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Effect of nodulation, nitrogen fixation and CO 2 enrichment on the physiology, growth and dry mass allocation of seedlings of Alnus rubra Bong.
Author(s) -
AR JOHN A.,
GORDON JOHN C.
Publication year - 1990
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1990.tb00510.x
Subject(s) - nitrogen fixation , dry weight , nitrogenase , photosynthesis , nitrogen , biology , frankia , agronomy , ammonium , horticulture , symbiosis , inoculation , botany , chemistry , root nodule , bacteria , genetics , organic chemistry
SUMMARY Inoculated and uninoculated Alnus rubra Bong, seedlings were grown for 47 days in atmospheres containing ambient (350 μ1 CO 2 1 −1 ) and elevated (650 μl CO 2 1 −1 ) levels of CO 2 , with and without combined nitrogen (20 mg 1 −1 ) supplied as ammonium nitrate. Five plants from each treatment were harvested 15, 30, and 47 days after exposure to CO 2 treatments began. Evidence for the presence of a positive feedback loop between nitrogen fixation and photosynthesis was observed in nodulated plants growing at elevated CO 2 . These plants had greater whole‐plant photosynthesis and nitrogenase activity, leaf area and nitrogen content, as well as nodule and plant dry mass, relative to nodulated plants grown at ambient CO 2 and non‐nodulated plants grown at both CO 2 levels. This feedback may be an important way in which the potential carbon drain of nitrogen fixation on the host plant could be compensated; increased nitrogen availability resulting in stimulated leaf area growth and whole‐plant photosynthesis. The relative amount of dry mass allocated below ground decreased for all seedlings over time, and the amount allocated above ground increased. This shift in allocation occurred slowly and at a constant rate in non‐nodulated plants and more rapidly and abruptly when plants were nodulated. The proportion of dry mass allocated below ground was consistently greater in non‐nodulated plants. Dry mass allocation to the stem was increased when combined nitrogen was applied and was greatest in nodulated plants grown at high CO 2 . Dry mass partitioning among other organs was not directly affected by nodulation, CO 2 enrichment, or other treatment interactions.