Assessing lead and cadmium tolerance of Chenopodium ambrosioides during micropropagation: an in-depth qualitative and quantitative analysis

The tolerance of Chenopodium ambrosioides to some heavy metals under in vitro environment was thoroughly investigated. A micropropagation protocol was developed to facilitate the mass production of plants and to identify metals-tolerant species for potential use in the restoration of polluted areas. Nodal explants exhibited callus formation when treated with N₆-benzyladenin (BA) (1.5 mg/l) and a combination of BA/α-naphthalene acetic acid (NAA) at concentrations of 1.5/1.0 mg/l on the Murashige and Skoog (MS) medium. The optimal shoot formation was achieved with the callus grown on a medium enriched with 1.5/1.0 mg/l BA/NAA, resulting in an impressive number (21.89) and length (11.79 cm) of shoots. The in vitro shoots were rooted using NAA (1.0 and 1.5 mg/l) and were acclimatized in pots with 71% survival rate. After standardizing micropropagation protocol, the in vitro shoots were subjected to various doses of lead nitrate (Pb(NO₃)₂ and cadmium chloride (CdCl₂). Pb(NO₃)₂ and CdCl₂ in the media let to a reduction in shoot multiplication, decreasing from 18.73 in the control group to 11.31 for Pb(NO₃)₂ and 13.89 for CdCl₂ containing medium. However, Pb(NO₃)₂ and CdCl₂ promoted shoot length from 5.61 in the control to 9.86 on Pb(NO₃)₂ and 12.51 on CdCl₂ containing medium. In the case of Pb(NO₃)₂ treated shoots, the growth tolerance index (GTI) ranged from117.64% to 194.11%, whereas for CdCl₂ treated shoots, the GTI ranged from 188.23% to 264.70%. Shoots treated with high level of Pb(NO₃)₂induced reddish-purple shoots, while a low level of Pb(NO₃)₂ induced shoots displayed both green and reddish-purple colors in the same explants. In CdCl₂ treated culture, the toxic effects were narrow leaf lamina, elongated petiole and a dark reddish purple coloration. These findings highlight the remarkable potential of C. ambrosioides to maintain growth and organogenesis even in the presence Pb(NO₃)₂ and CdCl₂ on the MS medium, indicating a high degree of metal tolerance.