Effects of Different Inorganic Nitrogen Sources of Iris pseudacorus and Iris japonica on Energy Distribution, Nitrogen, and Phosphorus Removal
Rongrong Duan, Deke Xing, Tian Chen, Yanyou Wu
Abstract
High- and low-affinity transport systems are the main pathways for the transportation of NO 3 – and NH 4 + across intracellular membranes. NO 3 − and NH 4 + are assimilated through different metabolic pathways in plants. Fifteen ATP molecules are hydrolyzed in the metabolic process of NO 3 – ; however, only five ATP molecules are hydrolyzed in that of NH 4 + . In this research, seedlings of Iris pseudacorus and Iris japonica were used as the experimental materials in the NO 3 – :NH 4 + = 30:0, NO 3 – :NH 4 + = 28:2, NO 3 – :NH 4 + = 27:3, NO 3 – :NH 4 + = 15:15, NO 3 – :NH 4 + = 3:27, and NO 3 – :NH 4 + = 0:30 treatments at the 7.5 mmol·L −1 the total nitrogen content (TN). The intracellular free energy was represented by physiological resistance (R) and physiological impedance (Z) according to the Nernst equation and could conveniently and comprehensively determine the cellular metabolic energy (G B ). The maximum absorption rate (V max ) and Michaelis constant (K m ) for NH 4 + and NO 3 – uptake were calculated according to the kinetic equation. The results showed that the cellular metabolic energy (G B ) of I. pseudacorus was 1 to 1.5 times lower than that of I. japonica at each treatment on the 10th day. The G B values of I. pseudacorus and I. japonica seedlings increased with increasing NH 4 + concentration. However, there was a turning point at the NO 3 – :NH 4 + = 15:15 treatment for the cellular metabolic energy of I. pseudacorus and I. japonica . Correlation analysis showed that the value of cellular metabolic energy was negatively correlated with the V max and K m for NO 3 – uptake, whereas it was positively correlated with that for NH 4 + uptake. These results demonstrate that the NO 3 – :NH 4 + = 27:3 treatment level was the most suitable for I. pseudacorus and I. japonica . This indicates that the greater cellular metabolic energy is the most suitable for plant growth when the concentration of ammonium or nitrate had no significant difference at treatment. These results provide a simple and rapid solution for removal of nitrogen by determination of cellular metabolic energy.