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Nitrogen management under increased atmospheric CO2 concentration in cucumber (Cucumis sativus L.): ameliorating environmental impacts of fertilization
Abstract
In the last years, the atmospheric CO
2
concentration has increased significantly, and this increase can cause changes in various physiological and biochemical processes of plants. However, the response of plants to elevated CO
2
concentration (e[CO
2
]) will be different depending on the nitrogen form available and the plant species. Therefore, hydroponic trials on cucumber plants, with two CO
2
concentrations (400 and 1000 ppm) and two nitrogen sources (NO
3
−
/NH
4
+
; 100/0 and 90/10), were conducted. Physiological parameters—such as gas exchange, GS, GOGAT and GDH activities, cation composition, soluble sugar and starch content- were measured. The results showed that when plants were grown with NH
4
+
and e[CO
2
], parameters such as photosynthesis rate (A
CO2
), instantaneous water use efficiency (WUEi), the content of NH
4
+
, Ca
2+
and Mg
2+
, and the concentration of starch, were higher than in control plants (irrigated with nitrate as sole nitrogen source and ambient CO
2
concentration (a[CO
2
])). Furthermore, an improvement in N assimilation was observed when the GS/GOGAT pathway was enhanced under these conditions (NH
4
+
and e[CO
2
]). Thus, our results contribute to the reduction of the negative environmental impacts of the use of nitrogen fertilizers on this crop, both by reducing nitrogen leakage (eutrophication) and greenhouse gas emissions.