Plants require nitrogen (N) within the soil to produce high yields. However, the transport mechanism of nutrients from root medium to plant and the response of plant nitrogen tissue to nitrogen uptake have not been identified so far. The experiments in this study were performed in summer of 2005 and 2006 in order to define the mechanism of nutrient uptake and specify the response of plant nutrient content in Phragmites japonica.The results suggest that the mayor part of nitrogen absorption is due to an active uptake process. The influx is subject to negative feedback on high external concentration and reaches a maximum uptake rate after 6-8 hours of exposure. The response of leaf N content to NO 3 -uptake not only proves the uptake process based on plant demand but also appears to be independent with external concentration and uptake rate. The results also imply the fact that plants may have sufficient capacity to store nutrients.

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