Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) are antioxidant enzymes which have important role in the metabolic reactive oxygen species (ROS) and defence against oxidative stress damage. Antioxidant enzymes activity increases in plant cells as a response to environmental stresses. The objective of this study was to evaluate the effects of micronutrients application on the antioxidant enzyme metabolism (SOD, CAT and GPX) in sunflower under drought stress. This experiment was carried out at Golmakan Agriculture Research Station (Iran) in 2005, using a split plot randomized complete block design with four replications. Irrigation as a main factor at three levels (normal, low stress and high stress) and six micronutrient treatments (control, Fe, Fe+Zn, Fe+Zn+Cu, Fe+Zn+Cu+Mn, Fe+Zn+Cu+Mn+B) as sub-plots within the main plots. Base fertilizers (N,P,K) and micronutrient treatments also used as required on the basis of the soil test. Results showed that the activity of these enzymes was significantly different (a= 5%) between control and stress treatments. The antioxidant enzymes concentrations were increased at 11-31% under high stress. Also there were significant differences (a= 5%) between control and micronutrient treatments under different enzyme concentrations. The antioxidant enzymes concentrations were increased at 48-89% level with Fe+Zn+ Cu+Mn treatment. The results showed that under drought stress micronutrients application increase drought resistance in sunflower.
Introduction: Velvetleaf is one of the most important weeds of cotton, corn, tomato, and soybean fields. Certainly, knowledge of weed seed response to environmental factors (light and temperature) is essential for better understanding the germination mechanism and establishment patterns of weeds community. The present study aimed to evaluate the interaction between light regimes and alternate temperature on the seed germination of velvetleaf.Materials and Methods: The experiment was conducted in 2015 at the plant physiology laboratory of Bojnourd Branch, IAU. This study was performed as a factorial experiment based on a completely randomized design (CRD) with four replications. The treatments were temperature regimes at four levels (constant temperatures 25C, alternating temperatures 25-15, 30-20 and 35-25C) and photoperiod treatments at three levels (continuous darkness, 12-12 light and dark and 16-8 light and dark). Germination percentage, germination rate, germination uniformity, time to 10% germination, and time to 90% germination were evaluated by the Germin program.Results: The results showed that all traits were affected by temperature and light. Velvetleaf seeds germinated better in the presence of light and alternating temperature. The percentage and rate of germination increased as temperature rised to 30°c and then decreased. However, seed reaction to the night temperature was higher than that of the day temperature. The highest germination percent (98 percent) was achieved under alternating temperature 25-15°C with 12-12h light-dark. In this study, the lowest time required for 10% and 90% germination and highest germination uniformity were observed under alternating temperatures 30-20°C in darkness.Conclusion: According to the results of this experiment, velvetleaf seeds are able to germinate in a wide range of light and temperature conditions, although they germinate better in the presence of light and alternate temperatures. Therefore, plowing with a moldboard plow can stimulate germination and drain the soil seed bank.
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