Physiological and transcriptomic analysis reveal responses of two different phenotypes of Dendrobium officinale to...

As a consequence of global climate warming, Dendrobium officinale (D. officinale) has increasingly been subjected to high temperature and drought stress, severely impairing its growth, development, yield, and quality. Most existing studies addressing the effects of abiotic stresses, such as elevated temperatures and water deficiency, on D. officinale have primarily concentrated on individual stressors. However, plant responses to multiple concurrent stresses are inherently complex, with varying combinations of stress factors potentially eliciting synergistic, overlapping, or antagonistic effects. Therefore, the additive impact of different stress types cannot be presumed, and plant responses under combined stress conditions cannot be fully elucidated through single-stress models. In the present study, two phenotypically distinct D. officinale germplasm resources, XL1 and XL2, were employed as experimental materials. A natural scenario of water deficit in the substrate, without replenishment, under high temperature and drought conditions was simulated. Four groups were established: control (CK), high temperature stress (H), drought stress (D), and combined high temperature and drought stress (HD). Morphological and physiological-biochemical parameters were assessed, alongside polysaccharide content determination and transcriptomic sequencing, to evaluate drought resistance and heat tolerance. The findings revealed marked differences in the physiological and biochemical traits of the two D. officinale germplasms under the respective stress conditions, particularly in morphology, antioxidative capacity, polysaccharide accumulation, and gene expression profiles. XL2 demonstrated superior resilience, whereas XL1 exhibited heightened sensitivity to combined stress. At the molecular level, the dual-stress condition markedly induced the upregulation of glycosyltransferase genes in D. officinale, thereby contributing to enhanced stress resistance.