Responses of key root traits in the genusOryzato soil flooding mimicked by stagnant, deoxygenated nutrient solution

Abstract

Excess water can induce flooding stress resulting in yield loss of crops, even in wetland plants such as rice. However, traits from species of wild Oryza have already been used to improve tolerance to abiotic stress in cultivated rice. This study aimed to establish root responses to sudden soil flooding among 8 wild relatives of rice with different habitat preferences benchmarked against 3 genotypes of O. sativa. Plants were raised in hydroponics, mimicking drained or flooded soils, to assess the plasticity of adventitious roots. Traits included were apparent permeance (PA) to O2 of the outer part of the roots, radial water loss (RWL), tissue porosity, apoplastic barriers in the exodermis and root anatomical traits. These were analysed using a plasticity index and hierarchical clustering based on principal components analysis. For example, O. brachyantha, a wetland species, possessed very low tissue porosity compared to other wetland species, whereas dryland species O. latifolia and O. granulata exhibited significantly lower plasticity compared to wetland species and clustered in their own group. Most species clustered according to growing conditions based on PA, RWL, root porosity and key anatomical traits, indicating strong anatomical and physiological responses to sudden soil flooding.

Mitigation of Greenhouse Gas Emissions from Rice via Manipulation of Key Root Traits

“…Anatomical, eco-physiological and genetic studies underpin our current understanding on how rice responds and adapts to flooded soils, and these studies have been pivotal for developing rice cultivars that are better adapted to flooded soils or even complete submergence (Mackill et al 2012 ). Moreover, the evaluation and characterization of undomesticated wild rice species (i.e., Ejiri and Shiono 2020 ; Tong et al 2023 ) increases our chances to breed high-yielding elite cultivars with desirable characteristics and reduced environmental footprint, including a reduction in greenhouse gas emissions.…”

“…Aerenchyma is constitutively formed in the cortex of rice roots, but its proportion significantly increases when roots are formed in flooded soils due to formation of inducible aerenchyma (Colmer et al, 1998 ; 2003a ; Yamauchi and Nakazono 2022 ). Total root porosity (including aerenchyma and small intercellular spaces) of adventitious roots of different rice genotypes increased from 12 to 38% in aerated conditions to 22–48% when growing in anoxic substrates (Colmer et al 1998 ; McDonald et al 2002 ; Colmer 2003a ; Tong et al 2023 ). In adventitious roots of rice, porosity is higher in the basal parts near the root-shoot junction and declines towards the root tip (porosity was c .…”

“…Most experiments published succeed to quantify fluxes of greenhouse gases emitted from soils or plant tissues under specific circumstances but fail to relate these fluxes with the anatomical and/or physiological root characteristics governing internal gas diffusion. Significant variation in root aerenchyma development among rice genotypes exists (Colmer 2003a ), and the identification and characterization of wild rice species with contrasting root anatomical characteristics (Tong et al 2023 ) pave the way for studies on the influence of root traits in the production, oxidation and/or emission of greenhouse gases from flooded paddy soils.…”

“…1 in Jiménez et al 2021b for characteristic radial O 2 loss patterns from roots of rice with or without barriers to radial O 2 loss). There is significant phenotypic variation in the ´tightness` (i.e., permeance to O 2 through exodermal/hypodermal cell layers) of the barrier to radial O 2 loss in adventitious roots of rice (Colmer et al, 1988; Colmer 2003a ; Tong et al 2023 ). Moreover, the barrier to radial O 2 loss can also be formed in L-type lateral roots while these never form in the S-type (Noorrohmah et al 2020 ).…”

Integrated Transcriptomics and Metabolomics Analysis Promotes the Understanding of Adventitious Root Formation in Eucommia ulmoides Oliver

“…AR formation has been deeply studied in the model plants, including A. thaliana [ 44 ], Oryza [ 45 ], and Populus [ 46 ]. In E. ulmoides , the mechanism of the systematic regulation of AR formation by various hormones and key molecules remains elusive.…”