Red-leafed species for urban "greening" in the age of global climate change

AbstractUrban trees provide vital ecosystem services such as mitigating heat island, improving air quality by removing various air pollutants, capturing rainwater, and acting as topsoil carbon storage. The aesthetic value of urban trees is also another feature that has to be considered in the context of urban greening. Classical criteria for the selection of urban trees have to respond to new challenges imposed to the cities in a near future. Global climate change factors increase the harshness of our cities, and thereby the plant resilience to abiotic stresses has also to be seriously considered for planning the urban greening. Red-leafed species, characterized by the permanent presence of foliar anthocyanins, show a greater tolerance to different environmental cues than green-leafed species commonly used in our cities. In addition, red tree species own a great aesthetic value which has been underestimated in the context of urban areas, especially in the harsh Mediterranean cities. In this study, we emphasize the "privilege of being red" from different point of view, in order to drive the attention to the possibility to increase the use of red-leafed species for urban "greening". Some possible negative aspects related to their use are rebutted and the direction of future researches are proposed

Different Summer and Autumn Water Deficit Affect the Floral Differentiation and Flower Bud Growth in Apricot (Prunus armeniaca L.)

In deciduous fruit species, floral bud initiation, differentiation and organogenesis take place during the summer–autumn season that precedes anthesis. Among factors able to modify the regularity of these processes, water availability represents a crucial aspect. This investigation aimed to assess the influence of different summer and autumn water deficit and re-watering treatments on floral morphogenesis, xylem vessel differentiation and quality of flower buds. Trials were carried out on two-year-old potted apricot trees (cv. ‘Portici’) which were submitted to different regimes: (i) fully irrigated plants; (ii) stressed plants in June (S1), July (S2) and October (S3) followed to re-watering. Midday stem water potential was used to determine water status, and leaf gas exchanges were measured during trials. Histological analyses on floral differentiation, xylem progression within flower buds and biological observations were carried out. Both summer water stress periods affected the floral differentiation leading to a temporary shutdown. The S1 trees were able to recover the development of meristematic apices while S2 had a strong delay. All drought treatments caused a slower xylem progression, variations in bud size, blooming entity and flower anomalies. Results particularly highlights the importance of water availability also in early autum

Chlorophyll Fluorescence, Photoinhibition and Abiotic Stress: Does it Make Any Difference the Fact to Be a C3 or C4 Species?

Chlorophyll fluorescence analysis is one of the most powerful and widely used techniques to study the effect of stresses on the photosynthetic process. From the first utilization, the Fv/Fm ratio has been largely used as a sensitive indicator of plant photosynthetic performance. Decreases of this index are indicative of the reduction of photosystem II (PSII) efficiency, namely photoinhibition. In the last 20 years, application of chlorophyll fluorescence has been largely improved, and many other informative parameters have been established to detect PSII photochemical efficiency and the partitioning of light energy to alternative dissipative mechanisms (qE, energy-dependent quenching; qZ, zeaxanthin-dependent quenching and qI, photoinhibitory quenching; qH, sustained photoprotective antenna quenching; qM, quenching dependent to chloroplast movement; qT, light harvesting complexes II–I state-transition) such as the recently developed “photoprotective power” of non-photochemical quenching (pNPQ). This review reports a brief description of the main chlorophyll fluorescence parameters and a wide analysis of the current bibliography on the use of different parameters which are useful to detect events of PSII photoinhibition. In addition, in view of the inherent differences in morpho-anatomical, physiological and biochemical features between C3 and C4 metabolism, possible differences in terms of photoinhibition between C3 and C4 plant species under stress conditions are proposed. The attempt is to highlight the limits of their comparison in terms of susceptibility to photoinhibition and to propose direction of future research which, assisted by chlorophyll fluorescence, should improve the knowledge of the different sensitivity of C3 and C4 to abiotic stressors

