Exogenous trehalose confers high temperature stress tolerance to herbaceous peony by enhancing antioxidant systems, activating photosynthesis, and protecting cell structure.

Herbaceous peony (Paeonia lactiflora Pall.) is an excellent ornamental plant, which is usually stressed by summer high temperatures, but little is known about its relevant measures. In this study, the effects of trehalose on alleviating high temperature-induced damage in P. lactiflora were examined. High temperature stress in P. lactiflora increased production of reactive oxygen species (ROS), including superoxide anion free radical (O₂^·-) and hydrogen peroxide (H₂O₂), enhanced both malondialdehyde (MDA) content and relative electrical conductivity (REC), decreased superoxide dismutase (SOD) activity, increased catalase (CAT) activity, inhibited photosynthesis, and destroyed cell structure. However, exogenous trehalose effectively alleviated its high temperature-induced damage. Trehalose decreased O₂^·- and H₂O₂ accumulation, MDA content, and REC, increased the activities of antioxidant enzymes, enhanced photosynthesis, improved cell structure, and made chloroplasts rounder. Additionally, trehalose induced high temperature-tolerant-related gene expressions to different degrees. These results indicated that trehalose decreased the deleterious effect of high temperature stress on P. lactiflora growth by enhancing antioxidant systems, activating photosynthesis, and protecting cell structure. These findings indicate the potential application of trehalose for managing high temperatures in P. lactiflora cultivation.