Ferns must use water efficiently to survive in dry climates. Desiccation tolerance is one strategy by which ferns survive extreme drought. Resurrection ferns tolerate long summer drought by completely desiccating and ceasing metabolism for several months. In contrast to bryophytes and other non-vascular plants, ferns face the challenge of resurrecting complex tissues. The plants’ organs have unequal access to water; the roots and rhizome are buried in the soaked soil while the leaves are subject to variable wetness and humidity. Thus, hydraulic transport may be required to resurrect distal tissues. In this study, we teased apart the mechanisms of resurrection in two desiccation-tolerant vascular fern species, Pellaea andromedifolia and Pentagramma triangularis. These species are common in the southern California chaparral. We hypothesized that root water contributes more than leaf water to the resurrection response. We further hypothesized that positive root pressure (and not merely capillary rise) is the primary driver of resurrection in vascular ferns. We used a combination of lab and field experiments to elucidate the roles of root wetting, leaf wetting, and positive root pressure in the resurrection process.
Results/Conclusions
Our results showed that root wetting resurrected all parts of the plant, whereas leaf wetting only resurrected the leaves. Root pressure was significantly greater in the root wetting experiment than in the leaf wetting experiment. We subsequently compared the resurrection responses of cut fronds to 30 kPa and 0 kPa of water pressure applied to the cut end of the stipe. Our results indicate that added pressure improves the resurrection response in the leaves of P. triangularis and in the distal leaves of P. andromedifolia. Therefore, we conclude that positive root pressure is likely responsible for the majority of the resurrection response observed in the field following rainfall. These results may shed light on the importance of vascular function to the success of desiccation-tolerant ferns growing in deserts and mediterranean-type climates.