Changes in Seed Oil Profile and Morphological Characteristics in Sunflower Cultivars Under Salinity Stress and Nanoparticle Treatments

This study investigated the effects of zinc oxide and iron oxide nanoparticles and two salinity levels on the morphological characteristics and seed fatty acid profiles of two sunflower hybrids (G1601 and Shams). The research aimed to understand the impacts of these treatments/stresses potentially leading to strategies for improving crop resilience in water-scarce environments, especially considering their potential roles as fertilizers and stress mitigators. This experiment utilized a randomized complete block design with a factorial arrangement (nanoparticle type, salinity levels, hybrid type, and age) of five treatments (50 and 150 mM salinity, 20 ppm ZnO and Fe₂O₃ nanoparticles, and control samples) with 20 replications. Morphological measurements for the root, leaf, stem, and seed dimensions were taken using a digital caliper. For both hybrids, seed priming with Fe₂O₃ nanoparticles resulted in the highest root dimensions, while 150 mM salinity stress led to the lowest values for these parameters. For both hybrids, the highest and smallest yielded seeds belonged to the control and 150 mM salinity-stressed plants, respectively. In the G1601 hybrid, salinity stress (50 mM) produced the largest leaves, whereas Fe₂O₃ in second, third, and sixth week and ZnO nanoparticles in fourth and fifth week resulted in the smallest. In the Shams hybrid, the smallest leaves were recorded for the Fe₂O₃ nanoparticles treated in first to fourth week and the control plants in fifth to seventh week, while the biggest leaves belonged to the control in first to second week and ZnO nanoparticles treated samples in third, fifth, and seventh week. The Shams hybrid seed oil analysis showed linoleic acid as the dominant fatty acid (63.29%–72.98%), followed by oleic acid (15.33%–22.78%). Conversely, the G1601 hybrid seed oil was characterized by oleic acid as the primary fatty acid (46.54%–80.34%), with linoleic acid presented at a lower percentage (8.67%–40.29%). In the Shams hybrid, oleic acid amount significantly increased in all the treated/stressed samples, except for those that were subjected to 50 mM salinity stress. Conversely, linoleic acid amounts decreased in these salinity-stressed samples. Meanwhile, in the G1601 hybrid, linoleic acid content increased significantly, while oleic acid content decreased in the treated/stressed samples. Additionally, the total percentages of saturated and unsaturated fatty acid amounts changed under these treatments/stresses. The responses of sunflower plants to nanoparticles and salinity stresses were not uniform; they varied based on several factors, including the plant's genetic structure (hybrid type), age, and the specific type of nanoparticle or salinity treatment/stress applied. Developing more tolerant sunflower hybrids requires understanding how different treatments affect fatty acid biosynthesis involved genes and how hybrids respond differently. Therefore, investigations into the effect of various treatments/stresses and expression of involved genes are recommended for future works.