Effect of cadmium on growth and concentrations of cadium, ascorbic acid and sulphydryl groups in durum wheat cultivars

By using two durum wheat cultivars (Triticum durum L. cvs. Balcali-85 and C-1252) a nutrient solution experiment was carried out to study i) genotypic variation in cadmium (Cd) tolerance, ii) Cd concentrations in plants, and iii) the role of ascorbic acid and non-protein SH groups (SH: sulphydryl) in Cd tolerance. Plants were grown under controlled climatic conditions for 15 days and subjected to increasing Cd supply (0, 6, 30, 75 and 150 µM). Of the two cultivars, C-1252 showed greater sensitivity to Cd toxicity as judged from the severity of Cd toxicity symptoms on leaves. Increasing Cd supply markedly reduced the shoot and root dry weight of both cultivars, and these decreases were more marked in C-1252. Cd concentrations of plants were strongly increased by enhanced Cd supply, especially in the roots. C-1252 tended to have greater amounts of Cd in the shoots, but lower amounts in the roots than Balcali-85. Ascorbic acid concentrations in the roots and shoots were similarly affected by increasing Cd supply in both cultivars. SH concentrations were similar in the shoots of Balcali-85 and C-1252, and showed a slight increase due to Cd treatments. However, in the roots, Cd supply resulted in dramatic increases in concentrations in the SH groups, particularly in Cd-tolerant Balcali-85. The results indicate that SH-containing compounds (e.g., phytochelatins) and the retention of Cd in the roots are possibly involved in the expression of high Cd tolerance in durum wheat cultivars

Valve Replacement Due To Tricuspid Valve Anomalies In Corrected Transposition

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Cardiac Rhabdomyoma In A Newborn. Two-Dimensional Echocardiographic Diagnosis

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Shoot biomass and zinc/cadmium uptake for hyperaccumulator and non-accumulator Thlaspi species in response to growth on a zinc-deficient calcareous soil

Thlaspi caerulescens is one of the best-known heavy metal hyperaccumulating plant species. It exhibits the ability to extract metals from soils and accumulates them in shoots at extremely high concentrations, particularly zinc (Zn) and cadmium (Cd). Using T. caerulescens (J. and C. Presl, ecotype Prayon) and a closely related non-accumulator species T. arvense, greenhouse experiments were carried out to study shoot growth (dry matter production) and Zn and Cd uptake from a severely Zn-deficient calcareous soil (DTPA-Zn: 0.09 mg kg-1 soil) supplemented with increasing amounts of Zn (0, 0.05, 0.5, 5, 25 and 75 mg kg-1 soil) and Cd (0 and 25 mg kg-1 soil). Shoot dry matter production of T. caerulescens was severely depressed by Zn deficiency, while in T. arvense, Zn deficiency slightly reduced growth. At the lowest Zn supplies (0 and 0.05 mg Zn kg-1 soil), T. caerulescens showed very severe Zn deficiency symptoms, including decreased leaf size and development of chlorosis and whitish-brown necrosis on the younger leaves. These symptoms were slight in T. arvense. At the highest Zn supply, leaves of T. caerulescens did not show any symptoms, but in T. arvense there were some necrotic patches on the margins of older leaves, probably due to Zn toxicity. With increasing Zn supply from 0 to 75 mg kg-1 soil, shoot dry matter production was increased by 4-fold in T. caerulescens and only 1.3-fold in T. arvense. Supply of Cd resulted in marked decrease in shoot growth of T. arvense, particularly under low Zn supply, but had no effect on the growth of T. caerulescens. At the low soil Zn levels (< 0.5 mg Zn kg-1) shoot Zn concentrations were lower in T. caerulescens compared with T. arvense, and were below 10 mg Zn kg-1 dry weight. However, at the high supplies of Zn (> 5 mg Zn kg-1), shoot Zn concentrations were considerably higher in T. caerulescens than T. arvense. Increase in Zn supply from 0 to 75 mg kg-1 enhanced shoot Zn concentrations by 84-fold in T. caerulescens and only 8-fold in T. arvense. Shoot Zn concentrations of both species were not affected by Cd supply, while increase in Zn supply did not affect Cd concentrations in shoot of T. caerulescens, but markedly reduced them in T. arvense. The results demonstrate that T. caerulescens is extremely sensitive to Zn deficiency in soils, but tolerant to excessive accumulation of Zn and also Cd in shoot, while T. arvense is tolerant to Zn deficiency but not to accumulation of Zn and Cd in shoot. Hyperaccumulation of Zn in T. caerulescens possibly depends on the existence of high concentrations of plant-available Zn in soils, which suggests that root-based mechanisms associated with increasing metal availability in the rhizosphere (e.g., rhizosphere acidification or release of Zn-mobilizing organic compounds from roots) only play a minor role in metal hyperaccumulation by T. caerulescens. The findings also suggest that the processes causing the metal hyperaccumulation trait in T. caerulescens also cause this plant species to be sensitive to Zn deficiency stress. © 2003 Elsevier Science Ireland Ltd. All rights reserved