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THE BIOSYNTHESIS OF C COMPOUNDS : I. THE BIOSYNTHESIS OF C-LABELED STARCH
1Lankenau Hospital Research Institute, Philadelphia.
The Journal of General Physiology
|October 30, 2009
Summary
Bean leaves convert carbon dioxide (CO2) into starch, with 67% of the utilized carbon-13 (C13) found in starch. Soluble carbohydrates contained 23% of the C13, and the rest was in coarse tissue fragments.
Area of Science:
- Plant Physiology
- Biochemistry
- Isotope Tracing
Background:
- Photosynthesis is the primary process by which plants convert carbon dioxide into organic compounds.
- Understanding the distribution of fixed carbon within plant tissues is crucial for comprehending metabolic pathways.
Purpose of the Study:
- To quantify the distribution of carbon-13 (C13) in different fractions of bean leaves after C13O2 assimilation.
- To determine the proportion of C13 incorporated into starch and soluble carbohydrates.
Main Methods:
- Bean leaves were exposed to C13-enriched carbon dioxide (C13O2).
- Isotopic analysis was performed on extracted starch, soluble carbohydrates, and coarse tissue fragments.
- Quantification of C13 excess in each fraction was determined using mass spectrometry.
Main Results:
- Starch isolated from mesophyll cells showed a C13 excess of 7.05 atom per cent, accounting for approximately 67% of the total C13 uptake.
- Soluble carbohydrates contained 6.72 atom per cent C13 excess, representing about 23% of the assimilated C13.
- The remaining C13 (9.73%) was found in the coarse tissue fragments fraction.
Conclusions:
- Starch is a major sink for newly assimilated carbon in bean leaves.
- The distribution of C13 indicates preferential allocation to starch synthesis during photosynthesis.
- The experimental setup and procedures are detailed for reproducibility.
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