Growth and physiological responses to ozone and mild drought stress of tree species with different ecological requirements

Abstract

An open-top chamber experiment was carried out in Curno (Northern Italy) in 2004 and 2005 on seedlings of Fagus sylvatica (FS), Quercus robur (QR), and an ozone-sensitive Populus (POP) clone, to investigate the role of two stress factors: tropospheric ozone and water shortage. Treatments were filtered air to achieve a 50% reduction in the environmental ozone concentrations (charcoal filtered, CF); and non-filtered air, with a 5% reduction in the environmental ozone concentrations (non-filtered, NF). Overall ozone exposure (AOT40) in open air (April-September) was 26,995 ppb h in 2004 and 25,166 ppb h in 2005. The plants were either watered (W)or not watered (dry, D). We investigated the above-ground biomass, tree-ring growth, stable carbon isotopes ratio, i.e. d 13 C of tree rings, and the photosynthetic parameter Driving forces (DF ABS ), derived from chlorophyll a fluorescence analysis. Ozone-induced growth reduction (in terms of biomass) in POP, and that reduction was more pronounced in D plots. A synergistic effect of ozone and drought stress was evidenced by DF ABS in POP and QR, but not in FS. The water availability was revealed as the main factor influencing the isotopic ratio d 13 C. In droughtstressed seedlings, the increase in d 13 C value was accompanied by the reduction in stomatal conductance and increased DF ABS . Fast-growing plant species with high water requirements are more susceptible to ozone and drought stress.

Nitrogen partitioning in oak leaves depends on species, provenance, climate conditions and soil type

“…This result is consistent with other studies, e.g. Vivin & Guehl (1997) and Pollastrini et al. (2010) who also found increased δ 13 C ratios in Q. robur in response to water deprivation.…”

Assessing the Impact of Ozone on Forest Trees in An Integrative Perspective: Are Foliar Visible Symptoms Suitable Predictors for Growth Reduction? A Critical Review

“…There is likely an interaction during the growing season between O 3 stress, the exposure to high solar intensity radiation, and the onset of the leaf senescence process, which leads to the decline of the photosynthesis and therefore to the decline of biochemical defense [96]. Plants in which the growth and reproductive processes occur in the first part of the season can show the late-season onset of FVS, avoiding any significant growth reduction [25,74]. Contrarily, the plants with continuous growth over the whole season, such as poplar, are more susceptible to the reduction of biomass accumulation [70].…”

Functional traits and adaptive capacity of European forests to climate change

“…Growth (height, stem diameter, crown dieback and overall biomass storage), survival and phenology were the most measured parameters to compare the responses of different provenances both in natural and experimental conditions. Among the physiological traits, water use efficiency (instantaneous -WUE i -and time integrated WUE by δ 13 C analysis) has been measured by several authors to characterize the responses to drought(Farquhar et al, 1989; Gessler et al, 2009;Pollastrini et al, 2010Pollastrini et al, , 2013 Lauteri et al, 2004; Michelot et al, 2011, Máguas et al, 2011, together with chlorophyll content (for ex., bySPAD readings, Brendel et al, 2008) and photosynthetic properties (chlorophyll fluorescence, gas exchange, seeMurchie and Lawson, 2013, Roussel et al, 2009a,b;Guidi and Calatayud, 2014). Leaf Mass per Area (LMA) and foliar nitrogen content demonstrated to be sensitive phenotypic parameters.…”