Rhizosheath: Roles, Formation Processes and Investigation Methods

Climate change negatively affects crop productivity, threatening the survival of entire populations from many vulnerable hotspot regions of the world with the risk of exacerbating hunger, malnutrition and international inequality. Selecting plant species manifesting abiotic stress-tolerant adaptive traits represents a challenge towards ensuring that crops are more resistant and resilient to environmental perturbations. The rhizosheath, defined as the complex of root hair, exudates and soil that strongly adheres to plant roots, is a promising root adaptive trait in facing conditions of water and nutrient deficits, as well as acidic soil. Several beneficial ecological functions are attributed to the rhizosheath, such as enhancing water and nutrient uptake; protecting from dehydration, heat and acid stresses; and stimulating microbial activities. It has been described in several Angiosperm species, including crops grown in severe habitats. The aim of this review was to collect the relevant literature produced to date regarding rhizosheaths, focusing on (i) the various processes involved in its formation, including both physicochemical and biological ones; (ii) the evolutionary and ecological role of rhizosheaths; and (iii) the most frequently used methodologies for its investigation and characterization. The present work provides a comprehensive overview of this revolutionary root’s great agronomic importance in order to address future research aiming to fill the existing knowledge gaps and define a common and shared methodology

Lampenflora, the Alien of Show Caves: Monitoring and Treatments

Rosangela Addesso¹, Jo De Waele², Daniela Baldantoni¹ ¹Department of Chemistry and Biology “Adolfo Zambel- li”, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano (SA), Italy;²Department of Biological, Geological and Environmental Sciences, University of Bologna, Via Zamboni, 67, 40126 Bologna, Italy Caves are often subject to tourist adaptations, causing an irreversible impairment of the bio-geochemical equilibria, which are still not entirely understood, due to the scarcity of information. Between the most worrisome consequences, there is the development of photoautotrophic and mixotrophic communities, called “lampenflora”, growing because of artificial lighting. They are considered the main responsible of the surface alterations, with possible damaging effects, jeopardizing the speleothem conservation, included the still scarcely known vermiculations. This work aims to shed light on the efficacy of monthly chemical (15% H2O2 and commercial bleach) and physical (one night UV-C) growth-control treatments, as well as the triggered alteration processes, on small test surfaces covered by lampenflora, with and without vermiculations. The study, carried out in the tourist lit trail of the Pertosa-Auletta Cave (southern Italy), reports preliminary findings on the photosynthetic activities of such communities, before and after the treatments. The analysis of maximal photo-chemical yield (MINI-PAM, Walz) was performed through in situ non-destructive chlorophyll fluorescence measurements. The preliminary findings of the research show promising results, highlighting a reduced photo-synthetic activity of the lampenflora already after the first two treatments. Indeed, pre-treatment measurements on the dark-adapted surfaces, with and without vermiculations, showed Fv/Fm values between 0.766-0.713 and 0.710-0.663, respectively. After the first H2O2 and bleach treatments, the maximal PSII photochemical efficiency was similar, on average 0.024, and did not change for a month nor after the second treatment, indicating an almost complete reduction of biological activity. For the surfaces interested by UV-C treatments, no detectable effect occurred in relation to the photo-synthetic activity, suggesting the need to increase the number of such treatments to twice a month, or even weekly

Sustainable Tourism and Conservation of Underground Ecosystems through Airflow and Particle Distribution Modeling

Underground ecosystems are often of interest for the tourism industry due to their important naturalistic and cultural heritage. Since these underground ecosystems are almost completely isolated, external agents (such as human presence) can easily disrupt their chemico-physical and biological processes, which can affect, sometimes irrevocably, their natural equilibrium, placing the preservation of such sites at risk. The most sensible managers of caves, catacombs, mines, and all the accessible cultural sites are searching for methods to control these dynamics and the modeling appears to be effective in preventing scenarios of the known impacts as well as suggesting strategies for their mitigation. In this study, by employing finite element analysis by the COMSOL Multiphysics software and reproducing, in a simplified way, a section of the tourist trail of the Pertosa-Auletta Cave (Italy), for the first time we provided a fact-finding survey of the airflow and the scattering and subsequent deposition of particles transported by tourists. Taking into account discontinuities in the pathway, the simulations rebuilt the possible natural airflow line, reproducing the particle movements induced by different tourist loads, whose high numbers increase the swirling movement of air masses, promoting a higher dispersion of particles, even in the remote cave areas. Performed simulations clearly indicated both the speed and direction followed by particles, as well as deposition sites, highlighting potential hotspots of damage, and demonstrating that the employed approach can be an excellent tool for planning the management of these extraordinary ecosystems, foretelling anthropogenic impacts, and supporting managers in decision-making processes

