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THE EFFECT OF DIFFERENT INORGANIC NITROGEN SOURCES AND PLANT AGE ON THE COMPOSITION OF BLEEDING SAP OF PHASEOLUS
R J Thomas1, U Feller1, K H Erismann1
1Pflanzenphysiologisches Institut, Universität Bern, Altenbergrain 21, CH-3013, Bern, Switzerland.
The New Phytologist
|November 5, 2022
Summary
Plant nitrogen (N) sap content in Phaseolus vulgaris differs based on the nitrogen source. Ammonium nitrate fertilization resulted in the highest sap N concentration and fastest growth, indicating optimal nutrient uptake.
Area of Science:
- Plant Physiology
- Plant Nutrition
- Agricultural Science
Background:
- Nitrogen is a crucial macronutrient for plant growth and development.
- Understanding nitrogen assimilation and transport in plants is vital for optimizing crop yields.
- The form of inorganic nitrogen supplied can significantly influence plant metabolism and growth.
Purpose of the Study:
- To investigate the impact of different inorganic nitrogen sources (nitrate, ammonium, ammonium nitrate) on the nitrogen composition of bleeding sap in Phaseolus vulgaris.
- To determine how varying external nitrate concentrations affect sap nitrogen composition.
- To correlate nitrate reductase activity with sap nitrogen content during plant development.
Main Methods:
- Plants (Phaseolus vulgaris) were grown with different inorganic nitrogen sources: nitrate, ammonium, and ammonium nitrate.
- Bleeding sap was collected to analyze total nitrogen, inorganic nitrate-nitrogen, and organic nitrogen content.
- Nitrate reductase activity in leaf extracts was measured and correlated with sap nitrogen levels.
Main Results:
- Sap nitrogen composition varied significantly with the nitrogen source, but not with external nitrate concentration.
- Plants grown with ammonium nitrate exhibited the highest sap nitrogen concentration and fastest growth rates.
- Nitrogen utilization differed: nitrate-fed plants had 60% inorganic nitrate-N and 40% organic-N, while ammonium nitrate-fed plants had 30% inorganic nitrate-N and 70% organic-N. Ammonium-fed plants showed almost entirely organic-N in sap.
- Allantoic acid was the predominant reduced nitrogen compound across all treatments.
- Sap nitrogen concentration in nitrate-fed plants changed dynamically during development, decreasing initially, then increasing upon pod ripening.
- Leaf nitrate reductase activity correlated positively with bleeding sap nitrate content.
Conclusions:
- The form of inorganic nitrogen supplied is a primary determinant of nitrogen partitioning in Phaseolus vulgaris bleeding sap.
- Ammonium nitrate appears to be the most effective nitrogen source for promoting rapid growth and high nitrogen accumulation in this species.
- Nitrate reductase activity is closely linked to the plant's nitrate status, suggesting efficient regulation of nitrate assimilation.
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