Syntrichia norvegica shoots exhibit a complex inducible response to desiccation: separating the effects of rate of drying and water content

Plants in the moss genus Syntrichia are considered to have constitutive desiccation tolerance (DT), as in, able to tolerate a rapid drying event without incurring significant damage upon rehydration. However, few researchers have considered the separate effects of rate of drying and water content, and incorporated fully dehardened (to DT) plants in the experiments. Plants of Syntrichia norvegica F. Weber were cultured under conditions of suprasaturation, and adult shoots were exposed to a range of drying rates and equilibrating relative humidities (RHs), rehydrated, and assessed for chlorophyll fluorescence and regeneration potential. Adult shoots exhibited severe damage across all drying rates when equilibrated at RHs <30%. However, an inducible response to desiccation was present across all water contents as the rate of drying was extended from 0 to 4 d. The least desiccation damage occurred at longer drying times and higher water contents (8 d at 75% RH). A constitutive phenotype for DT was not strictly evident in S. norvegica. Rather, we observed an incomplete pattern of environmentally inducible DT, coupled with heavy shoot damage at lower water contents. Rate of drying and equilibrating RH clearly interact in producing the pattern and strategy of DT for this species.