Desiccation tolerance in Pleurostima purpurea (Velloziaceae)

Abstract

Previous works suggested that Pleurostima purpurea (Velloziaceae-Barbacenioideae) shows a remarkable capacity to endure desiccation of its vegetative tissues. P. purpurea occurs in monocotyledons mats on soil islands in the Pão de Açucar (Sugar Loaf) one of the most recognizable rock outcrops of the world, in Rio de Janeiro, southeastern Brazil. Mats of P. purpurea occur in cliffs by the sea some meters above the tidal zone. Although living in rock outcrops almost devoid of any soil cover, P. purpurea seems to occur preferably on less exposed rock faces and slightly shady sites. Usually, less extreme adaptations to drought would be expected in plants with the habitat preference of P. purpurea. Relying on this observation, we argue if a combination of different strategies of dealing with low water availability can be found in P. purpurea as on other desiccation tolerant angiosperms. This study aims to examine the occurrence of desiccation tolerant behavior in P. purpurea together with the expression of drought avoidance mechanisms during dehydration progression. For this, it was analyzed the gas exchanges, leaf pigments and relative leaf water content during desiccation and rehydration of cultivated mature individuals. P. purpurea behaved like typical drought avoiders under moderated drought condition with stomatal closure occurring around a relative leaf water content up to 90%. During this process, it was observed a delay in the leaf relative water content (RWC leaf ) decrease comparing to the plant-soil relative water content (RWC plant-soil ). As soil dehydration worsened, gas exchanges restrictions progressed until a lack of activity which characterizes anabiosis. The loss of chlorophyll occurs before the end of total dehydration, characterizing the presence of poikilochlorophylly. The chlorophyll degradation follows the RWC leaf decrease, which achieved the minimum average value of 17% without incurring in leaf abscission. The chlorophyll re-synthesis seems to start well after the full rehydration of the leaf. During all of this process, carotenoid content remained stable. These results are coherent with a combination of drought avoidance and desiccation tolerance in P. purpurea which seems to be coherent with the amplitude of water availability in the rock outcrop habitat where it occurs, suggesting that the periods of water availability are sufficiently long for the success of the costly desiccation tolerant behavior but too short to make a typical drought avoider species win the competition for exploring the rock outcrop substrate where P. purpurea occurs.

Leaf metabolite profile of the Brazilian resurrection plant Barbacenia purpurea Hook. (Velloziaceae) shows two time-dependent responses during desiccation and recovering

“…This behavior evidences the poikilochlorophyllous strategy, which is a characteristic of monocots (Farrant, 2000; Porembski and Barthlott, 2000). As seen in a previous study (Aidar et al, 2010), B. purpurea degrades the components of the photosynthetic apparatus only at the final stage of drying. The degradation of chlorophylls possibly occurs to prevent excessive absorption of UV radiation, as reported for Xerophyta viscosa (Sherwin and Farrant, 1998).…”

“…This is a common response in resurrection plants and has been related to the reduction of transpiration surface, facilitating temperature control and limiting the damage caused by radiation incidence (Sherwin and Farrant, 1998; Dinakar et al, 2012). The transpiration decrease due to the reduction of the stomatal conductance was observed in plants of B. pupurea (= Pleurostima purpurea ) upon water deficit (Aidar et al, 2010). Metabolites such as fumarate have been reported as important stomatal controlers (Nunes-Nesi et al, 2007), avoiding water loss and gas exchange.…”

Editorial: special issue GROW “plant desiccation stress”

“…Koster et al (2010) quantify the extent of dehydration tolerance in the moss Physcomitrella patens, a species that is gaining importance as a model organism for functional genomics studies of bryophyte responses to abiotic stresses. Aidar et al (2010) confirm that Pleruostima purpruea is indeed a resurrection plant that displays poikilochlorophyllous protection mechanisms to minimise oxidative stresses associated with photosynthesis during desiccation. Proctor (2010) utilizes chlorophyll-fluorescence parameters to compare and quantify recovery responses in a range of bryophytes and pteridophytes and proposes that this tool can give insight into factors influencing recovery time and rate.…”

“…Typically such studies pose specific research questions and are conducted using discipline specific approaches on a single species, but often reflect some common questions and strategies associated with research into desiccation tolerance. Papers within this issue report on stresses associated with water deficit, such as the mechanical stress of plasmolysis (Koster et al 2010), oxidative stresses, including those associated with light (Aidar et al 2010;Proctor 2010;Kamies et al 2010;Colville and Kranner 2010) and the protective responses generated in response to those stresses, or take a more global approach of searching for genes and gene products up regulated in response to stress (Abdalla et al 2010). In addition to furthering our understanding of stresses and associated protection these works add important information to the field.…”

The Resurrection Plant Tripogon Spicatus (Poaceae) Harbors a Diversity of Plant Growth Promoting Bacteria in Northeastern Brazilian Caatinga

“…These species are able to maintain viable quiescent vegetative tissues throughout long desiccation periods due to the activation of several mechanisms, including strong light protection of leaf tissues (Aidar et al, 2010(Aidar et al, , 2014, synthesis of osmoprotectants, membrane and protein stabilizers (Morse et al, 2011). tripogon spicatus Ekman Nees is a resurrection grass naturally occurring in the Americas from the south of Texas (USA) to the Patagonia Desert (Argentina).…”