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

Abstract

Drought stress forms a major environmental constraint during the life cycle of plants, often decreasing plant yield and in extreme cases threatening survival. The molecular and physiological responses induced by drought have been the topic of extensive research during the past decades. Because soil-based approaches to studying drought responses are often challenging due to low throughput and insufficient control of the conditions, osmotic stress assays in plates were developed to mimic drought. Addition of compounds such as polyethylene glycol, mannitol, sorbitol, or NaCl to controlled growth media has become increasingly popular since it offers the advantage of accurate control of stress level and onset. These osmotic stress assays enabled the discovery of very early stress responses, occurring within seconds or minutes following osmotic stress exposure. In this review, we construct a detailed timeline of early responses to osmotic stress, with a focus on how they initiate plant growth arrest. We further discuss the specific responses triggered by different types and severities of osmotic stress. Finally, we compare short-term plant responses under osmotic stress versus in-soil drought and discuss the advantages, disadvantages, and future of these plate-based proxies for drought.

Screening of Worldwide Barley Collection for Drought Tolerance: The Assessment of Various Physiological Measures as the Selection Criteria

“…Thus, PEG solutions with different concentrations have been widely applied in studies on evaluating and phenotyping of drought tolerance ( Szira et al, 2008 ; Munns et al, 2010 ; Luo et al, 2015 ; Meng et al, 2016 ). However, there is a consideration that osmotic stress is too simple and quick-effect to delegate the complicated and slow-onset drought stress ( Dubois and Inzé, 2020 ). Therefore, it is preferable and recommendable to evaluate the same genotypes under different drought conditions.…”

“…On the other hand, it has been recommended that testing drought tolerance using PEG-stimulated osmotic stress under controlled conditions is useful when working in the field where many factors are not controlled ( Sallam et al, 2018 ). But, PEG solution is very viscous and limits O 2 movement to roots so that the roots become O 2 deficient, which may interfere with ion transport in plant roots ( Munns et al, 2010 ; Dubois and Inzé, 2020 ). Furthermore, the practicability of using PEG-induced osmotic stress to represent drought stress has been increasingly queried by several researches ( Verslues et al, 2006 ; Skirycz et al, 2010 ; Claeys et al, 2014 ; Dubois and Inzé, 2020 ), because PEG solutions may induce the short-term hyperosmotic shock to plants but not the gradually-emerged long-term low water potential stress as soil drying does.…”

“…But, PEG solution is very viscous and limits O 2 movement to roots so that the roots become O 2 deficient, which may interfere with ion transport in plant roots ( Munns et al, 2010 ; Dubois and Inzé, 2020 ). Furthermore, the practicability of using PEG-induced osmotic stress to represent drought stress has been increasingly queried by several researches ( Verslues et al, 2006 ; Skirycz et al, 2010 ; Claeys et al, 2014 ; Dubois and Inzé, 2020 ), because PEG solutions may induce the short-term hyperosmotic shock to plants but not the gradually-emerged long-term low water potential stress as soil drying does. All the above facts suggest that there is no perfect medium to impose the controlled water deficit to plants, all have limitations including pots containing real soil, that is, soil imported from the field.…”

Insight of Transcriptional Regulators reveals the Tolerance Mechanism of Carpet-grass (Axonopus compressus) Against Drought

“…Such behavior may possibly because of drought stress; Axonopus compressus plants had perceived signals rstly, which lead to ABA production, which observed to be translocated to the above-ground parts. The transportation mechanism system in the stem take into action and trigger short-term responses such as stomatal closure [40,43], which will help Axonopus compressus to avert the dehydration and improve water withholding potential under drought stress. Accordingly, the understanding of stress signal and subsequent molecular mechanisms in Axonopus compressus needs to be elucidated in succeeding experiments to reveal the drought-resistance mechanism.…”

Insight of Transcriptional Regulators reveals the Tolerance Mechanism of Carpet-grass (Axonopus compressus) Against Drought

“…Such behavior may possibly because of drought stress; Axonopus compressus plants had perceived the signals, which led to ABA production, which observed to be translocated to the above-ground. The transportation mechanism system in the stem take into action and trigger short-term responses such as stomatal closure [41,44], which will help Axonopus compressus to avert the dehydration and improve water holding capacity under drought stress. Accordingly, the understanding of stress signal and subsequent molecular mechanisms in Axonopus compressus needs to be elucidated in succeeding experiments to reveal the drought-resistance mechanism.…”