ABSTRACT
As sessile organisms, plants are constantly challenged by a dynamic growing environment. This includes fluctuations in temperature, water availability, light levels, and atmospheric conditions. In concert with changes in abiotic conditions, plants experience changes in biotic stress pressures, including plant pathogens, viruses, and herbivores. Human-induced increases in atmospheric carbon dioxide (CO2) levels have led to alterations in plant growth environments that challenge their productivity and nutritional quality. Additionally, it is predicted that climate change will alter the prevalence and virulence of plant pathogens, further challenging plant productivity. A knowledge gap exists in the complex interplay between plant responses to biotic and abiotic stress conditions. Closing this gap is crucial for developing climate resilient crops in the future. Here, we review the physiological responses of plants to elevated CO2, temperature, tropospheric ozone (O3), and drought conditions, as well as the interaction of these abiotic stress factors with plant pathogen pressure. Additionally, we describe the crosstalk and trade-offs involved in plant responses to both abiotic and biotic stress, and outline targets for future work to develop a more sustainable future food supply in light of future climate change.
INTRODUCTION
Anthropogenic increases in fossil fuel emissions have led to atmospheric concentrations of carbon dioxide (CO2) that are unprecedented for the last 800,000 years (IPCC, 2021). This has led to unequivocal warming of the global atmosphere, changes in precipitation patterns and extreme weather events, and increased sea level rise leading to coastal flooding (IPCC, 2021). Additionally, other changes in atmospheric constituents, such as the concentration of secondary air pollutants like tropospheric ozone (O3), are also predicted to increase this century (IPCC, 2021). Global climate change will lead to more frequent and extreme heat waves, drought, waterlogging, and associated changes in soil moisture (IPCC, 2021). While the predicted negative impacts of global warming on agricultural productivity and the associated socioeconomic impact on food systems have been well reviewed (e.g., Cushman et al., 2022; Fisher et al., 2005; Hatfield et al., 2011; Vermeulen et al., 2012; Slattery & Ort, 2019), less is known about the significant interactions and trade-offs between and among different climate change-associated abiotic stresses on plant productivity (Rivero et al., 2022). For example, while global warming and associated changes in plant growing conditions have potential negative impacts on yield and productivity especially for the latter half of the 21st century (Challinor et al., 2014; Lobell et al., 2011), elevated CO2 concentrations [CO2] stimulates growth and harvestable grain production in C3 crops (Ainsworth et al., 2008). This, however, comes at a cost of decreased nutritional content in major crop plants (Myers et al., 2014; Soares et al., 2019), but has also been shown to be ameliorated under elevated temperature (Kohler et al., 2019).
Even less is known about these interacting abiotic stress factors in perennial and specialty cropping systems (Leisner, 2020), and about crosstalk between abiotic and biotic stress signaling pathways (Fujita et al., 2006). While there are many unknowns related to the effects of climate change on pathogen spread, evidence indicates there will be enhanced reproductive potential and increased geographic spread of pathogens, which has the potential to lead to changes in disease dynamics and pathogen host ranges, raising concerns of increased disease outbreaks (Garret et al., 2006; Kissoudis et al., 2014). Combined biotic and abiotic stresses can lead to alterations in defense signaling pathways in plants, predisposing plants to increased susceptibility to endemic pathogens, but also potentially new pathogens. Here we briefly review the physiological responses of plants to climate-change related abiotic stress, outline the complex interplay of stress signaling pathways between abiotic and biotic stress pathways related to climate change, and highlight trade-offs and targets for future research efforts and work to enhance resilience in plant development and defense responses considering future climate change.
PHYSIOLOGICAL RESPONSES OF PLANTS TO ABIOTIC STRESS