• Energy Research

There are great concerns for the accumulation in the environment of small dimension plastics, such as micro- and nanoplastics. Due to their small size, which facilitates their uptake by organisms, nanoplastics are of particular concern. The toxic effects of nanoplastics on plants are already reported in the literature, however nothing is known, to date, about the possible effects of climate change, in particular of increasing temperatures, on their toxicity for plants. To address this issue, plants of the water fern Azolla filiculoides were grown at optimal (25 °C) or high (35 °C) temperature, with or without polystyrene nanoplastics, and the effects of these stressors were assessed using a multidisciplinary approach. Green fluorescent polystyrene nanoplastics were used to track their possible uptake by A. filiculoides. The development and physiology of our model plant was adversely affected by both nanoplastics and high temperatures. Overall, histological, morphological, and photosynthetic parameters worsened under co-treatment, in accordance with the increased uptake of nanoplastics under higher temperature, as observed by fluorescence images. Based on our findings, the concern regarding the potential for increased toxicity of pollutants, specifically nanoplastics, at high temperatures is well-founded and warrants attention as a potential negative consequence of climate change. Additionally, there is cause for concern regarding the increase in nanoplastic uptake at high temperatures, particularly if this phenomenon extends to food and feed crops, which could lead to greater entry into the food chain.

<p><em>Jatropha curcas </em>L. and <em>Jatropha macrocarpa </em>Griseb. (Euphorbiaceae) are perennial species adapted to marginal conditions not suitable for agriculture, and have been recently exploited for oil and biodiesel production<strong>. </strong>The anatomy of different organs in members of this family exhibits a wide range of variations. However, knowledge of anatomical features is still incomplete. The aim of the present work was to analyze the anatomical structure of stem, leaf and root of <em>J. curcas </em>and <em>J. macrocarpa </em>seedling cultivated in a greenhouse. Fixed samples were properly treated using triple stain hematoxylin, safranin and fast green. Primary roots were diarch and triarch in <em>J. curcas</em>, whereas in <em>J. macrocarpa </em>were diarch and the cortex showed parenchyma cells, larger in <em>J. macrocarpa</em> than <em>J. curcas</em>. Stem cortex was thicker in <em>J. macrocarpa</em> than in <em>J. curcas</em>.<em> </em>Both species had parenchyma cells with cystolith, chloroplasts, laticifers and starch granules, these being more abundant in <em>J. macrocarpa</em>. Leaves were characterized by dorsoventral anatomy, with the epiderm showing amphistomatic condition with high stomata density at the lower surface. Both <em>Jatropha </em>species had paracytic stomata. Druses and non-articulated branched laticifers were recorded in the mesophyll. Some of the different anatomical features of <em>J. curcas </em>and <em>J. macrocarpa</em> could explain the different tolerance to abiotic stress.</p>

Cistus salviifolius is able to colonise one of the most extreme active geothermal alteration fields in terms of both soil acidity and hot temperatures. The analyses of morpho-functional and physiological characters, investigated in leaves of plants growing around fumaroles (G leaves) and in leaves developed by the same plants after transfer into growth chamber under controlled conditions (C leaves) evidenced the main adaptive traits developed by this pioneer plant in a stressful environment. These traits involved leaf shape and thickness, mesophyll compactness, stomatal and trichome densities, chloroplast size. Changes of functional and physiological traits concerned dry matter content, peroxide and lipid peroxidation, leaf area, relative water and pigment contents. A higher reducing power and antioxidant enzymatic activity were typical of G leaves. Though the high levels of stress parameters, G leaves showed stress-induced specific morphogenic and physiological responses putatively involved in their surviving in active geothermal habitats.

The research interest of our group is the impact of climate changes on natural plant species of Mediterranean environments. Global changes potentially expose plants to novel environmental conditions that may be outside of their physiological limits and disrupt evolutionary patterns, while also influencing the interactions between plants and whole ecosystems. Understanding the physiological mechanisms of resistance to stress is fundamental to improve predictions of the effects of climate change, because they may be a key indicator of plant resiliency (or lack thereof) in future environments. Our attention is focused also on invasive plant species, whose competitive ability might be altered by climate changes. Mediterranean coasts are rich of biodiversity, but are intensively exploited for recreational and economic activities. This environment is particularly vulnerable to climate changes, thus urging us to investigate it in depth, in search of clues that may help to foresee and prevent damages to these ecosystems. Markers of plant stress may serve this purpose, therefore our ecophysiological investigations aim at applying basic research in the conservation of natural ecosystems and in the preservation of supply of goods and services for human activities. A few case studies are described to outline the research work of our group.