Methodology of Drought Stress Research: Experimental Setup and Physiological Characterization

Abstract

Drought is one of the major stress factors affecting the growth and development of plants. In this context, drought-related losses of crop plant productivity impede sustainable agriculture all over the world. In general, plants respond to water deficits by multiple physiological and metabolic adaptations at the molecular, cellular, and organism levels. To understand the underlying mechanisms of drought tolerance, adequate stress models and arrays of reliable stress markers are required. Therefore, in this review we comprehensively address currently available models of drought stress, based on culturing plants in soil, hydroponically, or in agar culture, and critically discuss advantages and limitations of each design. We also address the methodology of drought stress characterization and discuss it in the context of real experimental approaches. Further, we highlight the trends of methodological developments in drought stress research, i.e., complementing conventional tests with quantification of phytohormones and reactive oxygen species (ROS), measuring antioxidant enzyme activities, and comprehensively profiling transcriptome, proteome, and metabolome.

Keywords: Drought stress; drought models; drought tolerance; oxidative stress; phytohormones; polyethylene glycol (PEG); stress markers.

Figure 1

The main drought resistance strategies employed by plants to counter water deficit periods (drought escape, drought avoidance, and drought tolerance) and the main steps of the plant response to dehydration.

Figure 2

Experimental drought models based on osmotic stress and established by supplementation of growth medium with polyethylene glycol (PEG): (A) Lemna minor model, established with aqueous growth medium supplemented with PEG6000 ([68]); (B) Brassica napus model, established with aerated aqueous culture supplemented with PEG8000; and (C) agar-based PEG infusion Arabidopsis thaliana model, established by overlaying solidified agar medium with PEG8000 solution for five days.

Figure 3

(A) The main pathways of reactive oxygen species (ROS) generation in plants and (B) the major pathways of plant enzymatic antioxidant defense. SOD, superoxide dismutase; CAT, catalase; APx, ascorbate peroxidase; MDHA, monodehydroascorbate; MDHAR, monodehydroascorbate reductase; DHA, dehydroascorbate; DHAR, dehydroascorbate reductase; GSH, reduced glutathione; GSSG, oxidized glutathione; GR, glutathione reductase.