Absorption and distribution of different forms of nitrogen in two legumes and organs

Abstract

Legumes are abundant in the nitrogen deficient desert ecosystems, which is the center of supplying available nitrogen and the important pioneer species in this region. However, the studies on nitrogen uptake and utilization by legumes in desert ecosystems have rarely been reported so far. In this study Astragalus flexus and A. arpilobus, which are widely distributed in the Gurbantunggut Desert, were selected as the research objects. Three different nitrogen forms (15N-NH4+, 15N-NO3-, 15N-glycine) were added to 0-5 cm and 5-15 cm soil layers, respectively, to study the absorption and distribution strategies of different forms of nitrogen in two plants and their organs. The results were as follows: (1) In different soil layers, both plants preferred to absorb nitrate nitrogen, and the maximum absorption rates of A. flexus and A. arpilobus were 3.26, 2.59 μg·g-1·h-1, respectively. (2) In different soil layers, there were significant differences in the uptake and allocation of different nitrogen sources among plant organs (P 15N-glycine > 15N-NH4+, and the contribution rates of nitrate nitrogen to nitrogen absorption of A. flexus ranged from 37% to 41%, while the maximum contribution rate to the nitrogen absorption of A. arpilobus was 45%. (4) There were significant differences in recovery rates of different nitrogen forms between different organs of plants (P stem > root, while in the 5-15 cm soil layer, the rate was leaf > root > stem. In general, in the Gurbantunggut Desert ecosystem, different life forms legumes had both consistency and difference in nitrogen uptake and allocation capacity, and were affected by different soil depths and nitrogen forms. The results provide theoretical basis for nitrogen uptake, utilization and allocation of legumes in arid and semi-arid regions of Xinjiang.

Keywords

• legumes
• plant organ
• isotopic labeling
• nitrogen uptake
• gurbantunggut desert