Interaction ammonium-nitrate: Response to oxidative stress in chicory plants

The aim of this work was to study, as a function of the different availability of nitrogen in the reduced form, mineral and organic, the induction of the synthesis of some ROS-scavenging molecules and the evolution of some enzymatic activities such as ascorbate peroxidase (APX) and polyphenoloxidase (PPO). 
Chicory seedlings were grown in nutritive solution for 35 days in controlled conditions. On the 14th day, one third of the plants was transferred into a nutritive solution containing (NH4)2SO4 60 mM, one third was transferred into a medium containing Urea 60 mM, and the remaining was let grow into the nutrition solution, as a control. Three samplings of leaves were performed, respectively after 21, 28 and 35 days of growth.
The urea and ammonium sulphate-treated samples showed higher ascorbic acid and polyphenol contents than the control, together with a lower anthocyanins content. APX showed the highest activity in the urea-treated samples, while the highest PPO activity was to refer to samples treated with ammonium sulphate.
The variations of the organic components showed the incidence of the nitrogen supply in the reduced form on the cell redox potential, confirming the importance of fertilization for obtaining high amounts of antioxidant molecules.
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Comparing Mineral and Organic Nitrogen Fertilizer Impact on the Soil-Plant-Water System in A Succession of Three Crops

In the belief that the investigation of the whole system helps to avoid the risk of incomplete or misleading responses resulting from the analysis of the single segments, a research was conducted in a succession of three crops (lettuce, red chicory and celery) to investigate  in an integrated approach the different response of the soil-plant-water system to mineral and organic nitrogen fertilization. The experimental plan included the application of two amounts of fertilizer, corresponding to 240 and 360 kg ha-1 N under mineral or organic form per crop cycle, plus a control, in three replications.Mineral N resulted more promptly available to plants and increased the fresh and dry weight and protein content in leaves of the three crops while no significant difference in the tissue moisture content between the treatments was found. The inspection of combined data resulting from soil, plant and water analysis and from N budget demonstrates that altogether more mineral N was released in soil and water from the organic fertilizer while more N was uptaken by plants with the mineral fertilizer.Nitrogen uptake efficiency and N use efficiency in fact were highest in the mineral fertilized plots while surplus N was only found with the organic fertilization.Microbial population in the soil was unaffected by the type and amount of fertilizers; on the contrary, enzymatic activity responded positively to organic N while was depressed by the synthetic N form.  The results suggest that the use of organic N integrated with mineral N at the appropriate crop stages is the solution to be recommended

Influence of different nitrate and iron availabilities on phosphoenolpiruvate carboxilase and malate dehydrogenase in roots of maize (Zea mays L.) plants

The effect of the different nitrate (NO3) availability on some enzymatic activities has been evaluated in iron (Fe) deficient and iron sufficient maize plants (Zea mays L.) in order to evaluate the induction of Fe sensitiveness to enzymatic activities. The apoplast reactions may be altered due to the different nitrate availability. Two experimental tests were done on maize plants grown in nutrient solution with different NO3 availability and with Fe-sufficiency and Fedeficiency. Phosphoenolpiruvate carboxilase (PEPcase) and malate dehydrogenase activities, for the reaction determined in citosol, by NO3 uptake, showed different responses according to Fe availability. The different nitrate availability caused a difference in the acid content. These results justifies the higher energy demand to activate membrane carriers under stress conditions for the reduced nitrate availability