Source–sink balance and carbon allocation below ground in plants exposed to ozone

Abstract

Contents Summary 213 Introduction 213 Source–sink model: carbohydrate signaling 214 Effect of ozone on above‐ground sources and sinks 216 Decreased allocation below ground 218 Carbon flux to soils 220 Soil food web 223 Summary, conclusions and future research 223 Acknowledgements 223 References 223 Summary The role of tropospheric ozone in altering plant growth and development has been the subject of thousands of publications over the last several decades. Still, there is limited understanding regarding the possible effects of ozone on soil processes. In this review, the effects of ozone are discussed using the flow of carbon from the atmosphere, through the plant to soils, and back to the atmosphere as a framework. A conceptual model based on carbohydrate signaling is used to illustrate physiological changes in response to ozone, and to discuss possible feedbacks that may occur. Despite past emphasis on above‐ground effects, ozone has the potential to alter below‐ground processes and hence ecosystem characteristics in ways that are not currently being considered.

Responses of evergreen and deciduous Quercus species to enhanced ozone levels

“…Also in Quercus pyrenaica, root biomass (and the ratio between above-ground and root biomass) was more importantly affected than above-ground biomass. Ozone effects on roots and/or on the above-mentioned ratio have been reported as a consequence of reduction in CO 2 assimilation but also of photoassimilate allocation from source tissues (leaves) to sink tissues (roots) (Andersen, 2003). Under natural conditions, root reduction and changes in biomass partitioning in tree species may reduce resistance to windthrow (Broadmeadow and Jackson, 2000).…”

Structure and function of rhizosphere and non-rhizosphere soil microbial community respond differently to elevated ozone in field-planted wheat

“…EO 3 not only causes losses to crop yield but can also significantly reduce the allocation of assimilates into the root. This reduction in root biomass would influence the entry of organic matter into the soil (Andersen, 2003). EO 3 reduces litter quality and rates of decay.…”

Effects of elevated O3 concentration on winter wheat and rice yields in the Yangtze River Delta, China

“…For example, the US National Crop Loss Assessment Network (NCLAN) and European Open Top Chamber Programme (EOTCP) have shown significant yield losses of major crops in USA and Europe. Investigations of crop responses to elevated O 3 concentration in terms of phenology, physiology, production and yield have confirmed that elevated O 3 could accelerate crop senescence, decrease photosynthesis, reduce biomass and carbon allocation into roots, and cause yield loss (Morgan et al, 2003;Andersen, 2003;Fiscus et al, 2005;Ashmore, 2005;Feng et al, 2008;Feng and Kobayashi, 2009). Although there are differences in O 3 sensitivity among crops, there are a considerable number of crops sensitive to elevated O 3 concentrations and subject to yield loss.…”