Cadmium In Shoots Research Articles

Cadmium Uptake by Winter Wheat Seedlings in Response to Interactions Between Phosphorus and Zinc Supply in Soils

ABSTRACT Effects of application of zinc (Zn) (0, 1, 5, 10 mg kg−1 soil) and phosphorus (P) (0, 10, 50, 100 mg kg−1 soil) on growth and cadmium (Cd) accumulations in shoots and roots of winter wheat (Triticum aestivum L.) seedlings were investigated in a pot experiment. All soils were supplied with a constant concentration of Cd (6 mg kg−1 soil). Phosphorus application resulted in a pronounced increase in shoot and root biomass. Effects of Zn on plant growth were not as marked as those of P. High Zn (10 mg kg−1) decreased the biomass of both shoots and roots; this result may be ascribed to Zn toxicity. Phosphorus and Zn showed complicated interactions in uptake by plants within the ranges of P and Zn levels used. Cadmium in shoots decreased significantly with increasing Zn (P < 0.001) except at P addition of 10 mg kg−1. In contrast, root Cd concentrations increased significantly except at Zn addition of 5 mg kg−1 (P < 0.001). These results indicated that Zn might inhibit Cd translocation from roots to shoots. Cadmium concentrations increased in shoots (P < 0.001) but decreased in roots (P < 0.001) with increasing P supply. The interactions between Zn and P had a significant effect on Cd accumulation in both shoots (p = 0.002) and roots (P < 0.001).

Genotypic Variation in Shoot Cadmium Concentration in Rice and Soybean in Soils with Different Levels of Cadmium Contamination

A pot experiment was conducted to investigate whether the shoot cadmium (Cd) concentration in 11 rice and 10 soybean cultivars varied among 4 soils with different levels of Cd contamination. Significant differences in shoot Cd concentration were found among rice or soybean cultivars grown in the 4 soils. The ranking of the rice cultivars for the shoot Cd concentration varied considerably among the soils. On the other hand, the soybean cultivars were ranked similarly in terms of shoot Cd concentration in the 4 soils. Significant and positive correlations were found between the Cd and Zn concentrations and between the Cd and Mn concentrations in the shoot of rice cultivars, when they were grown in 2 soils with relatively moderate levels of Cd contamination. The shoot Cd concentration in the soybean cultivars, however, was not correlated with the concentrations determined for any of the metals (Zn, Mn, Cu, and Fe) across the 4 soils. Significant and positive correlations between the concentrations of Cd in younger shoots and mature seeds were detected among the soybean cultivars in 2 soils used, unlike among the rice cultivars, indicating that it may be difficult to evaluate the genotypic variation in seed Cd concentration using relatively younger shoots in the case of rice. These results revealed that genotypic differences in shoot Cd concentration in rice or soybean are variable or invariable among soils, respectively.

Oxidative stress and phytochelatin characterisation in bread wheat exposed to cadmium excess

In this work, we first investigated if the bread wheat ( Triticum aestivum L.) cv. Albimonte can be defined as “shoot cadmium excluder”—by comparing the cadmium (Cd) content in leaves and roots and by calculating the shoot-to-root Cd concentration ratio. Furthermore, we evaluated if the exposure to Cd excess could generate oxidative stress in leaves and roots of this cv., in terms of hydrogen peroxide (H 2O 2) accumulation, NAD(P)H oxidation rate, and variations in reduced glutathione (GSH) content and peroxidase (POD, EC 1.11.1.7) activity. Finally, we surveyed possible quali- quantitative differences in thiol-peptide compound pattern between roots and leaves, in order to verify whether phytochelatins (PCs) and related thiol-peptides could contribute in limiting the Cd-induced oxidative stress. Unambiguous characterisation of PCs and related forms present in the root samples was obtained by electrospray ionisation mass spectrometry (ESI-MS) and ESI-tandem MS (ESI-MS/MS). Our results indicate that in leaves the stress generated by the low accumulation of Cd (due to a moderate translocation in planta) seems to be counteracted by the antioxidant response and by the PC biosynthesis. On the contrary, in roots, in spite of the elevated presence of PCs and related thiol-peptide-compounds, the excess of Cd causes a decline in the antioxidant protection of the organ, with the consequent generation of considerable amounts of H 2O 2, a direct agent of oxidative stress.

