Prehydration Mitigates Damage Accrued From Prolonged Periods Of Desiccation In Cultured Shoot Apices Of Syntrichia Ruralis

Introduction.We hypothesised that a prehydration period (exposure to humid air) should mitigate the damaging effects of short or long periods of desiccation in a desert moss, Syntrichia ruralis.Methods.Cultured uniclonal shoots of S. ruralis were dried rapidly, equilibrated at 42% relative humidity (RH), allowed to remain at this RH for 1-50 days, and either (1) prehydrated (24 h at 100% RH) then rehydrated with liquid water, or (2) rehydrated directly using liquid water without a prehydration treatment, and assessed using chlorophyll fluorescence and visual damage.Key results.At both 20 min and 24 h postrehydration, all chlorophyll fluorescence measures (F (m), F (v)/F (m), phi(PSII), qP) were higher in shoots that were prehydrated. Prehydrated S. ruralis shoots also had less visual leaf damage 7 d postrehydration. Duration-dry (DD) had an overall negative effect for all fluorescence measures on shoots immediately after rehydration, an effect that dissipated at 24 h postrehydration in three of the four fluorescence measures (F (m), F (v)/F (m), phi(PSII)). Leaf damage was not influenced by Duration-dry. Although no interaction was detected between Prehydration and Duration-dry treatments, the benefits of prehydration were accentuated based on fluorescence metrics F (v)/F (m) and phi(PSII), when shoots are exposed to longer drying periods.Conclusions.A prehydration treatment implemented just prior to hydration with liquid water significantly mitigated shoot damage accrued from a prior rapid drying event and DDs of up to 50 d at 42% RH. Based on photosynthetic efficiency, prehydration conferred greater effects at longer DDs. Experiencing humid conditions prior to rainwater mitigates damage incurred during prolonged desiccation.