Abstract
Mesembryanthemum crystallinum L. (common ice plant) is an edible halophyte. However, if ice plants are used to phytoremediate salinity soil, there are problems of slow initial growth, and a long period before active NaCl uptake occurs under higher salinity conditions. Application of endophytic bacteria may improve the problem, but there remain gaps in our understanding of how endophytic bacteria affect the growth and the biochemical and physiological characteristics of ice plants. The aims of this study were to identify growth-promoting endophytic bacteria from the roots of ice plants and to document the metabolomic response of ice plants after application of selected endophytic bacteria. Two plant growth-promoting endophytic bacteria were selected on the basis of their ability to promote ice plant growth. The two strains putatively identified as Microbacterium spp. and Streptomyces spp. significantly promoted ice plant growth, at 2-times and 2.5-times, respectively, compared with the control and also affected the metabolome of ice plants. The strain of Microbacterium spp. resulted in increased contents of metabolites related to the tricarboxylic acid cycle and photosynthesis. The effects of salt stress were alleviated in ice plants inoculated with the endobacterial strains, compared with uninoculated plants. A deeper understanding of the complex interplay among plant metabolites will be useful for developing microbe-assisted soil phytoremediation strategies, using Mesembryanthemum species.
Highlights
Salinity, which is a major environmental issue in arid and semi-arid regions, imposes stress upon vegetation and exacerbates the effects of other stresses, including water scarcity, nutrient deficiencies, and soil alkalinity [1]
The ice plants could grow in soil containing 50 mM and 200 mM NaCl
When the NaCl concentration reached 350 mM, ice plant growth was inhibited in all three soils
Summary
Salinity, which is a major environmental issue in arid and semi-arid regions, imposes stress upon vegetation and exacerbates the effects of other stresses, including water scarcity, nutrient deficiencies, and soil alkalinity [1]. It is thought that 20% of the global irrigated area is affected by salinization caused by irrigation. In some countries, such as Egypt, Iran and Argentina, salinized soils constitute more than. Salt-removal technologies include physical–chemical methods, such as gypsum-based sodic soil reclamation, and subsurface drainage of water-logged saline soils to remove salts accumulated at the surface [7]. These methods are costly and may have other negative effects on the environment [8]. Many other halophytes, such as Sedum aizoon L. [11], Suaeda salsa [12], Suaeda maritima and Sesuvium portulacastrum [13]), and Salicornia ramosissima [14], are reported to be favorable plants that could be used for the phytoremediation of saline- and heavy metals–contaminated soil
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