Contrasting Photochemical Stability and Oxidative Injury Shape Drought Responses in Ferns and Mosses

Area of Science:

• Plant physiology
• Ecology
• Evolutionary biology

Background:

• Drought poses a significant threat to terrestrial vegetation globally.
• Existing research on plant drought responses disproportionately focuses on seed plants.
• Ferns and mosses, as early-diverging land plants with distinct hydration strategies, offer a valuable comparative model.

Purpose of the Study:

• To compare the drought response strategies of ferns and mosses.
• To investigate differences in physiological performance, photoprotection, and oxidative stress between ferns and mosses under drought.
• To identify factors influencing drought sensitivity within fern species.

Main Methods:

• Compiled data from 46 drought experiments involving 35 fern and 41 moss species.
• Analyzed paired observations on water status, photosynthesis, chlorophyll fluorescence, oxidative stress, osmotic adjustment, abscisic acid, and growth.
• Compared physiological and biochemical responses between ferns and mosses.

Main Results:

• Both ferns and mosses showed reduced physiological performance under drought, with mosses exhibiting a greater mean decline.
• Ferns maintained stable maximum quantum yield and increased nonphotochemical quenching, indicating effective photoprotective regulation.
• Mosses displayed coordinated declines in photosystem II (PSII) efficiency and increased oxidative damage, suggesting direct PSII impairment and greater vulnerability.

Conclusions:

• Ferns largely maintain photochemical stability through photoregulation during drought, while mosses are more prone to PSII impairment and oxidative injury.
• Drought sensitivity in ferns is linked to specific life forms (e.g., epiphytic) and traits (e.g., specific leaf area).
• Mosses exhibit more rapid physiological decline and growth suppression under drought, highlighting their vulnerability in intensifying drought conditions.