Abstract
Copper (Cu) toxicity in plants may lead to iron (Fe), zinc (Zn) and manganese (Mn) deficiencies. Here, we investigated the effect of Si and Fe supply on the concentrations of micronutrients and metal-chelating amino acids nicotianamine (NA) and histidine (His) in leaves of cucumber plants exposed to Cu in excess. Cucumber (Cucumis sativus L.) was treated with 10 µM Cu, and additional 100 µM Fe or/and 1.5 mM Si for five days. High Cu and decreased Zn, Fe and Mn concentrations were found in Cu treatment. Additional Fe supply had a more pronounced effect in decreasing Cu accumulation and improving the molar ratio between micronutrients as compared to the Si supply. However, the simultaneous supply of Fe and Si was the most effective treatment in alleviation of Cu-induced deficiency of Fe, Zn and Mn. Additional Fe supply increased the His but not NA concentration, while Si supply significantly increased both NA and His whereby the NA:Cu and His:Cu molar ratios exceeded the control values indicating that Si recruits Cu-chelation to achieve Cu tolerance. In conclusion, Si-mediated alleviation of Cu toxicity was directed toward Cu tolerance while Fe-alleviative effect was due to a dramatic decrease in Cu accumulation.
Highlights
Micronutrients such as copper (Cu), iron (Fe), zinc (Zn) and manganese (Mn), are essential to all plants, since they participate in numerous metabolic processes
Si-mediated alleviation of Cu toxicity was directed toward Cu tolerance while Fe-alleviative effect was due to a dramatic decrease in Cu accumulation
Our results indicate that both NA and His were increased under conditions of high Cu concentration in the leaves (Cu treatment), whereas only the level of His was increased when the leaf Cu accumulation declined to a moderate level (Cu + Fe treatment)
Summary
Micronutrients such as copper (Cu), iron (Fe), zinc (Zn) and manganese (Mn), are essential to all plants, since they participate in numerous metabolic processes. The interaction between the elements becomes apparent when the excessive level of one of the micronutrients in the growth medium is present so that it may interfere with the uptake, transport and accumulation of the other nutrients, disturbing the overall plant nutrient balance [1]. Plants exposed to overload of Cu are highly prone to the induced deficiency of other essential ions suffering a disturbance of essential metabolic processes [1]. Cu in excess competes for specific binding sites of other metal ions and displace them from their binding sites [2]. Divalent cation uptake transporters such as: Iron-regulated transporter 1
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