germination percentage, germination rate, and seed mortality. The induction of secondary dormancy in flixweed seeds was observed only as a result of elevated substrate temperatures above 7°C. Thermo-dormancy caused by exposure to higher temperatures can be mitigated through alternating temperature treatments combined with light, thereby enhancing both the germination percentage and rate.
Highlights
- The response of the flixweed soil seed bank to crop residue burning was simulated under laboratory conditions.
- Secondary dormancy induction in flixweed seeds was assessed in response to both heat shock and incubation temperature treatments.
- Thermo-dormancy in flixweed seeds was induced exclusively by elevated substrate temperature, not by heat shock treatments.
