https://bsr.ujiroft.ac.ir/ Biospecies Research en daily 1 Sat, 01 Aug 2026 00:00:00 +0330 Sat, 01 Aug 2026 00:00:00 +0330 https://bsr.ujiroft.ac.ir/article_247661.html Elevated ambient temperatures adversely affect livestock production. Among domestic animals, sheep in southern Iran experience heat stress for seven months annually based on the Temperature-Humidity Index (THI), sheep in this region experience heat stress conditions for seven months of the year. Understanding the endocrine mechanisms that regulate metabolic homeostasis may provide insights into how sheep cope with such stress. Thyroid hormones—namely triiodothyronine (T3) and thyroxine (T4)—play fundamental roles in metabolic processes and thermoregulation. In this study, plasma levels of T3 and T4 were measured in Kermani sheep during winter and summer. Both hormones were significantly lower in summer than in winter (P < 0.007). However, the calculated T3/T4 ratio was significantly higher in summer (P < 0.001), indicating a 15-fold increase in the conversion of T4 to T3 compared to winter. Although overall thyroid hormone production declined during summer, Although overall thyroid hormone concentrations declined during summer, the increased T3/T4 ratio suggests possible alterations in peripheral thyroid hormone metabolism and conversion, which may contribute to the adaptive response to high ambient temperatures. Further studies measuring rT3 levels and deiodinase activity are required to confirm the underlying mechanisms. In conclusion, seasonal modulation of thyroid hormone dynamics represents a key thermoregulatory strategy in Kermani sheep. https://bsr.ujiroft.ac.ir/article_251922.html Drought is the main abiotic stress limiting safflower production in semi-arid regions, with flavonoid and anthocyanin pathways playing a key role in antioxidant defense. A two-year field experiment in Arak, Iran, evaluated 38 safflower genotypes under full irrigation and terminal drought stress, measuring total flavonoid and anthocyanin contents. Drought increased average flavonoids by 6.3% (from 0.1395 to 0.1483 mg QE g⁻¹ DW) and anthocyanins by 8.1% (from 0.00382 to 0.00413 mg g⁻¹ DW). A three-way ANOVA showed significant effects of irrigation and year on both traits, with year accounting for 62.8% of anthocyanin variance, while genotype effects were not significant (p = 0.953 and p = 0.496), indicating high residual variability (75.8% and 23.2%). Using eight drought-tolerance indices, Variety 31 ranked first for flavonoid stability (STI = 1.311), and Variety 14 ranked first for anthocyanin stability (STI = 1.952). Variety 14 was the only genotype among the top five for both traits. The correlation between flavonoid and anthocyanin contents was weak and non-significant (r = −0.06, p = 0.187), suggesting independent regulation of these two phenylpropanoid branches. These results introduce Variety 14 as a promising multi-trait parent for drought-resilience breeding and highlight that interannual climatic variation, rather than genotype, is the primary factor influencing anthocyanin accumulation in safflower petals. https://bsr.ujiroft.ac.ir/article_251924.html This study investigated the growth and physiological response in medicinal plant Carum copticum exposed to zinc oxide nanoparticles (ZnO-NPs). Treatments of 0.1, 0.2, 1, 5 and 25µM of ZnO-NPs compared with 0.2 µM ZnSO4 (control; Zn form in Johnson solution) were applied in culture media under hydroponic conditions. The plants shoot/root length, and water content, H2O2, anthocyanin and activity POD enzyme were measured. The root length was more sensitive to ZnO-NPs than shoot length. The 0.2 and 1 µM NPs increased plant fresh weight by 96.8 and 115.2%, respectively. The shoot and root water content increased at 0.1-25 µM NPs treatments by 40-51% and 26-34% compared to the control group, respectively. The increase in POD enzyme was accompanied by increased length and fresh weight and anthocyanin contents under ZnO-NPs. The 25 µM ZnO NPs (high level) resulted in 36% shoot length, 44% root length, 38% plant fresh weight and 27% anthocyanin decline, while increased 40% shoot water content, 26% root water content, 17% H2O2 and 69% POD activity compared with control. Overall, 25 μM ZnO-NPs treatment induced higher damages to the growth parameters due to H2O2 increase (oxidative stress) and the failure of the enzymatic and non-enzymatic mechanisms (anthocyanin and POD) to cope with the H2O2 enhancement induced by ZnO-NPs.