Effects of Drought and Biochar Treatments on Some Morphological and Physiological Parameters in Turkish Hazelnut Seedlings

This study investigates the responses of 3-year-old Turkish hazelnut (Corylus colurna) seedlings to drought stress and biochar treatments, focusing on critical morphological and physiological parameters. Hazelnut, an important agricultural crop, is increasingly affected by drought due to global climate change. To mitigate these effects, biochar and the adoption of deep-rooted hazelnut systems have gained attention. The study exposed seedlings to varying levels of irrigation and biochar treatments. Results show that drought stress significantly reduced relative height growth (RHG) and relative diameter growth (RDG), while biochar had no effect on RHG and negatively impacted RDG. Decreased irrigation consistently lowered both RHG and RDG. Physiological assessments, including leaf gas exchange parameters (E, gs, Anet, WUE, iWUE, Ci/Ca) and relative water content (RWC), revealed that drought influenced these variables, whereas biochar showed no significant effect. Drought-stressed seedlings exhibited lower net photosynthesis (Anet) and stomatal conductance (gs), with no notable differences in other photosynthesis-related parameters. Chlorophyll and carotene levels also decreased under low irrigation; higher biochar doses exacerbated these reductions. Overall, the study underscores the paramount importance of water availability in hazelnut cultivation, as it had a more pronounced impact on hazelnut morphology and physiology than biochar, though the limited study duration and surface biochar treatment may have influenced these results.