Subcellular Distribution of Metals within Brassica chinensis L. in Response to Elevated Lead and Chromium Stress

Abstract

Differential centrifugation and synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) microprobe were used to study the distribution of the elements in tissue cross sections of pakchoi ( Brassica chinensis L.) under stress of elevated Pb and Cr. Subcellular fractionation of the different tissues grown in a nutrient solution containing 200 mg L(-1) Pb or 5 mg L(-1) Cr showed that 86.7 and 76.3% of the Pb that accumulated in the roots and shoots, respectively, was contained in the cell wall and vacuoles in those areas. Whereas 75.0% of the Cr that accumulated in the root was contained in the cell wall, 63.1% of the Cr that accumulated in the shoot was found in the vacuoles and cell wall. SRXRF analysis revealed that, when pakchoi seedlings were placed under excess Pb stress, the Pb, Ca, Cu, and Zn were concentrated in the cortex and vascular bundle of the root and mixed Fe-Mn plaques were seen on the surface of the pakchoi root. In the Cr treatment group, Cr, Ca, Mn, and Zn were mainly located in the cortex of the root, whereas in the stem, only Ca, Cu, and Zn were detected at higher levels in the cortex area. Thus, this study provides evidence that, in response to Pb and Cr stress, pakchoi uses cell walls and vacuoles to reduce the transport of these heavy metals through the plant, as well as restrict transport from the root to the stem.

UPTAKE OF HEAVY METALS BY TOMATO PLANTS (Lycopersicum esculentum Mill.) AND THEIR DISTRIBUTION INSIDE THE PLANT

“…The results of this study also showed that all the examined heavy metals especially Cr and Ni accumulated in higher amounts in the roots than in the above-ground parts of a plant. These results agree with results of other authors who examined this issue (Adki et al, 2013;Wu et al, 2013). Gomes et al (2017) reported that plants possess several different strategies to neutralize the negative impact of heavy metals on plants.…”

Localization and Speciation of Chromium in Coptis chinensis Franch. using Synchrotron Radiation X-ray Technology and Laser Ablation ICP-MS

“…The results of this study strongly corroborate previous finding from Cr hyperaccumulator Leersia hexandra , 83.2% of the root Cr was localized in the cell wall fraction 88 . Researches have also shown that other heavy metals are dealt with in similar ways; Pb was accumulated predominantly in the cell walls of roots in the vegetable pakchoi 89 , while Cd was found principally in the cell wall of shoots in Impatiens walleriana 90 .…”

Calcium induces phytochelatin accumulation to cope with chromium toxicity in rice (Oryza sativaL.)

“…Several physiological studies pointed out the role of PCs in the homeostasis and detoxification of Cr and other metals in plants (Shanker et al 2005;Singh et al 2013). Plant removes the toxic effect of Cr by reducing Cr (VI) to Cr (III), followed by complexation of Cr (III) with PC and then this PC-Cr complexes transported to vacuoles (Wu et al 2013). In addition to PC, metallothioneins (MTs), cysteine-rich low molecular weight proteins, also act in Cr detoxification in plants (Shanker et al 2004;Panda and Choudhury 2005).…”