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Modeling C and N transport to developing soybean fruits
1Boyce Thompson Institute for Plant Research, Ithaca, New York 14853.
Plant Physiology
|November 1, 1982
Summary
Soybean nitrogen transport differs with nitrogen supply. Ureides dominate in low-nitrogen xylem, while amides and nitrate are key in high-nitrogen xylem, impacting fruit development.
Area of Science:
- Plant Physiology
- Agricultural Science
- Biochemistry
Background:
- Nitrogen (N) is crucial for plant growth, with its transport forms varying based on supply.
- Soybeans (Glycine max) utilize ureides and amides as primary nitrogenous compounds.
- Understanding N transport is vital for optimizing crop yield and nitrogen use efficiency.
Purpose of the Study:
- To investigate the forms of nitrogen transported in xylem and phloem of soybean plants under different nitrogen supplies.
- To quantify the contribution of xylem-to-phloem transfer to nitrogen import in developing soybean fruits.
- To model carbon (C) and nitrogen (N) transport dynamics to soybean fruits.
Main Methods:
- Collection and analysis of xylem sap and phloem exudates from detached soybean leaves and fruit tips.
- Analysis of nitrogenous compounds (ureides, amides, amino acids, nitrate) in exudates.
- Development of a model integrating C:N ratios, fruit growth, and respiration data.
Main Results:
- Ureides were the predominant N form (91%) in xylem of nitrogen-deficient (-N) plants, while amides (45%) and nitrate (23%) dominated in nitrogen-fertilized (+N) plants.
- Phloem from leaves showed amino acids (44%) and ureides (36%) in -N plants, versus amides (63%) in +N plants.
- Fruit tip phloem analysis indicated ureides and amides accounted for the majority of N imported by fruits in both -N and +N treatments.
- Xylem-to-phloem transfer supplied 35% to 52% of fruit nitrogen, with phloem oversupplying N requirements, leading to export of 13% of imported N from fruits.
Conclusions:
- Nitrogen supply significantly alters the forms of N transported in soybean xylem and phloem.
- Phloem appears to oversupply nitrogen to developing fruits, suggesting a regulatory mechanism for N import.
- The study provides insights into C and N partitioning and transport efficiency in developing soybean fruits.
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