Physiochemical responses of Ailanthus altissima under the challenge of Verticillium dahliae: elucidating the decline of one of the world’s worst invasive alien plant species

Natural infections of Verticillium spp. (Fungi, Ascomycota) on Ailanthus altissima have suggested to consider the biological control as a promising strategy to counteract this invasive plant, which is otherwise difficult to control by traditional mechanical and chemical treatments. Verticillium wilt is able to lead plants to death, throughout a pathogenic mechanism including vessel occlusions and production of degrading enzymes and phytotoxins. In this study, a 10 weeks open air pot experiment was set to investigate the ecophysiological and biochemical responses of Ailanthus trees artificially inoculated in the trunk with the V. dahliae strain VdGL16, previously isolated in Central Italy from the same host. Inoculated plants showed visible injuries starting from 2 weeks post inoculation (wpi), that progressively developed until a final severe defoliation. The fungal infection rapidly compromised the plant water status, and photosynthesis was impaired due to both stomatal and mesophyll limitations from 4 wpi, with subsequent detrimental effects also on PSII activity. Moreover, the disease altered the translocations of nutrients, as confirmed by cation and carbohydrate contents, probably due to a consumption of simple sugars and starch reserves without replacement of new photosynthesized. An accumulation of osmolytes (abscisic acid and proline) and phenylalanine (a precursor of phenylpropanoids) was also reported at 8 wpi, this being a response mechanism that needs to be further elucidated. However, the activation delay of such defence strategy inevitably did not avoid the premature defoliation of plants and the decline of physiochemical parameters, confirming the key role of Verticillium in Ailanthus decay

The use of red species for urban “greening” in the age of climate change

The red/purple colour of some plant species is due to the presence of anthocyanins, a colourful class of flavonoids widely spread in the Plantae kingdom. Beside a doubtless aesthetic value of anthocyanin-rich species, the presence of these pigments confers them peculiar physiological and biochemical properties which make red species usually more tolerant to some environmental stresses, as occur in Mediterranean area. The ability of anthocyanins to partially absorb a proportion of light striking the mesophyll (mainly green and yellow wavebands) represents a useful feature against a condition of excessive light which not only occurs when plants are subjected to high irradiances, but also when other stressors (e.g., high temperature, low water availability) impair the photosynthetic process. The work elucidates as the presence of anthocyanins determines morpho-anatomical, biochemical and physiological effects. In particular, the roles of these pigments are described comparing the leaf ontogenesis of two genotypes of Prunus cerasifera, one with red (var. Pissardii) and one with green leaves (clone 29C). Red-leafed Prunus resulted better protected, especially during the leaf senescence. The presence of anthocyanins also promotes a delayed leaf senescence (4-week-longer leaf lifespan) which is a well-appreciated feature in the context of urban “greening”

Natura abhorret a vacuo: Proposta di riqualificazione delle aree verdi Polo Didattico Piagge - Pisa

Riassunto analitico Il lavoro si è svolto seguendo diverse fasi. In prima battuta è stato compiuto un lavoro di analisi che ha interessato sia il contesto territo- riale di riferimento dell’area oggetto di intervento, sia i luoghi oggetto di intervento. A tale scopo, attraverso la consultazione di documentazione storica d’archivio, di cartografia e di foto aeree, è stato possibile rico- struire le vicende storiche che hanno interessato l’area negli ultimi tre secoli. Questa fase, di carattere prettamente analitico, ha inoltre permes- so di ricostruire uno stato di fatto ‘‘certo’’ dell’area, dato il susseguirsi di ampliamenti e nuove costruzioni, avvenuti a partire dall’originario nucleo ottocentesco; In seconda battuta è stato ricostruito un quadro delle norme e delle prescrizioni presenti negli strumenti della pianificazione urbanistica e territoriale (Piano Strutturale, Regolamento Urbanistico, Piano di Indi- rizzo Territoriale). Infine tutte le informazioni raccolte nelle preceden- ti fasi sono state utilizzate per formulare una proposta progettuale che consentisse di ridurre le criticità riscontrate nell’area e allo stesso tempo di soddisfare le esigenze manifestate dall’Ateneo. Abstract he project has been carried out by fulfilling different phases. Firstly, it has been completed an analysis covering either the whole territory and the specific territory of our interest. As concerns the latter, it has been possible to track historical happenings that have been taking place on this area over the last three centuries through a consultation of historical archive datas. Moreover, this analytical phase enabled us to reconstruct how this site has been developing and expand since the original construction on the 18th century. Secondly, we studied the whole corpus of laws conducting the site mana- gement (Town Planning Scheme, City Planning Rules, Territorial Plan). Finally, the whole amount of gathered information in the previous pha- ses have been used in order to frame a project proposal meant to reduce the site criticalities and, simultaneously, to satisfy University’s priorities

