StreeTLAMP | New streetlamp solution to reduce the impact of urban light pollution on tree and lichen species
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Scientific Referent
Working group
Antonella Gori, Francesco Ferrini, Sara Beltrami
Project partners
CNR (Istituto per la Protezione Sostenibile delle Piante)
Università di Pisa (Dipartimento di Scienze Agrarie, Alimentari e Agro-ambientali)
Main objectives
- To study the effective influences on tree and lichen phenology
- To detect the physiological and biochemical alterations in trees and lichens due to streetlamp illumination
- To understand the underlying physiological mechanism linked to the streetlamp illumination disturbance on trees and lichens
- To define the extent of physiological alterations triggered by streetlamp illumination
- To provide a new less impacting LED lamp (enriched in green and orange wavebands) realized ad-hoc for the present project
Abstract
From the middle of the nineteenth century, the use of nocturnal artificial lighting and the introduction of streetlamps in our cities have undoubtedly interfered with the natural light regulating the circadian rhythms of living organisms, including animals and land plants, the so-called light pollution.
In our cities, the new type of streetlamp illumination (SI) that uses light-emitting diode (LED) technology is replacing the old lamps. Generally, LED lamps used for SI, with two main types of chromatic variation (cold white or warm white), are richer in blue light with respect to the classic sodium lamps. This characteristic can interfere with plant cryptochromes that, together with phytochromes, sense and regulate the plant responses to environmental stimuli, thus influencing vegetative growth, germination timing, flowering, bud opening and dormancy, and leaf senescence. For example, SI may result in bud burst in several tree species due to the anticipation of bud break during unfavourable periods. Another effect is the delayed leaf senescence which is reported for some deciduous tree species such as maple, poplar, plane and sycamore growing in presence of SI.
Besides the above-mentioned reasons, there is also a complete lack of knowledge about the possible effects of SI on lichens in urban environments and on the eventual implications for their use as biomonitors of air pollution. Lichens, symbiotic associations between algal (photobiont) and fungal (mycobiont) partners, are indeed among the most widely employed biomonitors in the terrestrial environment. These organisms have the ability to promptly react, respond or adapt to environmental fluctuations, (including light irradiance) either as an individual or as a community. Therefore, it is conceivable that light interference could also influence their performances and, hence, their monitoring capabilities.
The large scale and rapid adoption of LED technology in our cities have raised an urgent need to deepen our knowledge on the potential threats for trees and lichens grown under light-polluted environments and find less impacting solutions. The StreeTLAMP project, using a multidisciplinary approach that includes arboriculture, plant physiology and biochemistry skills, is designed to provide new pieces of evidence about the influence of different LED streetlamps commonly employed in the urban environment (i.e. cold and warm white) and a new type of LED with a green/orange-enriched spectrum, developed ad-hoc for the project, on tree and lichen morpho-metric, physiological and biochemical responses.
From an applicative point of view, the results provided by StreeTLAMP will assist the stakeholders in the selection of the less impacting SI on tree and lichen performances. In addition, species-specific responses of the different trees will provide new information for the selection of the most adapted species to urban nocturnal illumination.
Project actions (in bold those coordinated by DAGRI-UNIFI)
The project activities will be organized in 4 working packages (WPs), each of them subdivided in tasks as follows:
WP1 – Effect of streetlamp illumination (SI) on tree performances
The WP will deal with the evaluation of the effect of three different streetlamps (warm, cold, green-based LED with a characterized light spectrum) on the morpho-anatomical and physio-chemical features of the four tree aforementioned species.
Task 1.1 – Morpho-anatomical features
The present task will investigate possible changes in plant allometry (e.g., trunk diameter) as well as in microscopic leaf structure
promoted by SI. In particular, leaves will be collected at three developmental stages: young, mature and senescent phase. SI treatments will start in winter, before bud break. Then, during the first year, mature (month 7-8) and senescent leaves (month 10-12) will be monitored, whereas the young leaves will be monitored during the second year of experiments (month 16-17) to understand the effect of SI seasonal exposure. Effects on bud break efficiency and timing will be also evaluated. At the end of the experimental trial (month 21), before the beginning of leaf senescence, plant biomass will be partitioned in root, wood and leaves to understand possible alterations triggered by SI.
Task 1.2 – Physiological traits
The impact of SI will be investigated at physiological level through gas exchanges, water relation parameters, and chlorophyll a fluorescence measurements. Results will allow to depict a clear picture of the light-triggered alteration promoted by SI and to unveil whether the streetlamp developed ad hoc for the project (green-rich light) resulted less impacting than the other two (cold and warm LED lights) over plant/leaf physiology. Leaf photosynthesis and photochemistry will be monitored at pre-down, midday, late evening and during the night to provide a daily profile of photosynthesis in streetlamp-illuminated versus non-exposed individuals. Overall, gas exchange and chlorophyll a fluorescence parameters will unveil possible stomatal as well as biochemical limitations to photosynthesis caused by PSII photochemical efficiency alterations, mesophilic disturbance or stomatal closure.
