High Phosphorus Utilization and Silicon Amelioration of Aluminium Toxicity by Puccinellia chinampoensis Ohwi under Sodic Conditions

Abstract

In the rhizosphere of sodic soil, aluminium (Al) and silicon (Si) are present in soluble forms. Hence, plants growing in sodic soils suffer Al toxicity, which can be ameliorated by Si. The aim of this study was to investigate the effect of Al and Si on the growth of Puccinellia chinampoensis Ohwi (P. chinampoensis), a sodic-tolerant grass, under sodic conditions in hydroponic cultivation. Barley (Hordeum vulgare L. cv. Minorimugi) was used as a control. Plant growth under alkaline conditions [pH 10 without Sodium carbonate/bicarbonate (Na2CO3/NaHCO3)] and sodic conditions (pH 10 with Na2CO3/NaHCO3) in the presence and absence of added Al and Si were compared. Phosphorus (P), sulphur (S), Si and potassium (K) contents were then analysed by particle induced X-ray emission. Under sodic conditions, P, S, Si and K uptakes of P. chinampoensis were enhanced, and Al toxicity was alleviated. In addition, Si amelioration of Al toxicity in P. chinampoensis was enhanced under sodic conditions. On the other hand, the uptake of P, S, Si and K of barley was repressed under sodic conditions, and Si amelioration of Al toxicity was weakened. Phosphorus, S, Si, and K uptake in barley was not repressed under alkaline conditions (pH of around 10 and no Na2CO3/NaHCO3 added). The results suggested that sodium ion (Na+) and carbonate/bicarbonate ions (CO32-/HCO3-) repressed barley uptake of ions, such as potassium ion (K+), phosphate ion (PO43-), sulfate ion (SO42-) or silicate ion (SiO44-), and that Al toxicity was enhanced under sodic conditions. In P. chinampoensis, the uptake of ions was activated by Na+ and CO32-/HCO3-, resulting in increased Si amelioration of Al toxicity and Al tolerance by high nutrient uptake. Thus, P. chinampoensis appears to be well adapted to sodic conditions. Further studies of the nutritive properties of sodic-tolerant plants are needed to enable their use in the promotion of revegetation of sodic soils in the future.