Impact of varying diurnal temperature ranges on regulation of multiple physiological traits of a drought-tolerant moss (Grimmia pilifera).

Mosses that usually exist as gametophytes lack true roots, stems, and leaves, and their physiological activity is highly sensitive to environmental changes. The increase of diurnal temperature range (DTR) is one of the important characteristics of global climate change, but it is still unclear how mosses respond to the change of DTR. The typical drought-tolerant and saxicolous moss Grimmia pilifera was used as the research subject, two DTR treatments were set up: 20/10 ℃ (day/night; as natural habitat temperature) and 30/10 ℃ (day/night; as increased DTR). After homogenized cultivation, three dehydration-rehydration cycles and physiological measurements were conducted on days 7, 14, and 21 to investigate the comprehensive response of mosses to change in DTR over time. The results showed that under different diurnal temperature range (DTR) treatments, the chlorophyll fluorescence parameters of Grimmia pilifera exhibited marked responses to the dehydration-rehydration process, characterized by inhibited PSII activity, enhanced energy dissipation, and restricted electron transport during dehydration, with partial recovery of these parameters upon rehydration. Compared to the 20/10°C treatment, the 30/10°C treatment resulted in more pronounced inhibition during dehydration, but also demonstrated a stronger recovery capacity after rehydration. Water content (WC) declined over time, and its recovery after rehydration was significantly lower under 30/10°C than 20/10°C. Overall, the MDA content at both 14 and 21 days was significantly lower than the initial level, with a more substantial decrease observed under the 30/10°C treatment on day 21. The 30/10°C treatment exhibited lower activity of antioxidant enzymes (primarily CAT), and showed higher levels of osmotic adjustment substances (PRO, SP). The plant trait network analysis revealed that the core traits on days 7, 14, and 21 under the 20/10 ℃ treatment were WC, PI abs, and ETo/RC, respectively; while under the 30/10 ℃ treatment, the core traits were PI abs, SP, and PRO content, respectively. The stability of trait network structure was higher under the 20/10 ℃ treatment than under 30/10 ℃. Analysis of pooled data showed that the core traits under both treatments were photosynthetic parameters (Fv/Fo under 20/10 ℃ and PI abs under 30/10 ℃), indicating that G. pilifera exhibited differential changes in trait network structure and core traits over time under varying DTRs, but overall relied on coordinated regulation of the photosynthetic system to cope with environmental stress. These findings provide new physiological and ecological insights into how mosses respond to global climate change.