Abstract
Potassium in plants accounts for up to 10% dry weight, and participates in different physiological processes. Under drought stress, plant requires more potassium but potassium availability in soil solutes is lowered by decreased soil water content. Forming symbiosis with arbuscular mycorrhizal (AM) fungi not only enlarges exploration range of plant for mineral nutrients and water in soil, but also improves plant drought tolerance. However, the regulation of AM fungi on plant root potassium uptake and translocation from root to shoot was less reported. In current study, the effect of an AM fungus (Rhizophagus irregularis), potassium application (0, 2, and 8 mM), and drought stress (30% field capacity) on Lycium barbarum growth and potassium status was analyzed. Ten weeks after inoculation, R. irregularis colonized more than 58% roots of L. barbarum seedlings, and increased plant growth as well as potassium content. Potassium application increased colonization rate of R. irregularis, plant growth, potassium content, and decreased root/shoot ratio. Drought stress increased colonization rate of R. irregularis and potassium content. Expression of two putative potassium channel genes in root, LbKT1 and LbSKOR, was positively correlated with potassium content in root and leaves, as well as the colonization rate of R. irregularis. The increased L. barbarum growth, potassium content and genes expression, especially under drought stress, suggested that R. irregularis could improve potassium uptake of L. barbarum root and translocation from root to shoot. Whether AM fungi could form a specific mycorrhizal pathway for plant potassium uptake deserves further studies.
Highlights
Potassium is one of the most important mineral element in plants, which accounts for 2–10% of plants dry weight, and its concentration in cytoplasm must be maintained in the range of 100–200 mM to ensure enzymes activities (Leigh and Wyn Jones, 1984)
In order to illustrate the influence of Arbuscular mycorrhizal (AM) fungi on plant potassium uptake and translocation, the transcript of AKT1 and SKOR orthologue genes were analyzed in current study
More than 58% roots of L. barbarum seedlings were colonized by R. irregularis 70 days after inoculation in current study
Summary
Potassium is one of the most important mineral element in plants, which accounts for 2–10% of plants dry weight, and its concentration in cytoplasm must be maintained in the range of 100–200 mM to ensure enzymes activities (Leigh and Wyn Jones, 1984). The accumulated potassium in different parts of AM fungus and mycorrhizal root section suggested that the AM fungi were capable of potassium absorption and transportation from soil to plant root (Scheloske et al, 2004; Pallon et al, 2007; Olsson et al, 2008). The regulation of AM fungi on plant genes in charge of potassium uptake by root and translocation from root to shoot was less reported. In order to illustrate the influence of AM fungi on plant potassium uptake and translocation, the transcript of AKT1 and SKOR orthologue genes were analyzed in current study. The objectives of current study were: (1) to evaluate the combined effect of potassium application, drought, and AM fungus on plant growth and potassium status, (2) to analyze the regulation of AM fungus on the expression of LbKT1 and LbSKOR under different potassium and water conditions
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