Physiological trait networks enhance understanding of crop growth and water use in contrasting environments

Abstract

Plant function arises from a complex network of structural and physiological traits. Explicit representation of these traits, as well as their connections with other biophysical processes, is required to advance our understanding of plant‐soil‐climate interactions. We used the Terrestrial Regional Ecosystem Exchange Simulator (TREES) to evaluate physiological trait networks in maize. Net primary productivity (NPP) and grain yield were simulated across five contrasting climate scenarios. Simulations achieving high NPP and grain yield in high precipitation environments featured trait networks conferring high water use strategies: deep roots, high stomatal conductance at low water potential (“risky” stomatal regulation), high xylem hydraulic conductivity and high maximal leaf area index. In contrast, high NPP and grain yield was achieved in dry environments with low late‐season precipitation via water conserving trait networks: deep roots, high embolism resistance and low stomatal conductance at low leaf water potential (“conservative” stomatal regulation). We suggest that our approach, which allows for the simultaneous evaluation of physiological traits, soil characteristics and their interactions (i.e., networks), has potential to improve our understanding of crop performance in different environments. In contrast, evaluating single traits in isolation of other coordinated traits does not appear to be an effective strategy for predicting plant performance.

Breeding crops for drought-affected environments and improved climate resilience

“…The term drought is widely used to refer to a severe deficit of available water relative to crop requirements, at one or more stages during the crop lifecycle, which can have a negative impact on crop productivity and quality ( Figure 2 ; Campos et al, 2004 ; Passioura, 2006 ; Blum, 2009 , 2011a , 2011b ; Sinclair, 2011 ; Boyer et al, 2013 ; Lobell et al, 2014 ; Gaffney et al, 2015 ). To understand the impact of water availability on the occurrence of drought within the agricultural environment, to enable breeding for drought resistance, and in turn to understand the impact of any changes in crop productivity on the sustainability of the current and future agricultural systems, characterizing the quantity and timing of water availability, relative to crop requirements throughout the crop lifecycle for agricultural systems, is a foundational requirement ( Chapman et al, 2000 ; Rosegrant et al, 2009 ; Blum, 2011a ; Chenu et al, 2011 ; Boyer et al, 2013 ; Kholová et al, 2013 ; Ray et al, 2013 , 2015 ; Cooper et al, 2014a , 2014b ; Lobell et al, 2014 ; Van Ittersum et al, 2016 ; Rodell et al, 2018 ; Washburn et al, 2021 ; Gleason et al, 2022 ; Messina et al, 2022a , 2022c ).…”

“…We adopt the same convention with respect to crop breeding for improved levels of drought resistance ( Cooper et al, 2020 , 2023 ; Messina et al, 2022a ). That is, consideration should be given to targeted breeding to improve drought resistance when the total supply of water (from stored soil moisture, rainfall, and irrigation) available to a crop during its lifecycle is below the crop demand needed to achieve consistent harvestable yields of at least 80% of the potential yield in the target agricultural environment ( Ludlow and Muchow, 1990 ; Fukai and Cooper, 1995 ; Campos et al, 2004 ; Messina et al, 2011 , 2022a , 2022b ; Van Ittersum et al, 2013 ; Cooper et al, 2014a , 2020 , 2021a , 2021b , 2023 ; Fischer et al, 2014 ; Gleason et al, 2022 ). Here, we consider trait networks to be coordinated combinations of multiple traits, which together operate in ways that contribute to enhanced responses of crops to specific environments, or a range of environmental conditions that occur within a target population of environments (TPEs), beyond the responses that can be achieved by the individual traits operating in isolation ( Hammer et al, 2006 ; Cooper et al, 2009 , 2021a ; Tardieu et al, 2021 ; Gleason et al, 2022 ).…”

“…That is, consideration should be given to targeted breeding to improve drought resistance when the total supply of water (from stored soil moisture, rainfall, and irrigation) available to a crop during its lifecycle is below the crop demand needed to achieve consistent harvestable yields of at least 80% of the potential yield in the target agricultural environment ( Ludlow and Muchow, 1990 ; Fukai and Cooper, 1995 ; Campos et al, 2004 ; Messina et al, 2011 , 2022a , 2022b ; Van Ittersum et al, 2013 ; Cooper et al, 2014a , 2020 , 2021a , 2021b , 2023 ; Fischer et al, 2014 ; Gleason et al, 2022 ). Here, we consider trait networks to be coordinated combinations of multiple traits, which together operate in ways that contribute to enhanced responses of crops to specific environments, or a range of environmental conditions that occur within a target population of environments (TPEs), beyond the responses that can be achieved by the individual traits operating in isolation ( Hammer et al, 2006 ; Cooper et al, 2009 , 2021a ; Tardieu et al, 2021 ; Gleason et al, 2022 ). One of the opportunities we consider herein is the development of crop growth models as both a framework and an enabling transdisciplinary tool to investigate traits and trait networks and their potential for applications to accelerate plant breeding for drought resistance and to enhance trait discovery contributions to improved climate resilience ( Cooper and Hammer, 1996 ; Hammer et al, 2006 , 2019 ).…”

“…Discovery strategies and methodologies for identifying traits and networks of traits contributing to on-farm drought resistance, as targets to accelerate the improvement of crop yield performance, have received significant attention from a range of discipline-centered perspectives; including molecular biology and plant physiology ( Blum, 1988 , 2011a ; Ludlow and Muchow, 1990 ; Fukai and Cooper, 1995 ; Campos et al, 2004 ; Ribaut, 2006 ; Cattivelli et al, 2008 ; Messina et al, 2011 ; Jordan et al, 2012 ; Mace et al, 2012 ; Borrell et al, 2014 ; Guo et al, 2014 ; Luo et al, 2019 ; Liedtke et al, 2020 ; Liu and Qin, 2021 ; Simmons et al, 2021 ; Gleason et al, 2022 ; Welcker et al, 2022 ). Often this has been done without a clear definition of drought within the target drought-affected agricultural environments of the TPE.…”

“…Often this has been done without a clear definition of drought within the target drought-affected agricultural environments of the TPE. The crop physiological framework used to investigate potential contributions of traits to crop performance within water-limited environments for agricultural systems has been continually refined with experience ( Sinclair, 2000 , 2011 ; Passioura, 2006 ; Blum, 2009 , 2011a , 2011b ; Hammer et al, 2009 , 2020 ; Messina et al, 2009 , 2011 , 2015 ; Cooper et al, 2014a ; 2020 ; Gleason et al, 2022 ). Furthermore, improved drought resistance recently has received renewed emphasis as an important target to develop climate-resilient crops ( Reynolds, 2010 ; Blum, 2011a ; Chapman et al, 2012 ; Ray et al, 2015 ; Hammer et al, 2021 ; Langridge et al, 2021 ; Messina et al, 2022a , 2022c ).…”