Aims

Highland barley often encounters simultaneous drought conditions and ultraviolet-B (UV-B) radiation exposure. Although antioxidant responses are well studied, the interaction between nutrient absorption and hormonal regulation under these combined stresses is less understood. This research explores the physiological and molecular processes underlying these cross-stress interactions.

Methods

This study examined the effects of various conditions on qingke, including MD (moderate drought; 50% field capacity), SD (severe drought; 30% field capacity), LUVB (low UV-B; 5–6 kJ m−2 d−1), radiation HUVB (high UV-B; 14–15 kJ m−2 d−1), and their combinations (MD-LUVB, MD-HUVB, SD-LUVB, SD-HUVB).

Results

Combined stresses exhibited significant drought × UV-B interactions for most traits (p < 0.05). SD-LUVB enhanced root length by 33.5% and root surface area by 28.7%, but reduced root volume (p < 0.05). The most striking improvement was observed under MD-HUVB, which increased stem Zn by 266% and stem N by 94% over CK (p < 0.05). Water use efficiency peaked under SD-HUVB (104%, p < 0.05), while nutrient use efficiency was highest under LUVB and MD-HUVB. Hormonal profiling under SD-LUVB showed significant enhancement in jasmonic acid (242%) and abscisic acid (652%), alongside changes in ethylene, gibberellin, auxin, and cytokinin. Simultaneously, combined stresses further elevated antioxidant defenses (SOD, POD, CAT) and reduced H2O2 and MDA levels, though with complex interaction patterns.

Conclusions

Drought modulates hormonal and nutritional status while UV-B reinforces antioxidant capacity. However, the effects are highly dependent on the specific combination of stresses and tissue type. Together, these pathways interactively enhance highland barley resilience, providing a template for crop adaptation in high-altitude environments.