Lampenflora growth-control: the challenge of the show caves

Show caves are subjected to tourist adaptations, often with negative consequences on the ecological equilibria of the system. Among the worst problems, photosynthetic biofilms, called “lampenflora”, can develop on surfaces due to the artificial lighting system, covering with green patinas every lit rocks, included speleothems, such as the still few known vermiculations. They implement biodeteriorations processes on surfaces, damaging them irreversibly. The aim of this study was to investigate the efficacy of lampenflora growth-control strategies, carried out monthly using chemical (15% hydrogen peroxide2 or commercial bleach) and physical (UV-C) remedies, on surfaces with and without vermiculations. The tests were performed in the tourist trail of the Pertosa-Auletta Cave (southern Italy), lit and frequented by human beings, analyzing, before and after the treatments, the chlorophyll fluorescences (MINI-PAM, Walz), an in situ non-destructive method representing a proxy of the biofilms photosynthetic activities. The results highlighted an evident reduction of the lampenflora photosynthetic activity already after the 1st treatment. Before every actions, the dark-adapted surfaces, with and without vermiculations, displayed Fv/Fm values between 0.766-0.713 and 0.710-0.663, respectively. After chemical treatments, using H2O2 or commercial bleach, the maximal PSII photochemical efficiency was close to 0, showing an almost complete reduction of the photosynthetic activity. Such values have been maintained until the 2nd treatment, in pre- and post phase. After three months without treatments due to the pandemic lockdown closure of the show cave, there was a slight recovery of lampenflora on the surfaces treated with H2O2, immediately stopped after the 3rd treatment. No effect occurred on the surfaces treated with UV-C, probably in relation to the low frequency of treatments (one night) in a month

Underground ecosystem conservation through high-resolution air monitoring

In cave ecosystems tourists represent moving sources of discontinuous disturbances, able to induce transient system responses whose knowledge is crucial in defining appropriate conservation measures. Here we propose an approach to evaluate the amplitude and scales of cave alterations based on high-resolution air monitoring, through the use of purposely developed low-cost monitoring stations and a consistent analytical framework for information retrieval based on time series analysis. In particular, monitoring stations adopt a modular structure based on physical computing platforms acquiring data through several sensors, with means of preventing humidity damages and guaranteeing their continuous operation. Data are then analyzed using wavelet periodograms and cross-periodograms to extract the scales of tourism-induced alterations. The approach has been exemplified in the Pertosa-Auletta Cave, one of the most important underground environments in Southern Italy, highlighting the development of monitoring stations and the information obtainable with the proposed analytical workflow. Here, 2 monitoring stations acquiring data for 1 year at 1′ sampling time on temperature, relative humidity, CO2, VOCs, and particulate matter were deployed in trails subjected to different levels of tourism. In terms of Pertosa-Auletta Cave air dynamics, the approach allowed estimating the temporal and spatial scales of tourism-induced alterations in the order of minutes and meters, respectively, with parameter-dependent variations. On more general terms, the approach proved reliable and effective, with its modularity and low-cost fostering its straightforward adoption in other underground ecosystems, where it can support the development of tailored management strategies

High-resolution atmospheric monitoring in cave ecosystems: dynamics, impacts and implications for management and conservation

The adoption of data-driven policies is increasingly recognized as the gold standard in managing and preserving ecosystems and relies on effective means of continuously monitoring environmental dynamics. Such an approach is crucial wherever even light anthropogenic pressures are able to exert deep alterations, like in cave ecosystems, where tourism fruition introduces moving sources of discontinuous disturbances. In this context, novel tools for high-resolution monitoring of cave atmosphere, coupling affordability and ease of construction with accuracy and adaptability to different requirements/environments, were developed. The approach pivots on low-cost and modular monitoring stations, organized into networks, providing high resolution data on several atmospheric parameters, and on an analytical workflow able to extract information on the temporal and spatial scales of tourist-induced alterations. The system can be also invaluable in shedding light on the natural dynamics of these peculiar environments, still scarcely understood, as we demonstrated in the Pertosa-Auletta Cave, one of the most important karst systems of southern Italy. In particular, the monitoring system allowed understanding the annual dynamics of temperature, relative humidity, CO2, VOC, and particulate matter size and concentration, evaluating their alterations induced by tourists and identifying the spatial and temporal scales of the latter. On the one hand, findings shed novel light on the dynamics of this peculiar system, on the other hand, the simplicity, low-cost and effectiveness of the approach make it straightforwardly applicable to other underground ecosystems, where it can support the adoption of tailored management strategies

