Silicate-Mediated Alleviation of Pb Toxicity in Banana Grown in Pb-Contaminated Soil

Abstract

Silicate (Si) can enhance plant resistance or tolerance to the toxicity of heavy metals. However, it remains unclear whether Si can ameliorate lead (Pb) toxicity in banana (Musa xparadisiaca) roots. In this study, treatment with 800 mg kg(-1) Pb decreased both the shoot and root weight of banana seedlings. The amendment of 800 mg kg(-1) Si (sodium metasilicate, Na(2)SiO(3)·9H(2)O) to the Pb-contaminated soil enhanced banana biomass at two growth stages significantly. The amendment of 800 mg kg(-1) Si significantly increased soil pH and decreased exchangeable Pb, thus reducing soil Pb availability, while Si addition of 100 mg kg(-1) did not influence soil pH. Results from Pb fractionation analysis indicated that more Pb were in the form of carbonate and residual-bound fractions in the Si-amended Pb-contaminated soils. The ratio of Pb-bound carbonate to the total Pb tended to increase with increasing growth stages. Treatment with 100 mg kg(-1) Si had smaller effects on Pb forms in the Si-amended soils than that of 800 mg kg(-1) Si. Pb treatment decreased the xylem sap greatly, but the addition of Si at both levels increased xylem sap and reduced Pb concentration in xylem sap significantly in the Si-amended Pb treatments. The addition of Si increased the activities of POD, SOD, and CAT in banana roots by 14.2% to 72.1% in the Si-amended Pb treatments. The results suggested that Si-enhanced tolerance to Pb toxicity in banana seedlings was associated with Pb immobilization in the soils, the decrease of Pb transport from roots to shoots, and Si-mediated detoxification of Pb in the plants.

Performances of Water Management, Foliage Dressing, and Variation Screening in Controlling the Accumulation of As and Cd and Maintaining the Concentrations of Essential Elements in the Grains of Rice Plant

“…Liang et al (2005) found that root dressing with 400 mg kg −1 Si significantly increased the pH of Cd contaminated soil. Similar increases in soil pH after the addition of silicate was also reported in the study of Li et al (2012). Foliage dressing with Se also increased the rhizosphere soil pH of P1.…”

Mitigation of cadmium and arsenic in rice grain by applying different silicon fertilizers in contaminated fields

“…This resulted in the observed significant decrease of Cd concentration in straw and grain. This supports other studies that showed that slag alkaline Si-containing materials at high dosages can induce an increase in soil pH which consequently increases the proportion of non-exchangeable heavy metals Li et al 2012). Another possible explanation is that Si restricted the transport of Cd from roots to shoots.…”

Silicon-Mediated Tolerance to Metal Toxicity

“…In recent studies, Si has been reported to be effective in mitigating Pb toxicity in plants (Araujo et al 2011 ;Li et al 2012b ;Bharwana et al 2013 ). Araujo et al ( 2011 ) showed that Si supply alleviated the inhibitory effect of Pb on the growth of maize.…”

“…Bharwana et al ( 2013 ) found that the addition of Pb (50 μM and 100 μM) to the culture solution caused a severe inhibition of cotton growth, which was fully alleviated by addition of 1 mM Si. Li et al ( 2012b ) reported that soil treatment with 800 mg Pb kg −1 decreased both shoot and root dry weight of banana seedlings, while the amendment of Si at 800 mg kg −1 (as sodium metasilicate) signifi cantly enhanced banana biomass.…”

“…reduction in metal availability via metal immobilization arising from an increase of pH (Galvez et al 1987 ;Chen et al 2000 ;Liang et al 2005 ;Gu et al 2011 ;Li et al 2012b ;Zhang et al 2013a , b ). This is easy to understand and also true when basic sodium metasilicate, slag or alkaline Si-containing materials such as biosolids and coal fl y ash are incorporated into metal-contaminated soils as Si sources (Chen et al 2000 ;Liang et al 2005 ;Gu et al 2011 ).…”