Metal accumulation, growth and nutrition of Vernonia polyanthes exposed to lead nitrate and arbuscular mycorrhizal fungi

Abstract

The association between plants and arbuscular mycorrhizal fungi (AMF) can be used to bioremediate areas contaminated by metals. The objectives of this work were to evaluate the lead (Pb2+) phytoaccumulation capacity, morpho-physiology and nutrition responses of Vernonia polyanthes exposed to a solution amended with concentrations of lead nitrate and arbuscular mycorrhizal fungi. The treatments consisted of increasing doses of Pb2+ as lead nitrate [Pb(NO3)2], two strains of AMF and an absolute control without lead and AMF. Lead negatively affected some morphophysiological variables, reduced 27.3, 25.63, 30.60, and 56.60% shoot length, root collar diameter, number of leaves and leaf area, respectively, besides reducing decreasing chlorophyll a. Lead accumulated in the shoot and roots, the latter at the highest concentrations. However, the translocation factor was above 1, indicating low efficiency. The bioaccumulation factor referring to the roots were above 1. The fungi colonization rate was low, 3.31% for Gigaspora margarita and 2.33% for Acaulospora morrowiae. However, the absorption of lead increased, reflecting in lower values of chlorophyll a, dry mass of root and diameter. Results indicated that the arboreal species V. polyanthes tolerate high concentrations of lead and can accumulate significant amounts in the roots. AMF increase the accumulation of lead in the shoot and can be used in projects aimed at the phytoextraction of metals.

Pb uptake, accumulation, and translocation in plants: Plant physiological, biochemical, and molecular response: A review

“…The nutrient uptake can be reduced due to variations in the physiological activities of plants or the presence of Pb, which may create ionic competition (e.g., those ions having the same atomic size as Pb). According to Morais, Boechat [ 104 ]), minerals having similar radii, like K + and Pb + ions (K + : 1.33 Å and Pb 2+ : 1.29 Å), enter into the plants through similar potassium channels. Likewise, Pb influences –SH groups and K + -ATPase of proteins within the cell membranes, which results in the discharge of potassium ions from the plant roots, while nitrogen efflux is not affected by Pb [ 104 ].…”

“…According to Morais, Boechat [ 104 ]), minerals having similar radii, like K + and Pb + ions (K + : 1.33 Å and Pb 2+ : 1.29 Å), enter into the plants through similar potassium channels. Likewise, Pb influences –SH groups and K + -ATPase of proteins within the cell membranes, which results in the discharge of potassium ions from the plant roots, while nitrogen efflux is not affected by Pb [ 104 ]. Generally, the inorganic nitrogen concentration of all plant parts is reduced due to the rate-limiting enzymes and slow nitrate reductase activity during the nitrate (NO 3 ) reductase process [ 105 , 106 ].…”