Shoot Cadmium Accumulation and Photosynthetic Performance of Barley Plants Exposed to High Cadmium Treatments

Barley (Hordeum vulgare L., cv. Ribeka) plants grown in sand culture were exposed for 10 days to high cadmium (Cd) treatments in order to study both shoot Cd accumulation and photosynthetic performance. Cadmium inhibited root dry mass and induced changes in biomass allocation pattern without any effect on biomass accumulation at the whole plant level. The maximal shoot Cd concentration—41 ± 8 mg Cd kg−1 DW—without any visual toxicity symptoms on the shoots was found at 28 mg Cd kg−1 sand. Reduced leaf gas exchange, photosynthetic pigments content and electron transport activity but not altered lipid peroxidation status of thylakoids was, however, detected at the highest treatment—42 mg Cd kg−1 sand. The results indicated good tolerance of barley growth and photosynthetic machinery to Cd, but the shoot Cd accumulation achieved even in the artificial conditions was considered insufficient for short-term phytoextraction.

Genotypic variations in cadmium levels of rice grain

To identify rice grain genotypes with a lower cadmium content, 49 cultivars of rice were tested under upland conditions, using two types of soils contaminated with cadmium (A: alluvial and B: volcanic ash soil) in 1999 and 2000. Results of ranking of grain cadmium concentrations were similar between these 2 years. NIPPONBARE, KOSHIHIKARI, and HU-LO-TAO belonged to the rice grain group with the lowest cadmium contents. KASALATH could be categorized as a variety with a medium cadmium content, hereafter referred to as “medium cadmium variety,” and MILYANG23 and PEH-KUH-TSAO-TU as varieties with high cadmium contents, hereafter referred to as “high cadmium varieties.” These five varieties except for HU-LO-TAO from the above six typical varieties were grown in submerged pots (paddy conditions), and the ranking of the grain cadmium content was almost the same as that in the upland condition pots. These results imply that it may be possible to select paddy rice varieties with a low cadmium content even when growth occurred under upland conditions. The possibility of screening for lower cadmium content in rice grain in solution culture was examined. The shoot cadmium concentrations in solution culture were not significantly lower in NIPPONBARE and KOSHIHIKARI than those of MILYANG23 and PEH-KUH-TSAO-TU after 4 d of cadmium addition. Only PEH-KUH-TSAO-TU showed a higher shoot cadmium concentration than the other varieties after 27 d of cadmium addition. Thus, as a preliminary evaluation, a screening method using solution culture would not be suitable for detecting genotypes with a low cadmium content in grain within 1 month after cadmium addition. Our results suggest that the status of available cadmium in soil differs from that of available cadmium in solution culture. Cadmium distribution for grain (Le., grain cadmium content ratio to total uptake in the terrestrial part of plants) was evaluated among these 5 varieties. KASALATH absorbed a relatively high amount of cadmium, although cadmium distribution to grain in KASALATH was the lowest among the 5 varieties. On the other hand, in MILYANG23, a much higher amount of cadmium was translocated to the grain than in the other 4 varieties, suggesting the existence of genetic variability in cadmium translocation from shoots to grains.

Distribution of cadmium in shoot and root tissues1

Distribution of cadmium in shoot and root tissues1

Localization and Toxic Effects of Cadmium, Copper, and Uranium in Azolla

The storage and distribution of copper, cadmium, and uranium and their effects on ionic contents in roots and shoots of Azolla filiculoides has been studied by x-ray microanalysis. The relative content of copper was eightfold higher in the root than in the shoot, suggesting low mobility of this metal in Azolla plant. Cadmium relative content in the shoot was similar to its content in the root, hence its mobility was relatively high. The absence of significant uranium quantities in the shoot and its relative high content in the root suggest the immobility of this metal from Azolla root. Cadmium formed precipitates with phosphate and calcium in xylem cells of the shoot bundle and caused a two- to threefold increase in the content of phosphate in the root. Uranium in roots and cadmium in shoots were associated with calcium. All three treatments caused losses of potassium, chloride, and magnesium from Azolla roots. Accumulation of heavy metals in Azolla and their mobility from the root to the shoot can be correlated with damage caused by the loss of essential nutrients.

The influence of heavy metals upon the growth of sitka-spruce in South Wales forests

Experiments on sitka-spruce seedlings grown in acidic peaty gley soils under green-house conditions, where the soils where doped with increasing amounts of Cd, Cu and Pb up to maximum levels of metal added of 16 ppm, 32 ppm and 400 ppm respectively, showed that the levels of Cd and Pb in shoots and roots increased with increasing levels in the soil, whereas levels of copper appeared to be independent. The addition of these three metals to the soils did not influence the uptake of other heavy metals, or of the nutrients potassium or calcium. Increases in the shoot cadmium levels significantly reduced the yields of the plant shoots. However, the plant yields were only affected by the highest level of lead that was added to the soil (400 ppm Pb) and unaffected by all the copper treatments (0–32 ppm Cu in the soil).