Partial and full root-zone drought stresses account for differentiate root-sourced signal and yield formation in primitive wheat

Abstract

Background Partial and full root-zone drought stresses are two widely used methods to induce soil drying in plant container-culture experiments. Two methods might lead to different observational results in plant water relation, such as non-hydraulic root-sourced signal (nHRS). We compared partial and full stress methods to induce nHRS in two diploids (MO1 and MO4) and two tetraploids (DM 22 and DM 31) wheat varieties under pot-culture conditions. Partial root-zone stress (PS) was performed using split-root alternative water supply method (one half wetting and the other drying) to induce the continuous operation of nHRS, and full root-zone stress (FS) was exposed to whole soil block to induce periodic operation of nHRS since jointing stage. Results We tested the two drought methods whether it influenced the nHRS mediated signalling and yield formation in primitive wheat species. Results showed that partial root-zone stress caused more increase in abscisic acid (ABA) production and decline in stomatal closure than full root-zone stress method. The incline in ABA was closely related to triggering reactive oxygen species (ROS) generation, and reducing cytokinin synthesis which, thereby, led to crosstalk with other signalling molecules. Furthermore, PS up-regulated the antioxidant defense system and proline content. Water use efficiency and harvest index was significantly increased in PS, suggesting that PS was more likely to simulate the occurrence of nHRS by increasing the adaptive strategies of plants and closer to natural status of soil drying than FS. Conclusion These findings lead us to conclude that partial root-zone stress method is more feasible method to induce nHRS which has great capacity to reduce water consumption and enhance plant adaptation to constantly changing environment. These observations also suggest that different root-zone planting methods can be considered to improve the plant phenotypic plasticity and tolerance in water-limited rainfed environments. Electronic supplementary material The online version of this article (10.1186/s13007-019-0461-5) contains supplementary material, which is available to authorized users.

Plant growth under suboptimal water conditions: early responses and methods to study them

“…Fourth, the central drought-responsive hormone ABA has historically grown as the most obvious candidate for root-to-shoot signaling, although recent pieces of evidence lead to question this (reviewed by Pérez-Alfocea et al, 2011;McAdam et al, 2016a;McAdam et al, 2016b). Increased ABA production upon osmotic stress and drought has been observed extensively in multiple species (reviewed in Waadt et al, 2014;Batool et al, 2019a;Batool et al, 2019b;Brunetti et al, 2019;Khadka et al, 2019;Takahashi and Shinozaki, 2019). ABA levels are increased in roots and in the xylem sap, most likely as a result of increased transcription of NCED3, the gene encoding the rate-limiting ABA biosynthesis enzyme (Brunetti et al, 2019).…”

“…upon mutation of the important RBOH-D enzyme, are more sensitive to salt stress (Huang et al, 2019). Short-term accumulation of ROS has now been reported in multiple species upon exposure to different types of osmotic stress, although the evidence for a ROS burst under PEG and mannitol is rather limited or contradictory (Leshem et al, 2007;Si et al, 2010;Tamás et al, 2010;Uzilday et al, 2014;Ben Rejeb et al, 2015a). Overall, studies that performed ROS measurements Downloaded from https://academic.oup.com/jxb/advance-article-abstract/doi/10.1093/jxb/eraa037/5714152 by Ghent University user on 27 January 2020 A c c e p t e d M a n u s c r i p t 9 in different species report a fast but transient ROS wave ranging from minutes to 12 h following stress exposure.…”

“…As a result, water transport is reduced, further sustaining the hydraulic signal along the root up to the shoot, where this decrease in water potential is perceived (reviewed in Rodrigues et al, 2019). However, several lines of evidence suggest that root-to-shoot signaling following stress still occurs when the water potential is maintained by watering parts of the roots or by adjusting the osmotic potential, thereby strongly suggesting the presence of nHRSCs (Davies and Zhang, 1991;Nonami et al, 1997;Tang and Boyer, 2002;Parent et al, 2010;Bonhomme et al, 2012;Batool et al, 2019a;Batool et al, 2019b). The current view is that the earliest response to mild osmotic stress is dominated by nHRSCs, whereas the longer-term response, or when the stress is more severe, is sustained by hydraulic signals (Schachtman and Goodger, 2008;Pérez-Alfocea et al, 2011;Batool et al, 2019a;Batool et al, 2019b).…”

“…Via the rapid induction of above-described mechanisms, leaf water content and osmotic potential are only mildly affected during the first two days of osmotic stress, but eventually show a clear reduction 72 h following exposure to severe salt stress, and likely longer when the stress is milder (Fig. 1v) (Ellouzi et al, 2014;Ben Rejeb et al, 2015a).…”

Root Adaptation via Common Genetic Factors Conditioning Tolerance to Multiple Stresses for Crops Cultivated on Acidic Tropical Soils

“…Due to the sessile nature of plants, evolutionary adaptations have enabled plants to develop sophisticated mechanisms to tolerate or avoid drought. When plants sense water deficit in the surrounding environment, it leads to the generation of drought stress signals ( Blackman and Davies, 1985 ; Kuromori et al, 2014 ; Batool et al, 2019 ). These primary and secondary drought response signals are perceived by receptor molecules which leads to direct changes in the expression of genes or expression of TFs that regulate expression drought-responsive genes, which ultimately leads to drought adaptation ( Kuromori et al, 2014 ).…”