Source of inorganic N affects the cost of growth in a legume tree species (Virgilia divaricata) from the Mediterrean-type Fynbos ecosystem

作者：Magadlela Anathi; Perez Fernandez Maria A^*; Kleinert Aleysia; Dreyer Leanne L; Valentine Alex J

来源：Journal of Plant Ecology, 2016, 9(6): 752-761.

DOI：10.1093/jpe/rtw015

• phosphate deficiency
• Virgilia divaricata
• N-2 fixation
• mineral N
• C construction costs
• asparagine

Aims
In Mediterranean-type ecosystem, the Cape Fynbos, legumes may be able to switch between soil N and atmospheric N-2 sources during growth to adjust the carbon costs of N acquisition. This study investigated the utilization of different inorganic N sources by Virgilia divaricata, a native legume from the Mediterranean-type ecosystem of the Cape Floristic Region.
Methods
Plants were cultivated in sterile quartz sand, supplied with 25% strength Long Ashton nutrient solution, modified to contain 500 mu M Phosphate. At the phosphate level (500 mu M), plants were treated with 500 mu M NH4NO3 (treatment named N), or grown in N-free nutrient solution and inoculated with effective Burkholderia sp. (Bact.) or treated with combined N sources (500 mu M NH4NO3) and inoculated with effective Burkholderia sp. (N+ Bact.).
Important Findings
The application of NH4NO3 to the legumes resulted in a greater increase in plant dry matter. Carbon construction costs were higher in plants that were supplied with mineral and symbiotic N sources. Maximum photosynthetic rates per leaf area was maintained, irrespective of the N sources. Although the plant roots were nodulated, the plant dependence on N-2 fixation decreased with addition of N. Roots and nodules of the plants solely reliant on N-2 fixation showed an increase in glutamine content. These results show that V. divaricata is highly adapted for growth at the forest margin. Fynbos and possibly anthropic soils by utilizing both atmospheric and soil N sources.

• 出版日期2016-12