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El Rasafi T., Nouri M., Bouda S., Haddioui A.: The effect of Cd, Zn and Fe on seed germination and early seedling growth of wheat and bean. Ekológia (Bratislava), Vol. 35, No. 3, p. 213-223, 2016. This study was conducted to evaluate the effect of metals on wheat and bean species. The method uses seed germination and early seedling growth of these plants in the presence of various levels (10, 50, 100, 250, 500, 750 and 1000 mg/L) of Cadmium (Cd), Iron (Fe) and Zinc (Zn). The inhibition caused by these metals was depending on the concentration used, the metal itself and the plant species. The species had reduced seed germination, root and shoot lengths, tolerance index and percentphyto-toxicity with increasing concentrations of metals. Cadmium was determined to be the most inhibitory metal on these parameters. This metal affected significantly the germination, root and shoot length of the species tested, as well as the tolerance index and percentphytotoxicity starting from 50 mg Cd/l. Under the Iron stress, in general, the inhibition of germination and root length of wheat was reduced from 500 mg Fe/l. The results showed also that the inhibitory effect of increase of Zn levels was seen in root, shoot and tolerance indices. The findings also revealed that the metal toxicity was as follow: Cd > Fe > Zn. Regarding species, the results showed that bean seemed to be more tolerant to the increase of the three metals than wheat.

In the course of our research, aimed at improving sugar beets phosphorus nutrition, we isolated and characterized Streptomyces sp. strains, endemic from sugar beet fields of the Beni-Mellal region, which are able to use natural rock phosphate (RP) and tricalcium phosphate (TCP) as sole phosphate sources. Ten Streptomyces sp. isolates yielded a comparable biomass in the presence of these two insoluble phosphate sources, indicating that they were able to extract similar amount of phosphorus (P) from the latter for their own growth. Interestingly, five strains released soluble P in large excess from TCP in their culture broth whereas only two strains, BP, related to Streptomyces bellus and BYC, related to Streptomyces enissocaesilis, released a higher or similar amount of soluble P from RP than from TCP, respectively. This indicated that the rate of P released from these insoluble phosphate sources exceeded its consumption rate for bacterial growth and that most strains solubilized TCP more efficiently than RP. Preliminary results suggested that the solubilization process of BYC, the most efficient RP and TCP solubilizing strain, involves both acidification of the medium and excretion of siderophores. Actinomycete strains possessing such interesting RP solubilizing abilities may constitute a novel kind of fertilizers beneficial for plant nutrition and more environmentally friendly than chemical fertilizers in current use.

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In this work three heavy metals: cadmium (as CdSO4), cobalt (as CoCl2) and zinc (as ZnSO4), were used to determine and compare their toxicity towards two subspecies of barley (Hordeum vulgare subsp. vulgare L. and Hordeum vulgare subsp. distichum L.), focusing on seeds germination, seedlings growth, and cytological parameters. The results indicate that the effect of these heavy metals depends on the metal kind, the metal concentrations and the plant subspecies. Generally, in the case of H. vulgare, the heavy metal salts understudy did not influence significantly seed germination and seedling growth parameters. However, these metal salts influence significantly these parameters for H. distichum. The cytological test showed significant decrease (p < 0.05) in the mitotic index among the increase of the heavy metal concentrations when evaluated with the control for H. vulgare and H. distichum. Consequently, H. vulgare seemed to be more tolerant of the increase of the three heavy metals concentrations than H. distichum.

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