چكيده انگليسي :
Salinity stress is a critical abiotic challenge for plants, while rising atmospheric carbon dioxide levels, a key indicator of climate change, also significantly impact plant growth. Safflower (Carthamus tinctorius L.), an important oilseed crop with relative salinity tolerance, is a promising candidate for cultivation in saline areas. This study explored the interaction effects of salinity stress, zinc sulfate application, and increased carbon dioxide on the morphological, physiological, and biochemical characteristics of safflower in both field and greenhouse experiments. In the field experiments, salinity stress was induced using sodium chloride at two levels (2 and 12 dS/m), and zinc sulfate was applied via foliar spraying at a concentration of 3% in two stages (at the beginning of flowering and 10 days later) across nine safflower genotypes. Salinity stress reduced grain yield, straw yield, plant height, oil content and yield, relative leaf water content, chlorophyll a, b, carotenoids, Fv/Fm, membrane stability index, water use efficiency, potassium, calcium, zinc, and the potassium-to-sodium ratio. However, it increased levels of malondialdehyde, proline, and the activities of catalase, peroxidase, and ascorbate peroxidase enzymes, along with sodium accumulation. Conversely, zinc sulfate application increased grain yield, straw yield, harvest index, water use efficiency, oil content and yield, zinc content, the potassium-to-sodium ratio, chlorophyll a, b, carotenoids, Fv/Fm, relative leaf water content, membrane stability index, and the activities of catalase, peroxidase, and ascorbate peroxidase enzymes, while reducing malondialdehyde, proline, sodium, and calcium levels. The Arak genotype was identified as superior under field conditions. In the greenhouse experiment, two levels of carbon dioxide (400 and 700 µmol/mol) and three levels of salinity (control, 6, and 12 dS/m) were applied to four safflower genotypes. Increased carbon dioxide levels led to higher dry weight of shoots and roots, root volume, seed weight, oil content, Fv/Fm, relative leaf water content, chlorophyll a, b, carotenoids, membrane stability index, potassium content, potassium-to-sodium ratio, water consumption, and salinity tolerance indices (STI, CSI, YSI), while reducing hydrogen peroxide, sodium, and proline levels. Moderate salinity stress under elevated carbon dioxide conditions increased shoot dry weight, seed weight, water consumption, and salinity tolerance indices, though severe salt stress significantly reduced shoot dry weight in all genotypes except PI-301055, and notably in the Arak genotype. The Koseh and C411 genotypes were identified as superior under greenhouse conditions. Overall, zinc sulfate foliar application appears to be an effective management strategy for mitigating the negative effects of salinity stress in safflower plants, though its efficacy depends on the genotype and severity of stress. Additionally, elevated carbon dioxide levels, a key aspect of climate change, can have varying positive or negative effects on safflower growth and performance, depending on the level of salinity stress and genotype.