Lampenflora, the alien of show caves: monitoring and treatments

Caves are often subject to tourist adaptations, causing an irreversible impairment of the bio-geochemical equilibria, which are still not entirely understood, due to the scarcity of information. Between the most worrisome consequences, there is the development of photoautotrophic and mixotrophic communities, called “lampenflora”, growing because of artificial lighting. They are considered the main responsible of the surface alterations, with possible damaging effects, jeopardizing the speleothem conservation, included the still scarcely known vermiculations. This work aims to shed light on the efficacy of monthly chemical (15% H2O2 and commercial bleach) and physical (one night UV-C) growth-control treatments, as well as the triggered alteration processes, on small test surfaces covered by lampenflora, with and without vermiculations. The study, carried out in the tourist lit trail of the Pertosa-Auletta Cave (southern Italy), reports preliminary findings on the photosynthetic activities of such communities, before and after the treatments. The analysis of maximal photochemical yield (MINI-PAM, Walz) was performed through in situ non-destructive chlorophyll fluorescence measurements. The preliminary findings of the research show promising results, highlighting a reduced photosynthetic activity of the lampenflora already after the first two treatments. Indeed, pre-treatment measurements on the dark-adapted surfaces, with and without vermiculations, showed Fv/Fm values between 0.766-0.713 and 0.710-0.663, respectively. After the first H2O2 and bleach treatments, the maximal PSII photochemical efficiency was similar, on average 0.024, and did not change for a month nor after the second treatment, indicating an almost complete reduction of biological activity. For the surfaces interested by UV -C treatments, no detectable effect occurred in relation to the photosynthetic activity, suggesting the need to increase the number of such treatments to twice a month, or even weekly

Cave vermiculations, life hotspots for studies of hypogean microbiology

Póster presentado en 20th Eruropean Astrobiology Network Association Conference (EANA-2021) Online.- September 7-10, (2021)Peer reviewe

Sustainable Tourism and Conservation of Underground Ecosystems through Airflow and Particle Distribution Modeling

Underground ecosystems are often of interest for the tourism industry due to their important naturalistic and cultural heritage. Since these underground ecosystems are almost completely isolated, external agents (such as human presence) can easily disrupt their chemico-physical and biological processes, which can affect, sometimes irrevocably, their natural equilibrium, placing the preservation of such sites at risk. The most sensible managers of caves, catacombs, mines, and all the accessible cultural sites are searching for methods to control these dynamics and the modeling appears to be effective in preventing scenarios of the known impacts as well as suggesting strategies for their mitigation. In this study, by employing finite element analysis by the COMSOL Multiphysics software and reproducing, in a simplified way, a section of the tourist trail of the Pertosa-Auletta Cave (Italy), for the first time we provided a fact-finding survey of the airflow and the scattering and subsequent deposition of particles transported by tourists. Taking into account discontinuities in the pathway, the simulations rebuilt the possible natural airflow line, reproducing the particle movements induced by different tourist loads, whose high numbers increase the swirling movement of air masses, promoting a higher dispersion of particles, even in the remote cave areas. Performed simulations clearly indicated both the speed and direction followed by particles, as well as deposition sites, highlighting potential hotspots of damage, and demonstrating that the employed approach can be an excellent tool for planning the management of these extraordinary ecosystems, foretelling anthropogenic impacts, and supporting managers in decision-making processes

Cave vermiculations, life hotspots for studies of hypogean microbiology

Cave microbiota plays a key role in the genesis processes of underground environments. In fact, they are involved in the biogeochemical cycles, interacting with the rock substrates through both constructive and destructive pathways and contributing to the formation of speleothemes (1), such as vermiculations, still unexplored peculiar sedimentary structures, occurring on the walls of natural or artificial caves (2). Latest researches pointed out microbial evidences supporting their biological origin (3). The goal of the work was to shed light on the geochemical and microbiological characteristics of vermiculations from Pertosa-Auletta Cave (Campania, southern Italy), contributing also to the knowledge of microbial biodiversity of such karst system. Next-generation sequencing surveys showed the occurrence of Proteobacteria (48.0%), Acidobacteria (11.6%), Actinobacteria (7.1%), Nitrospirae (5.8%), Firmicutes (4.3%), Planctomycetes (3.2%), Chloroflexi (1.9%), Gemmatimonadetes (1.1%). Numerous less-represented bacterial groups (< 1%), Archaea (0.1%), as well as a significant percentage of unclassified microorganisms (13.1%), were also detected. X-ray diffraction revealed the mainly calcitic composition of the deposits, with a low amount of quarts and clay minerals. Moreover, they exhibited a wide variations in Al, Ba, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, S, Si, Sr, Ti, V and Zn concentrations among the analyzed samples. Field emission scanning electron and confocal laser scanning microscopy supported the hypothesis of the functional microbial activity in the development of vermiculations, highlighting several dissolution shapes, but also the presence of biogenic secondary minerals and organic matter. 1. Tomczyk-Żak, K. and Zielenkiewicz, U. (2016) Geomicrobiology Journal 33:20–38. 2. Hill, C.A. and Forti, P. (1997). Cave minerals of the world. National Speleological Society II Edition 463. 3. Jones, D.S. et al. (2008) Journal of Cave and Karst Studies 70(2): 78-93