Abstract
There is a demand for an increase in crop production because of the growing population, but water shortage hinders the expansion of wheat cultivation, one of the most important crops worldwide. Polyethylene glycol (PEG) was used to mimic drought stress due to its high osmotic potentials generated in plants subjected to it. This study aimed to determine the root system architecture (RSA) plasticity of eight bread wheat genotypes under osmotic stress in relation to the oxidative status and mitochondrial membrane potential of their root tips. Osmotic stress application resulted in differences in the RSA between the eight genotypes, where genotypes were divided into adapted genotypes that have non-significant decreased values in lateral roots number (LRN) and total root length (TRL), while non-adapted genotypes have a significant decrease in LRN, TRL, root volume (RV), and root surface area (SA). Accumulation of intracellular ROS formation in root tips and elongation zone was observed in the non-adapted genotypes due to PEG-induced oxidative stress. Mitochondrial membrane potential (∆Ψm) was measured for both stress and non-stress treatments in the eight genotypes as a biomarker for programmed cell death as a result of induced osmotic stress, in correlation with RSA traits. PEG treatment increased scavenging capacity of the genotypes from 1.4-fold in the sensitive genotype Gemmiza 7 to 14.3-fold in the adapted genotype Sakha 94. The adapted genotypes showed greater root trait values, ∆Ψm plasticity correlated with high scavenging capacity, and less ROS accumulation in the root tissue, while the non-adapted genotypes showed little scavenging capacity in both treatments, accompanied by mitochondrial membrane permeability, suggesting mitochondrial dysfunction as a result of oxidative stress.
Highlights
Increasing the world wheat production by 2050 by 1.6% per year, when the population would be expanding to 9 billion, is facing a lot of obstacles because of climate change [1]
This study focused on the ability of the Root system architecture (RSA) of different bread wheat genotypes to adapt to extended osmotic stress, and the relationship between osmotic stress-induced reactive oxygen species (ROS) overproduction in root tips and ∆Ψm as a source of adenosine triphosphate (ATP) to produce more adapted roots
The continuous severe osmotic stress of Polyethylene glycol (PEG) 6000 to wheat roots resulted in significant repression of RSA traits, causing oxidative imbalance marked with antioxidant enzyme enhancement as a manifestation of proposed programmed cell death (PCD)
Summary
Increasing the world wheat production by 2050 by 1.6% per year, when the population would be expanding to 9 billion, is facing a lot of obstacles because of climate change [1]. Plants unable to escape from unfavorable conditions due to being sessile must be able to adapt to environmental challenges. During their evolution, plants evolved tremendous capabilities to sense alterations around themselves and rapidly respond by changing their growth directions [4]. Deeper root system genotypes can access deep soil profile more than the shallow ones, resulting in a cooler canopy and higher grain yield performance under the conditions of normal, moderate, and severe drought stresses [7]. The leaf area and shoot biomass were affected in small root system genotypes in the early growth stages as a result of drought stress, where better performance was observed in high vigor-rooted genotypes [8]. Selection for RSA plasticity under water stress conditions could be a point of interest for plant breeding programs for better water consumption and adaptation to abiotic stresses [10], which became an image-based high-throughput phenotypic technique, where a high set of genotypes can be evaluated in less time [11,12]
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