This study investigates the photosynthetic activity of bryobiotines, the oldest nonvascular plants of the subkingdom Bryobiotina, which represents the gametophytic lineage in land plant evolution. Both the acrocarpous moss Dicranum scoparium and the pleurocarpous moss Hylocomium splendens display a continuous gradient of senescence, allowing their shoots to be conventionally divided into distinct layers. These mosses can survive extended periods of storage in a desiccated state. We demonstrate that the photosynthetic parameters of different shoot layers reliably reflect their physiological state, including during the long-term storage. Analysis of photosynthetic indices shows that the rehydrated supertop layer of H. splendens and the top layer of D. scoparium exhibit high levels of viability after long-term storage in dry and cold conditions. Moreover, D. scoparium is resistant to high temperature (45°C) under constant humidity and to rapid dehydration over silica gel. Restoration of photosynthetic parameters following high temperature treatment suggests that among bryobiotines resistance increases in the order: Marchantia sp. < Anthoceros natalensis < D. scoparium. These findings establish that the photosynthetic apparatus of bryobiotines is resistant to a range of stress factors, including both those encountered in natural environments (dehydration and rehydration) and those that are extreme for plant survival, such as rehydration after prolonged desiccation and exposure to high temperatures under constant humidity. Photosynthetic activity serves as a convenient tool for assessing the physiological resilience of bryobiotines under abiotic stress. It provides insights into plant adaptation or mortality and enables the identification of optimal time points for subsequent transcriptomic and metabolomic analyses to elucidate the molecular mechanisms of stress responses.
Chasov et al. (Thu,) studied this question.