Anthocyanin presence influences physiological and metabolic leaf processes in a red morph of Prunus cerasifera Ehrh.

Red or green leaves might differ in photoprotective mechanisms and, also in the photosynthetic rates to different environmental stress conditions. The debate on the ecological role of foliar anthocyanins is controversial in the scientific community and their photoprotective versus other potential roles still remains a point to be solved. Moreover, the high cost in carbon skeletons required for the anthocyanin biosynthesis raises questions about their possible role as sugar-buffers. For this purpose, four experiments were conducted using two Prunus cerasifera morphs. One morph is characterised by green leaves (P. cerasifera clone 29C; GLP) and the other is characterised by red leaves (P. cerasifera var. pissardii; RLP) due to the presence of anthocyanins. The research aim was understanding the possible physiological and metabolic influences of anthocyanin presence in leaves. Firstly, leaves of P. cerasifera morphs, at three leaf developmental stages, young, mature and senescent (1, 7 and 13-week-old, respectively), were analysed in terms of photosynthetic rate, carbon metabolism and photoprotective mechanisms. The goal was to test whether anthocyanin-equipped leaves perform better than anthocyanin-less leaves and whether photoprotection is the primary role of epidermally-located anthocyanins, using for the first time a recently developed parameter of chlorophyll fluorescence (qPd). Anthocyanins contributed to leaf photoprotection throughout the leaf development but were tightly coordinated with carotenoids. Besides their photoprotecting role, we propose that epidermal anthocyanins may be principally synthetised to maintain an efficient carbon-sink strength in young and senescent leaves, thus extending the RLP leaf lifespan. In the second experiment, a transcriptomic approach has been exploited on green (GLP) and red (RLP) leaves of P. cerasifera from mature to senescent (7 and 13-week-old, respectively). Our analysis revealed 3,070 differentially expressed genes (DEGs), between mature and senescent stage in GLP, whereas red morph showed a slightly higher gene regulation (4,925 DEGs). Significant differences were detected in cellular metabolism of red leaves compared to green: genes involved in photosynthetic processes (e.g. transcripts coding for chlorophyll binding proteins) were highly down-regulated in green genotype, whereas transcripts involved in anthocyanin biosynthesis (e.g. flavonoid 3-O-glucosyltransferase) were up-regulated exclusively in red leaves. In conclusion, RNA-seq analysis suggests that in P. cerasifera red genotype, there is a gene regulation and molecular pathways to cope with the senescence processes in order to promote a delayed leaf ontogenesis compared to the green one. In the third experiment, to elucidate the possible role exerted by anthocyanins against an abiotic stress, the physiological biochemical responses of mature leaves to a severe PEG6000-induced water stress prolonged for 20 days in the two morphs of P. cerasifera were evaluated. After 10 days of the treatment, the reduction in photosynthetic rate was 83.4 and 76.5% in GLP and RLP, respectively, as compared to their relative controls. In both the morphs, the decrease was attributable mostly to stomatal closure but also to a reduction of PSII photochemical efficiency. Analysis of leaf sugar pattern revealed that stress promoted biosynthesis of anthocyanins paralleled to slight increments of sucrose in red-morph leaves at an early stage of the stress whereas anthocyanin-less green-morph leaves exhibited a severe accumulation of soluble sugars. It is possible that a part of carbon assimilated by red-morph leaves was invested into anthocyanin synthesis and this, in turn, lowered accumulation of soluble sugars and limited sink-induced photoinhibition. In