Lead accumulation and tolerance of Moso bamboo (Phyllostachys pubescens) seedlings: applications of phytoremediation

Abstract

A hydroponics experiment was aimed at identifying the lead (Pb) tolerance and phytoremediation potential of Moso bamboo (Phyllostachys pubescens) seedlings grown under different Pb treatments. Experimental results indicated that at the highest Pb concentration (400 μmol/L), the growth of bamboo seedlings was inhibited and Pb concentrations in leaves, stems, and roots reached the maximum of 148.8, 482.2, and 4282.8 mg/kg, respectively. Scanning electron microscopy revealed that the excessive Pb caused decreased stomatal opening, formation of abundant inclusions in roots, and just a few inclusions in stems. The ultrastructural analysis using transmission electron microscopy revealed that the addition of excessive Pb caused abnormally shaped chloroplasts, disappearance of endoplasmic reticulum, shrinkage of nucleus and nucleolus, and loss of thylakoid membranes. Although ultrastructural analysis revealed some internal damage, even the plants exposed to 400 µmol/L Pb survived and no visual Pb toxicity symptoms such as necrosis and chlorosis were observed in these plants. Even at the highest Pb treatment, no significant difference was observed for the dry weight of stem compared with controls. It is suggested that use of Moso bamboo as an experimental material provides a new perspective for remediation of heavy metal contaminated soil owing to its high metal tolerance and greater biomass.

Keywords: Moso bamboo; Pb; Phytoremediation; Scanning electron microscopy; Transmission electron microscopy.

Fig. 1

Effect of Pb on the growth of Moso bamboo seedlings at the time of harvest Plants were treated with various levels (0, 10, 25, 50, 100, 200, and 400 μmol/L) of Pb for 30 d

Fig. 2

Effects of different Pb treatments on dry biomass of Moso bamboo Error bars are standard deviations (n=3). Different letters indicate significant differences (P<0.05) between the treatment and control (CK)

Fig. 3

Total root length (a), surface area (b), root volume (c), and number of tips (d) of Moso bamboo showed different responses to different Pb treatments for 30 d Error bars are standard deviations (n=3). Different letters indicate significant differences (P<0.05) between the treatment and control (CK)

Fig. 4

Scanning electron micrographs of cross-sections of Moso bamboo leaf (a–d), root (e–h), and stem (i–l) treated with 0 and 400 μmol/L Pb for 30 d Control (CK; 0 μmol/L Pb): a, c, e, g, I, and k; 400 μmol/L Pb treated: b, d, f, h, j, and l

Fig. 5

Transmission electron micrographs of the leaf (a–d), root (e–h), and stem (i–l) Ultrathin sections of the Moso bamboo exposed to 0 and 400 μmol/L Pb for 30 d. Control (CK; 0 μmol/L Pb): a, c, e, g, i, and k. 400 μmol/L Pb treated: b, d, f, h, j, and l. Labels: Ch, chloroplast; CW, cell wall; Gr, granum; PG, plastoglobule; M, mitochondrion; PL, plasmalemma; SG, starch grain; NU, nucleus; NUE, nucleolus; V, vacuole; C, cytoplasm; ER, endoplasmic reticulum