Partitioning of zinc, cadmium, manganese and cobalt in wheat (Triticum aestivum) and lupin (Lupinus albus) and further release into the soil

Abstract

The uptake and redistribution of the heavy metals zinc, cadmium, manganese and cobalt are relevant for plant nutrition as well as for the quality of harvested plant products. In the experiments reported here, seedlings of wheat (Triticum aestivum L.) and white lupin (Lupinus albus L.) were radiolabelled for 24 h with 65 Zn, 109 Cd, 54 Mn and 57 Co via one seminal root (wheat) or via the main root (lupin). Plants were afterwards grown on rhizoboxes containing soil. Samples were collected throughout the experiment and analysed afterwards for their radionuclide contents. A strong retention in the labelled part of the root was observed for 57 Co in wheat and lupin and for 109 Cd in lupin, while 65 Zn and 54 Mn were transported to the shoot in both plants. While 65 Zn was redistributed via the phloem from older to younger leaves, 54 Mn accumulated in the first leaves and no major redistribution within the shoot was observed.109 Cd was present in the shoot of wheat but not in the shoot of lupin. The redistribution of 65 Zn, 109 Cd, 54 Mn and 57 Co in the phloem differed between wheat and lupin. The 65 Zn content in the wheat roots appearing after the labelling phase represented 34% of the total content in the plant at the end of the experiment and less than 3% remained in the labelled root, while a high percentage of 65 Zn was retained in the originally labelled part of the main root of lupin. Smaller quantities of 109 Cd, 54 Mn and 57 Co accumulated in all parts of the root system of wheat and lupin. Nevertheless, heavy metals were found in rhizosphere soil (1-2 mm soil around the roots) and bulk soil (no contact with roots) from both plants. Higher quantities of heavy metals were found in the rhizosphere soil close to the labelled part of the root.65 Zn was present in large quantities in the rhizosphere soil close to all parts of the root system of wheat. For both plants, 65 Zn, 109 Cd, 54 Mn and 57 Co were found in the bulk soil indicating that the plant itself might play a role in the redistribution of heavy metals in the soil around its own roots. Phloem-mobile elements may be transported to growing parts of the root system and may reach deeper soil layers. The redistribution of heavy metals in the soil may be in vertical and horizontal directions, at least as far as the root system grows.

Determination of Phytoremediation Potential of Desert Broom Grown in a Mine Tailings Reclamation Project

“…2a, Pb, As, Ni, and Co accumulated by desert broom was retained in the roots and TF values less than 1 demonstrates the limited mobility of Pb, As, Ni, and Co in desert broom. Each plant species might have a unique mechanism against any metal; however, similar results were found in other research for Pb (Fitzgerald et al, 2003), As (Geng et al, 2006), Ni (Nkoane et al, 2005), and Co (Page et al, 2006). The elevated metal concentrations in roots and low translocation to the aboveground tissues in some investigated species might also suggest that they are capable of rather well-balanced uptake and translocation of metals under heavily metal-polluted conditions (Nkoane et al, 2005, Deng et al, 2004).…”

Differences in Cadmium Accumulation and Root Morphology in Seedlings of Japanese Wheat Varieties with Distinctive Grain Cadmium Concentration

“…Chen and Hale (2004) also reported the retranslocation of Cd from the shoot to root. Pineros et al (1998) and Page et al (2006) further showed an efflux of Cd from the root. These factors may be related to the difference in root to shoot translocation of Cd in the wheat varieties used in this study, and these varieties can be useful materials to investigate Cd translocation in wheat.…”

Metal Availability and Chemical Properties in the Rhizosphere of Lupinus albus L. Growing in a High-Metal Calcareous Soil

“…White lupin shoots have been found to accumulate up to 6,100 μg g −1 dry weight (Kerley 2000) without showing any chlorosis symptoms. According to Page et al (2006), Mn is transported in white lupin from the main root to the oldest leaves where it is accumulated. That distribution suggests that Mn is rapidly released from the roots into the xylem and reaches photosynthetically active leaves via the transpiration stream; no redistribution of Mn to other leaves was observed by Page et al (2006).…”

“…According to Page et al (2006), Mn is transported in white lupin from the main root to the oldest leaves where it is accumulated. That distribution suggests that Mn is rapidly released from the roots into the xylem and reaches photosynthetically active leaves via the transpiration stream; no redistribution of Mn to other leaves was observed by Page et al (2006). The slight visual symptoms of chlorosis found in our experiment could be due to a low Fe/Mn ratio in shoots (0.032).…”

“…White lupin is a leguminous species with the ability to fix atmospheric N 2 (Page et al 2006), and this fixation can be affected by environmental factors such as heavy metals in the soil (Castro and Ferreira 2006). Similar N concentrations (Table 1) were found by Dinkelaker et al (1989) in shoots of lupin plants grown in a sterilised calcareous soil fertilised with NO 3 -N (13.2 mg g −1 ) and by Sas et al (2001) in roots (17-18 mg g −1 ).…”