The effect of extreme dehydration on photosynthetic activity of Sphagnum denticulatum cultivated genotypes from different habitats

The effect of water deficit on drought-sensitive peat mosses’ photosynthetic activities were analyzed in Sphagnum denticulatum genotypes representing two ecotypes–aquatic and terrestrial. All plants, cultivated for a long time in common garden conditions, were desiccated to a water content of less than 2% of controls and subsequently rehydrated for up to 30 days. The aquatic control plants showed shade adaptations as expressed by the F₀, F_v/F₀ and Chl a/b ratios which may reflect the conditions at the parental habitat. The ecotype- and genotype-specific responses to desiccation and rehydration were observed. Under desiccation, the photoinhibition was greater in the terrestrial plants (as demonstrated by lower F_v/F_m and Φ_PSII), in comparison with the aquatic plants. This suggests either severe damage of photo centers or better photoprotection mechanisms. Although there were no consistent differences between ecotypes across treatments, the signs of intraspecific variation in desiccation sensitiveness, which presumably arose from plasticity and local adaptation of plants to their parental environments, were detected. Genotypes and their place of origin should be taken into account in future studies.