Root growth of crops is altered by climate change

Climate change have a harsh impact on agricultural production, threating food security. Plants perceive, integrate and respond to stress signals differently according to the nature of the combined interaction. This review recaps the current information on the physiological, hormonal, and molecular effects of abiotic stress combination on the roots.

Abiotic stresses have a big impact on root development and functionality, altering the uptake of water and nutrients as well as the root interactions with the microorganisms in the rhizosphere. These changes in RSA and functionality also affect the aerial parts of the plant, altering important physiological and developmental processes like stomatal conductance, photosynthesis or carbon allocation. All these adjustments in the above and below ground must be coordinated to provide a global plant response and enable stress adaptation. In response to different abiotic stresses, roots display shared or unique physiological and morphological responses. Examples of shared changes on RSA and physiology are alterations in root length and depth, changes in lateral root formation and elongation as well as alterations in root hair development and carbon and nutrient root-shoot allocation. Some metabolic changes are also common to several abiotic stresses, like the accumulation of osmoprotectants to avoid intracellular water loss caused by several stresses including drought and salinity. Similarly, under the vast majority of abiotic stresses, ROS accumulate at much higher levels, causing damage to DNA, carbohydrates and proteins. On the other hand, plant cells contain antioxidative compounds and enzymes to prevent this excessive ROS accumulation and balance the oxidative stress response. Another common response to abiotic stresses is the increase in cytosolic Ca2+ levels due to the activation of Ca2+ channels produced in turn by increased levels of ROS and H2O2. These changes in Ca2+ influx are the signal to trigger several cascades of phosphorylation and dephosphorylation by Ca2+-dependent protein kinases. Then, these cascades will transmit the stress signal to the downstream targets of these kinases that includes specific families of transcription factors (TFs) regulating the global stress plant response. Several plant hormones like abscisic acid, jasmonic acid, ethylene or salicylic acid have shown to be the key regulators of abiotic stress responses in roots. But other hormones, like cytokinins, brassinosteroids, auxins and gibberellins, has also been associated with the response to abiotic stresses. On the other hand, abiotic stresses induce global transcriptomic reprogramming to adjust plant growth to the new environmental situation. Thus, plant responses to abiotic stresses also comprise different regulatory gene networks involving specific set of TFs. Lastly, recent investigations have shown that epigenetic mechanisms play an important role in the regulation of abiotic stress responses.

Plants have evolved complex acclimation mechanisms that start with the perception and transmission of the stress signals to the cellular machinery, the subsequent triggering of different signaling pathways and the final activation of an adaptive response. As we have described, some of these acclimation responses are similar between stresses but plants can also trigger responses that are tailored to a particular stress combination. As a consequence, plant response to stress combinations cannot be easily predicted from studying each single stress individually. Moreover, two abiotic stresses that are occurring simultaneously can either aggravate or benefit plant survival and growth. Although most of stress combinations have an additive negative interaction, there are examples of stresses that interact positively like drought and O3 stress or salinity and high CO2. Understanding how crop tolerance mechanisms are adjusted to specific combinations of stresses is important to maintain yield stability under the variable environmental conditions driven by climate change. In this context, root adaptive traits as we described in this review, constitute an attractive target for future breeding programs trying to address cross-tolerance to multiple abiotic stresses related to climate change.

Original Paper: Sánchez-Bermúdez, M., del Pozo, J.C., Pernas, M. 2022. Effects of Combined Abiotic Stresses Related to Climate Change on Root Growth in Crops. 13. DOI: 10.3389/fpls.2022.918537