Morphological Traits, Yield and Nutrient Uptake of Safflower Cultivars Under Water Stress Conditions

Document Type : Research Paper

Authors

1 Former student of Agroecology, Department of Agroecology, College of Agriculture and Natural Resources of Darab, Shiraz University, Darab, Iran.

2 Assistant Professor, Department of Agroecology, Darab College of Agriculture and Natural Resources, Shiraz University, Shiraz, Iran.

3 Associate Professor of Department of Agroecology, College of Agriculture and Natural Resources of Darab, Shiraz University, Darab, Iran.

4 Technisian of Department of Agroecology, College of Agriculture and Natural Resources of Darab, Shiraz University, Darab, Iran.

Abstract

 
In order to investigate the genetic diversity of safflower cultivars based on yield, yield components, and mineral nutrient uptake under water stress conditions, a factorial experiment was conducted in a completely randomized design with three replicates at the research greenhouse of the Faculty of Agriculture and Natural Resources, Darab, Shiraz University. The experimental factors included three irrigation levels (normal irrigation, irrigation cut off at flowering stage, and irrigation cut off at head formation stage) and seven cultivars (Faraman, Sina, Omid, Padideh, Goldasht, Parnian, and Golmehr). The aim of this study was to evaluate the genetic variation among safflower cultivars in terms of grain yield, biological yield, plant height, 100 seed weight, number of seeds per head, head diameter, number of heads per plant under water stress conditions, as well as to assess mineral nutrient uptake from soil under such conditions. The results showed that the interaction between irrigation levels and cultivars had a highly significant effect (p ≤ 0.01) on all morphological traits, except for the number of secondary branches. The highest grain yield (31 g) was observed in the Parnian cultivar under normal irrigation. Seed yield of all cultivars decreased under water stress conditions, however, the highest yield (15.8 g per plant) in this condition related to Omid cultivar which also had the minimum variations among the cultivars. The results of this experiment showed that the highest genetic variation of cultivars appeared under normal irrigation conditions as well as high variations of nutrient uptakes.

Keywords

Background and Objectives

Water deficiency is a major abiotic stress that severely limits agricultural productivity, particularly in arid and semi-arid regions where crops like safflower are cultivated. Drought stress during critical growth stages can disrupt physiological processes, leading to substantial reductions in yield and alterations in nutrient acquisition. Understanding the genetic variation among cultivars in their response to water deficit is crucial for developing resilient crop varieties. The objectives of this study were to: i) investigate the genetic diversity of seven safflower cultivars under different irrigation regimes, ii) quantify the impact of water stress timing on grain yield, biomass, and morphological traits, and iii) assess how cultivar and irrigation interactions affect the uptake and concentration of key mineral nutrients (Cu, Fe, P, K) in the seeds.

Materials and Methods

A factorial experiment was conducted in a completely randomized design with three replicates at the research greenhouse of the Faculty of Agriculture and Natural Resources, Darab, Shiraz University. The experimental factors included three irrigation levels: normal irrigation, water stress imposed at the flowering stage, and water stress imposed at the head formation stage. These treatments were applied to seven distinct Iranian safflower cultivars: Faraman, Sina, Omid, Padideh, Goldasht, Parnian, and Golmehr. Standard agronomic practices were maintained for all groups except for the targeted water stress treatments. At physiological maturity, the plants were harvested, and data were collected on agronomic traits including grain yield, biomass, and the number of secondary branches. Additionally, seed samples were analyzed using appropriate laboratory techniques to determine the concentrations of copper, iron, phosphorus, and potassium.

Results

The statistical analysis revealed that the interaction between irrigation levels and cultivars had a highly significant effect (p ≤ 0.01) on nearly all measured morphological and agronomic traits. The only exception was the number of secondary branches, which was not significantly influenced by this interaction. In terms of yield, the Parnian cultivar demonstrated superior performance under optimal conditions, producing the highest grain yield of 31 grams per plant and the maximum biomass of 135 grams per plant. However, this cultivar was highly sensitive to water stress, suffering a drastic 58% reduction in grain yield and a 42% decrease in biomass when water was withheld at the flowering stage. The other cultivars exhibited varying degrees of tolerance, but none matched Parnian's yield under normal irrigation or its level of decline under stress. Regarding mineral nutrition, the irrigation-by-cultivar interaction also significantly (p ≤ 0.01) affected all seed nutrient uptake traits. The highest seed concentrations of copper, iron, phosphorus, and potassium were consistently recorded in the Parnian cultivar under normal irrigation. A clear pattern emerged where these optimal nutrient concentrations were significantly diminished across all cultivars when subjected to water stress, with the most severe reductions again occurring due to flowering-stage stress. This indicates that stress timing is critical, with the flowering stage being more detrimental to both yield and nutrient accumulation than the head formation stage.

Conclusion

This study conclusively demonstrates a significant genetic diversity among safflower cultivars in their physiological and agronomic response to water stress. The Parnian cultivar, while high-yielding under optimal irrigation, proved to be highly susceptible to drought, particularly when it occurred during the flowering stage. The findings highlight that the timing of water stress is a critical factor, with the flowering stage identified as the most sensitive period for irreversible damage to yield and nutrient partitioning. The strong interaction effect on seed mineral content further reveals that water stress not only reduces yield but also compromises the nutritional quality of the harvested crop. Therefore, selecting for drought tolerance specific to the flowering stage should be a key breeding objective. For cultivation in drought-prone environments, it is recommended to avoid highly sensitive cultivars like Parnian in favor of more stable, though potentially lower-yielding, alternatives under optimal conditions. Future research should focus on the physiological mechanisms conferring tolerance in the more resilient cultivars to inform marker-assisted breeding programs.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

The study was funded by Shiraz University.

Authorship contribution

 “Conceptualization, A. B. and H. R.; methodology, H. R.; software, H. R.; validation, A. B. and E. B.; formal analysis, H. R.; investigation, H. R.; resources, A. B..; writing—original draft preparation, H. R.; writing—review and editing, A. B.; visualization, H. R. .; supervision, A. B.; project administration, A. B. .; funding acquisition, A. B. All authors have read and agreed to the published version of the manuscript.”

Declaration of Generative AI and AI-assisted technologies in the writing process

Authors declare that they have not used any AI and AI assisted program and technologies in this paper.

Data availability statement

Data of this study are available by email to the corresponding author.

Acknowledgements

The authors would like to appreciate Shiraz University for financial support of this research.

The authors would like to thank anonymous reviewers for their valuable suggestions in manuscript revision. We also would like to thank chief editor of Iranian Journal of Soil and Water Research for his valuable comments during the publication of this paper.

Ethical considerations

The authors avoided data fabrication, falsification, and plagiarism, and any form of misconduct.

Conflict of interest

The authors declare no conflict of interest. 

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Iranian Journal of Soil and Water Research
Volume 57, Issue 4
June 2026
Pages 787-806

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