Physiological Benefits of Stem Curling for Resurrection Plants in the Field

Abstract

The stems of the resurrection plant Selaginella lepidophylla, a poikilohydrous desert pteridophyte, curl dramatically as the plants dry and uncurl when rewetted. We tested the hypothesis that stem curling is a morphological feature that may serve to limit bright-light and/or thermal damage in resurrection plants with a field experiment at a Chihuahuan desert site in west Texas. Experimental plants were irrigated for 3d and then permitted to dry. The plants were either allowed to curl normally or mechanically restrained to prevent curling and either shaded (l 0% of ambient irradiance) or left fully exposed during desiccation. Nine days after complete desiccation, the plants were harvested and returned to the laboratory. When rehydrated, plants that had been unshaded and restrained from curling during field desiccation had significantly lower photosystem II electron transport rates, higher intrinsic chlorophyll fluorescence (F0 ) yields, lower variable to maximum chlorophyll fluorescence (F/ F m) yield ratios, lower chlorophyll contents, and both lower whole-plant photosynthetic quantum efficiencies and light-saturated C02 assimilation rates relative to plants from the other desiccation treatments. The results of both low-irradiance and high-irradiance hydrations in the laboratory suggest that the curling during desiccation and the uncurling during rehydration of S. lepidophylla in its natural habitat serves to protect the plant from damage due to high irradiance, high temperature, or perhaps a synergistic combination of the two. This protection permits the rapid recovery of photosynthetic competence when next the plants are wetted, thereby helping to maximize net carbon balance over time.

Desiccation tolerance in the vegetative tissues of the fern Mohria caffrorum is seasonally regulated

“…Chlorophyll shading and masking is characteristic of homoiochlorophyllous angiosperm resurrection plants (Farrant et al. , 2003; Sherwin and Farrant, 1998), and frond curling has also been noted in the DT fern Polypodium polypodioides and fern ally Selaginella lepidophylla (Helseth and Fischer, 2005; Lebkuecher and Eickmeier, 1993), features that are thought to minimize photosynthetic ROS production during drying (Farrant, 2000, 2007; Oliver et al. , 1998; Smirnoff, 1993; Vicre et al.…”

“…Although it is well documented that there are several species of pteridophytes with vegetative DT (Alpert and Oliver, 2002;Gaff, 1977;Helseth and Fischer, 2005;Lebkuecher and Eickmeier, 1993;Muslin and Homann, 1992;Pessin, 1924;Reynolds and Bewley, 1993), little has been reported on the mechanisms used to survive cellular desiccation. It has been inferred by Oliver et al (1998) that as the rate of drying in pteridophytes is slow, they are likely to, like angiosperms, rely more on the de novo accumulation of protection during drying than on the constitutive protection coupled with rehydration-associated repair that is characteristic of bryophytes.…”

Leaf rosette closure in the alpine rock species Saxifraga paniculata Mill.: significance for survival of drought and heat under high irradiation

“…The potential role of leaf movements in avoiding photoinhibition has been discussed for a number of species (e.g. Hirata et al 1983 ; Ludlow & Björkman 1984; Ryel & Beyschlag 1995; stem curling Lebkuecher & Eickmeier 1993). Photoinhibition can reduce carbon gain and thus affect establishment of certain species in special environments ( Ball, Hodges & Laughlin 1991).…”

Poikilohydry and homoihydry: antithesis or spectrum of possibilities?

“…Thus there is plenty of evidence of responses of antioxidants and antioxidant enzyme systems to drying and rehydration, but it is hard to discern any consistent general pattern. Lebkuecher & Eickmeier (1991, 1993) and Muslin & Homann (1992) showed that leaf curling in dry Selaginella lepidophylla and Polypodium polypodioides brings clear benefits in limiting photodamage during rehydration in bright light, but their results do not suggest any fundamental differences from nonDT plants. Over all, the evidence suggests that DT plants generally deal with the potential hazards of oxidative damage during the drying–re‐wetting cycle by anticipating the problem at source rather than by invoking extravagantly high activity of antioxidant enzymes or antioxidants after the event.…”