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Release of carbon and nitrogen compounds by plant roots and their possible ecological importance +
Author(s) -
Merbach Wolfgang,
Mirus Edith,
Knof Günther,
Remus Rainer,
Ruppel Silke,
Russow Rolf,
Gransee Andreas,
Schulze Joachim
Publication year - 1999
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/(sici)1522-2624(199908)162:4<373::aid-jpln373>3.0.co;2-#
Subject(s) - nitrogen , carbon fibers , chemistry , environmental chemistry , ecology , botany , environmental science , biology , mathematics , organic chemistry , algorithm , composite number
The root‐borne C‐ and N‐flux in the plant/soil system was studied by determining the 14 C‐ or 15 N‐balances in pot trials with soil as a substrate ( 14 CO 2 ‐ or 15 NH 3 ‐application to the shoots, comparison of sterile and nonsterile treatments for quantification of root‐borne substances). The following results were obtained: 1. The amount of (primary) root‐borne carbon compounds released into soil was (besides root respiration) 11—20% of net‐CO 2 ‐assimilation or 13—32% of the 14 C incorporated into the plants (= 1 t C · ha —1 ). 5—6% of 15 N assimilated by the plants were released as root‐borne N compounds (= 15 kg N · ha —1 ). 2. A considerable portion of the root‐borne C (about 6% = 600 kg C · ha —1 ) was found in the rooted soil zone at the end of the experiments (rhizodeposition). 3. (Primary) root‐borne C and N compounds found in immediate vicinity of the roots (about 60—80%) were mainly water soluble, whereas most of the C and N compounds found in a greater distance were water insoluble. The water soluble exudates consisted mainly of neutral (carbohydrates) and acid fractions (organic acids). The basic fraction (amino acids) made up a small portion only. 4. The root‐borne C and N compounds influenced the nutrient balance of soil and plant directly and/or indirectly via microbes (depending on species, variety and nutritional status of plants). 5. Microbes stimulated the release of C‐ and N‐compounds, but rapidly respired 65—85% of the root‐borne C‐compounds, thereby putting a burden on the C‐budget of the “host” plant. 6. It could be shown by the example of hup + Rhizobium meliloti strains (tested by 3 H 2 ‐incorporation) and the wheat‐ Serratia ‐association, that energy efficient microbenplant systems can improve plant performance.