conclusion, a positive effect given by anthocyanin presence, in terms of light abatement and photosystem II (PSII) protection, was observed, and also the evidence that the sugar-buffering hypothesis proposed for anthocyanins might make the difference in terms of drought sensitivity between red versus green leaves is provided. In the 4th experiment, shoots from the two P. cerasifera morphs were girdled to understand the role of leaf anthocyanin on photosynthesis, photoprotection and sugar metabolism. Shoot girdling was operated in order to evaluate the anthocyanin influence on the sugar accumulation promoted by girdling. Leaf gas exchange, carbohydrate and anthocyanin concentration were measured daily during the three days after girdling. On the first day at 12:00, net photosynthesis and stomatal conductance were only reduced in girdled green-morph (29 and 33 %, respectively) which also showed higher soluble sugar concentrations than controls. Girdled red morph showed the first reduction of A390 only at 18:00 with no significant differences in sucrose, glucose and fructose concentration. However, girdling highlighted the constitutive ability of girdled RLP to produce more sorbitol than starch if compared to respective GLP. The increase in anthocyanin concentration detected in girdled RLP at the second and third day had contributed in lowering the glucose and fructose accumulation that, together to the constitutive ability of RLP to produce more sorbitol than starch, influenced the circadian leaf starch metabolism and also attenuated the feedback down-regulation of photosynthesis. The effectiveness of non-photochemical quenching (pNPQ) also revealed the ability of anthocyanins to photoprotect PSII from supernumerary photons reaching the chloroplast. Overall, a sugar-buffering role exerted by anthocyanins might have positively influenced the feedback regulation of photosynthesis and, on another hand, anthocyanin accumulation also improved the PSII photoprotection from excitation energy excess. This study represents a starting point to understand the probable link between photosynthesis regulation through sugar-signalling and anthocyanin upregulation. In summary, besides the classical role proposed for anthocyanins as sunscreen compounds, as confirmed in these experiments, a possible modulation of sugar metabolism was proposed, that might further give a wider meaning of “leaf protectants” to this versatile class of flavonoids. This study opens a wider perspective in which anthocyanin synthesis limits the increase in leaf sugars during stress conditions, and at the same time ‘sunscreening’ the leaf, all of this to limit the excitation pressure on PSII reaction centers

First characterization of the formation of anthocyanin–ge and anthocyanin–B complexes through UV–Vis spectroscopy and density functional theory quantum chemical calculations

The occurrence of anthocyanin (ACN) and metal (Me) complexes has been widely supported by many research works while the possibility that ACNs bind to metalloids (Mds) is yet to be proven. Here, metalloids (H3BO3 for B; GeO2 for Ge) were added to cyanidin-based solutions at pH 5, 6, and 7 and ACN–Md stoichiometric ratios of 1:1, 1:10, 1:100, and 1:500, and UV–vis transmittance spectroscopy as well as density functional theory (DFT) calculations were performed to test this hypothesis. Ge and B addition caused bathochromic and hyperchromic shifts on ACN UV–vis spectra, particularly pronounced at pH 5 and a 1:500 (ACN:Md) ratio. ACN–Me complexation reactions have been evaluated where Ge showed a higher capability to bind to ACNs than B. Among the complexes envisioned, those labeled as b1, b2, and b3 feature UV–vis spectra compatible with experiments. The combination of experimental and computational data offers for the first time evidence of the formation of ACN–Md complexesXunta de Galicia | Ref. GRC2019/24Universidade de Vig