The role of peltate scales in desiccation tolerance of Pleopeltis polypodioides

Abstract

The extreme drought tolerance of the resurrection fern is in part the result of the dorsal scales that assist in water distribution and controlled desiccation. We studied the effect of peltate scales on water uptake and loss of the desiccation-tolerant epiphytic fern Pleopeltis polypodioides using optical and FTIR microscopy and staining with calcofluor, solophenyl flavine7GFE, and Ruthenium Red. We provide information on structure, property, and function of the scales by measuring water uptake and dehydration, contact angles, and metabolic activity. Peltate scales mainly contain cellulose, xylogalactans, and pectin. Water is absorbed from the center of scales, and the overlapping arrangement of scales facilitates surface spreading of water. Intact fronds hydrated fully within 5 h of imbibition of the apical pinna, without scales water uptake stopped after 1 h. Hydration rates via rhizomes followed a longer time course but also improved in the presence of scales. Fronds with and without scales lost half of their water content in 15 or 4 h, respectively. The overall metabolism of rapidly dehydrated fronds was significantly reduced compared with slowly dehydrated fronds. Thus, water management and metabolism of Pleopeltis are dependent on surface properties determined by peltate scales.

High‐resolution computed tomography reveals dynamics of desiccation and rehydration in fern petioles of a desiccation‐tolerant fern

“…Since vegetative DT has evolved several times in vascular plants (Gaff & Oliver, ), other DT species may show contrasting mechanisms of whole‐plant resurrection. For instance, Pleopeltis polypodioides has been shown to resurrect via specialized scales on the leaf surface (John & Hasenstein, ). Consequently, stipe anatomical traits may be less critical for resurrection in this species, as foliar water uptake likely plays a more significant role in the resurrection process.…”

Peltate trichomes on biogenic silvery leaves of Elaeagnus umbellata

“…Trichomes are commonly regarded to reduce the diffusion rate of water vapor through the stomata by interfering with air flow on the leaf surface with respect to water conservation (John & Hasenstein, ). Given the pioneer species characteristics of E. umbellata (Yates, Levia, & Williams, ), it is possible that the predominant peltate trichomes on the abaxial leaf surface may partially confer the shrub drought‐resistance under arid conditions.…”

Desiccation Mitigates Heat Stress in the Resurrection Fern, Pleopeltis polypodioides

“…Pleopeltis polypodioides (aka resurrection fern) can tolerate loss of 95% of cellular water content and regain full metabolic activities within a few hours of rehydration (Pessin, 1924;Stuart, 1968;John and Hasenstein, 2017). In response to dehydration, the ventral surface curls inward and the dorsal surface, covered with peltate scales, remains exposed (Pessin, 1924).…”

“…Such folding mechanisms, also demonstrated by other resurrection plants, are thought to be a defensive mechanism against photooxidation (Farrant et al, 1999;Helseth and Fischer, 2005). Although there is plenty of information on morphological changes of plants in response to heat and desiccation stress, adaptations of ferns to desiccation (Pessin, 1924;Stuart, 1968;Helseth and Fischer, 2005;John and Hasenstein, 2017), and biochemical response to drought (Maslenkova and Homann, 2000;Georgieva and Maslenkova, 2001;Layton et al, 2010;John and Hasenstein, 2018) are limited. In addition, the response of Pleopeltis to heat has not been investigated.…”