Effects of elevated ozone on physiological, anatomical and ultrastructural characteristics of four common urban tree species in China

Abstract

a b s t r a c tFast urbanization has led to ozone (O 3 ) being the main pollutant in summer in most of China. To assess future ground-level O 3 effects on the service of urban greening species and clarify the underlying mechanism of O 3 damage, four common urban greening species, Ailanthus altissima (AA), Fraxinus chinensis (FC), Platanus orientalis (PO) and Robinia pseudoacacia (RP) were exposed to non-filtered air (NF) and to elevated O 3 (E-O 3 ) in open-top chambers. E-O 3 induced visible injury in all species as well as microscopic alterations such as collapse of the palisade parenchyma cells, callose accumulation, or chloroplast and mitochondrial accelerated senescence. E-O 3 significantly reduced light-saturated CO 2 assimilation (A sat ), the maximum activity of Rubisco (Vc max ), the maximum electron transport rate (J max ), and fluorescence parameters such as the quantum yield of noncyclic electron transport ( PSII ), and the quenching of photochemical efficiency of PSII (qP). It also increased total antioxidant capacity, phenolics and ascorbate contents. No significant interaction between O 3 and species was found in photosynthetic performance and antioxidant systems, suggesting that the four species selected were sensitive to O 3 . Of all four species, AA was the most sensitive species due to a combination of earlier injury onset, anatomical features, lower antioxidant responses and higher stomatal conductance. The sensitivity of tree species to O 3 is a factor to be considered for urban greening. Ozone may affect important urban forest ecosystem services by reducing CO 2 assimilation.

A meta‐analysis on growth, physiological, and biochemical responses of woody species to ground‐level ozone highlights the role of plant functional types

“…The first paper on O 3 impacts on Chinese woody species was published in 2006 (He, Ruan, Chen, & Lu, 2006). Since then, more than 60 experimental studies have been carried out in southern and northern China to investigate O 3 effects on woody species native of China or largely cultivated in China-e.g., for ornamental and greening purposes-in terms of gas exchange, chlorophyll a fluorescence, antioxidant system, and growth (e.g., Feng & Li, 2017;Feng et al, 2011;Gao, Catalayud, García-Breijo, Reig-Armiñana, & Feng, 2016;He et al, 2007;Xu, He, Chen, Su, & Huang, 2014;Yan et al, 2010).…”

Elevated ozone concentration decreases whole‐plant hydraulic conductance and disturbs water use regulation in soybean plants

“…, Scoffoni et al 2016). In addition, due to the fact that symptoms are rarely observed in leaf veins under O 3 stress (Zhang et al 2012, Gao et al 2016, it can therefore be inferred that the reduction in K leaf mainly occurs in mesophyll cell where the major resistance to water flow is located (Sack and Holbrook 2006, Sack and Scoffoni 2013, Scoffoni et al 2016).…”

The impact of elevated ozone on the ornamental features of two flowering plants (Tagetes erecta Linn. and Petunia hybrida Vilm.)

“…In this study, plant photosynthetic performance was weakened under O 3 stress, as indicated by the decline in leaf chlorophyll content (Figure 4), requiring more biomass to be allocated to the shoot in order to maintain high levels of photosynthesis. Additionally, O 3 stress obstructs phloem sieve elements by increasing the accumulation of callose, consequently hampering assimilate transport from shoot to root (Calatayud et al, 2011;Gao et al, 2016). Moreover, O 3 stress stimulates the root respiration rate, as suggested by Nouchi et al (1991) and Thwe et al (2013), which subsequently accelerates the consumption of root biomass.…”