Plasticity in nodal root elongation through the hardpan triggered by rewatering during soil moisture fluctuation stress in rice

Abstract

Rainfed lowland (RFL) rice fields have hardpans and experience soil moisture fluctuations (SMF) stress, which influence root system development. Here, we clarify the expression and timing of the plasticity in nodal root elongation through the hardpan under SMF and its contribution to shoot growth using a shallow-rooting IR64 and its deep-rooting introgression line, YTH304. Under SMF, soil moisture content had negative relationship with soil penetration resistance, regardless of hardpan bulk densities. YTH304 had greater root system below the hardpan than IR64 in hardpan with 1.50 but not in 1.70 g cm−3 bulk density (BD). YTH304 had greater plasticity in nodal root elongation through the hardpan than IR64 under SMF, which was clearly expressed during rewatering. YTH304 also had greater soil water uptake below the hardpan during drought and greater shoot growth than IR64. The results imply that deep root system development during SMF was due to the plasticity in nodal root elongation through the hardpan expressed during rewatering rather than during drought periods. This is against the long standing belief that active root elongation through the hardpan happens during drought. This also implies a need to revisit current root screening methods to identify rice lines with good hardpan penetration ability.

Functional roles of root plasticity and its contribution to water uptake and dry matter production of CSSLs with the genetic background of KDML105 under soil moisture fluctuation

“…Previous studies have shown experimental evidences of genotypic variations in root plasticity expressed in response to heterogeneous soil environments for the adaptation of rice plants (Bañoc et al, 2000a;Siopongco et al, 2008;Kano-Nakata et al, 2013;2017;Kameoka et al, 2015;Menge et al, 2016;Niones et al, 2012;Nguyen et al, 2018;Owusu-Nketia et al, 2018;Suralta et al, 2010Suralta et al, , 2016Suralta et al, , 2018Tran et al, 2014). In this study, the CSSLs showed no significant differences in root system development with the recurrent parent under CWL in both experiments.…”

“…The TRL was analyzed using WinRhizo software (Regent Instruments Inc., Saint-Foy, Canada) (Kameoka et al, 2015;Menge et al, 2016). A pixel threshold value of 175 was set for the root length analysis (Nguyen et al, 2018;Suralta et al, 2018). The root lengths were analyzed according to their diameter classes to estimate the total length of lateral roots having a diameter of <0.3 mm (Yamauchi, Pardales, & Kono, 1996).…”

Evaluation of rice grain yield and yield components of Nona Bokra chromosome segment substitution lines with the genetic background of Koshihikari, in a saline paddy field

“…For this purpose, we used a Salt Effect Index (SEI) for the evaluation of grain yield, yield components and growth parameters (above-ground biomass and harvest index) under salinity by computing the difference in each parameter within each line between control and saline conditions. This equation is adapted from ‘Root Plasticity’ studies (Sandhu et al 2016; Nguyen et al 2018; Suralta et al 2018), where the authors used it to calculate the response of root phenotypic parameters to a stress treatment compared to the control conditions. This SEI is effective when comparing responses of various parameters between control and treatment conditions among genotypes in a split plot design experiment with treatments arranged as main plots, whereas the parameters show genotypic variation under control conditions.…”

Plasticity in root system architecture of rice genotypes exhibited under different soil water distributions in soil profile

“…YTH183 can change its root cone angle to both wide and narrow according to the position of the water supply (Table 2 and Figure 2). Plasticity of the root system development in response to SMF has been studied in terms of root elongation and branching in rice (Kano-Nakata et al, 2013;Nguyen et al, 2018;Niones, Inukai, Suralta & Yamauchi, 2015;Owusu-Nketia et al, 2018;Suralta, Inukai & Yamauchi, 2010;Suralta et al, 2018bSuralta et al, , 2018a. Our study noted that plasticity of root growth angle was also exhibited under different soil water distribution in SMF, while most of the studies are focused on natural phenotypic variability of root growth angle (Bettembourg et al, 2017;Kato, Abe, Kamoshita & Yamagishi, 2006;Uga et al, 2015).…”