Document Type : Research Article
Authors
Department of Plant Production and Genetics, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran
10.22067/jcesc.2024.88492.1335
Abstract
Introduction
Waterlogging is a complex environmental stress limiting crop productivity and yield stability. Waterlogging in crop plants remains a serious barrier to crop production around the globe in high-rainfall areas with heavy rainfall or poor drainage. Waterlogging duration and the growth stage during waterlogging can affect the physiological, biochemical and yield traits of safflower. However, the effects of waterlogging stress at different growth stages on photosynthesis processes and antioxidant defense systems of safflower under field conditions are not yet known. The aim of this study was to identify the most sensitive growth stage of the safflower crop for waterlogging stress to develop our understanding of complex mechanisms underlying waterlogging tolerance in safflower.
Materials and Methods
In order to study the influence of waterlogging duration at vegetative and reproductive stages on the yield, photosynthetic characteristics, and antioxidant activity of safflower, a field experiment was carried out during 2020-2021 growing season in a split-plot arrangement in randomized complete blocks design using three replicates per treatment. The research farm was located at Shahid Chamran University of Ahvaz, Iran. The plants were grown in the field to ensure the environmental conditions found in waterlogged and flooded soils. Three waterlogging treatments were applied to plants as main plots: Well-drained controls watered weekly, mild stress (waterlogged for 24 h) and severe stress (waterlogged for 48 h). Waterlogging treatments were implemented at stem elongation (vegetative stage), and full branching (reproductive stage) as sub plots. Seeds originated from the Seed and Plant Improvement Institute, Karaj, Iran. Before and after the end of waterlogging period, waterlogging treatments were watered with sufficient water (80% field capacity) until the end of the experiment. The data for stomatal conductance, photosynthetic rate, chlorophylle index, catalase, peroxidase and superoxide dismutase enzyme activities, biological yield, oil content, and seed and oil yield was recorded. Gas exchange characters were measured after waterlogging stress and then after 7 days of recovery.
Results and Discussion
The mild and severe waterlogging stress treatments at both vegetative and reproductive stages led to a significant reduction in stomatal conductance (24 and 35%, respectively), photosynthetic rate (49 and 60%, respectively), chlorophyll index (14 and 44%, respectively), biological yield (21 and 27%, respectively), seed (34 and 39%, respectively) and oil yield (16 and 32%, respectively) but increased catalase (7 and 51%, respectively), peroxidase (7 and 35%, respectively) and superoxide dismutase (9 and 17%, respectively) enzyme activities compared to well-drained controls. After 7 days of recovery, gas exchange measurements were recovered in mild and severe waterlogging stress treatments. Plant growth stage and stress duration playe d an important role in the response to waterlogging stress. In severe stress treatment, the activity of antioxidant enzymes; catalase, peroxidase and superoxide dismutase at the reproductive stage was higher than the vegetative stage (26, 17 and 9%, respectively). However, there was no significant difference between growth stages in terms of all traits except for catalase, peroxidase and superoxide dismutase activity. The mild and severe waterlogging stress at both growth stages led to a significant reduction in seed yield by 34 and 39%, and oil yield by 16 and 32% respectively, compared to control. In contrast to the results of antioxidant enzyme activities, the maximum decrease in seed yield was found when waterlogging occurred in severe stress treatment at the reproductive stage. The reduction was 43%, when compared to the control.
Conclusion
The results highlighted that waterlogging during the reproductive stage of oilseed safflower resulted in higher yield loss than during the vegetative stage and these findings emphasized that the impacts of waterlogging stress on oilseed crops are important and the management practices of safflower fields especially in the Khuzestan region must be strengthened during the winter season.
Acknowledgement
We gratefully acknowledge funding support from Shahid Chamran University of Ahvaz grant number SCU.AA99.96
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