Task 1.3 – Biochemical investigations
Biochemical analyses will investigate the possible SI-triggered changes in terms of primary carbon metabolism as well as light-dependent C-based secondary metabolites (i.e., flavonoids). In view of the strict interdependence between light and plant pigments (i.e., chlorophylls and carotenoids, including xanthophyll pool) HPLC-based quantification will be conducted in samples collected across the whole day and in the night.
As SI could alter the natural day/night cycle of plants, thereby altering physiological redox state of leaves and in particular chloroplasts. Thus, the evaluation of antioxidant machinery components will be assessed as well as the level of oxidative stress markers (i.e., malondhyaldeyde) in chloroplasts isolated from leaves collected across the day and the night sampling times (see Task 1.2).
WP2 – Effect of SI on lichen performances
As in WP1, the WP2 will deal with the evaluation of the effect of three different streetlamps on the physio-chemical features (Task 2.1) of the two aforementioned lichen species and on their metal uptake capacity (Task 2.2).
Task 2.1 – Physiological and biochemical traits
The impact of SI in lichen transplants will be investigated at physiological level on the lichen photobiont (genus Trebouxia) through chlorophyll a fluorescence measurements, photosynthetic pigments (content, reciprocal ratios and degradation) to deepen the effect of SI on the photosynthetic process of illuminated lichen photobionts. Furthermore, given the symbiotic nature of lichens, specific parameters related to the mycobiont (e.g., ergosterol content) and to the whole thallus (TTC reduction to TPF as indicator of dehydrogenase activity, membrane lipid peroxidation, production of ROS) will be also assessed. Results will allow to depict a clear picture of the light-triggered alteration promoted by SI and to unveil whether one of the three provided streetlamps results as less impacting than the other over lichen physiology.
Also in the case of lichens, photochemistry will be monitored at pre-down, midday, late evening and during the night to provide a daily profile in streetlamp-illuminated versus non-exposed individuals. Non-destructive parameters, such as chlorophyll a fluorescence measurements followed by the analysis of data by the JIP-test will be monitored on monthly basis in relation to the presence/absence of tree canopy. This step will contribute to understand eventual limitations to photosynthesis caused by PSII photochemical efficiency alterations at a fine scale. Destructive tests (evaluation of chlorophylls integrity, ergosterol content, TTC reduction to TPF, membrane lipid peroxidation, production of ROS) will be carried out at the end of relevant stages concerning the trees, namely related to leaves growth and senescence, i.e, months 6-8 and 10-12 (see WP1 - Task 1.1) after the beginning of the treatments and the transplant experiment.
Task 2.2 – Biomonitoring capacity
We will test whether nocturnal light may impair the role of lichens as biomonitors by investigating the performances of the selected species after SI treatments, with a focus on the uptake capacity of heavy metals.
To this purpose, prior to the experiment and after 12 months of SI treatments under the above-mentioned conditions, a batch of samples for each SI condition will be randomly selected and tested for the uptake capacity of divalent heavy metals (suggested elements among those found in lichens from urban environments: Cd, Cr, Pb and Zn). Lichen thalli will be short-term (24 hours) incubated with solutions containing (in the form of cation-Cl2) 10 and 100 mM of Cd2+ Cu2+, Zn2+, as well as Pb2+, tested individually and in combination, allowing cation uptake according to the characteristics (performance) of the thalli. For each sample, 200 mg of dry (living) lichen material are necessary. The experiment will be carried out in triplicate. Since cation uptake involves passive (a physio-chemical uptake influenced by environmental concentrations and chemical affinities) and active processes (linked to lichen metabolism and related to respiration rates and the previous environmental conditions) total, extracellular and intracellular fractions will be assessed by ICP-MS. An alteration of such fractions will likely reflect differences due to previous treatments of the samples (i.e, light treatments) and may reflect a variation of their accumulation (biomonitoring) capacity.
In addition, native samples of X. parietina, will be collected both on trees exposed to SI in their environment and in parallel, on the closest trees not illuminated. Their chemical content will be investigated and compared with a focus on selected elements of toxicological concern generally found in lichens from
urban environments (As, Cd, Cr, Cu, Pb, S, Sb, V, Zn) and Fe, Al (being associated to soil influence on the samples). The peripheral part of the thalli (roughly up to 5 mm from lobe tips) will be selected for the analysis; this choice is foreseen by the protocols generally applied in the field of passive biomonitoring with foliose lichens.
WP3 – Dissemination
A dedicated website will be established at the beginning of the project in order to make available the activities and results of the project to a wider audience of stakeholders. In addition, public communication and scientific dissemination activities will be made public via social networks.
Further, project information will be defined in academic and scientific social networking such as Researchgate and Publons. Members of the research team will disseminate results through the typical channels of academic research like peer-reviewed international scientific journals and international scientific meetings. A final workshop will be organized for disseminate the results of the project.
WP4 – Coordination
The principal Investigator has the responsibility to assure that the project can reach the goals in the due time. The specific activities within this WP will include 1) monitoring the research activities and the use of budget; 2) the organization of kick-off meeting, mid-term and closing meetings; 3) the management of the deadlines, milestones and deliverables; 4) finding effective solutions to unexpected issues. A prompt flow of information between the partners will be ensured, involving them in the decision processes in a shared and transparent manner.
Duration
Beginning: 14/10/2023
Conclusion:
Funding body
Ultimo aggiornamento
06.05.2024