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Uptake and metabolism of nitrate in mycorrhizal plants as affected by water availability and N concentration in soil
Author(s) -
Azcón R.,
Rodríguez R.,
AmoraLazcano E.,
Ambrosano E.
Publication year - 2008
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2007.00962.x
Subject(s) - fertilizer , human fertilization , nitrate reductase , proline , nitrogen , shoot , chemistry , nitrate , agronomy , nitrogen cycle , inoculation , horticulture , biology , amino acid , biochemistry , organic chemistry
Summary We compare the effect of arbuscular mycorrhizal (AM) colonization and PO 4 −3 fertilization on nitrate assimilation, plant growth and proline content in lettuce plants growing under well‐watered (−0.04 MPa) or drought (−0.17 MPa) conditions. We also tested how AM‐colonization and PO 4 −3 fertilization influenced N uptake ( 15 N) and the percentage of N derived from the fertilizer (% NdfF) by plants under a concentration gradient of N in soil. Growth of mycorrhizal plants was comparable with that of P‐fertilized plants only under well‐watered conditions. Shoot nitrogen content, proline and nitrate reductase activity were greater in AM than in P‐fertilized plants under drought. The addition of 100 μ g g −1 P to the soil did not replace the AM effect under drought. Under well‐watered conditions, AM plants showed similar (at 3 mmol N), greater (at 6 mmol N) or lesser (at 9 mmol N) %NdfF than P‐fertilized plants. Comparing a control (without AM inoculation) to AM plants, differences in % NdfF ranged from 138% (3 mmol N) to 22.6% (6 mmol N) whereas no differences were found at 9 mmol N. In comparison with P fertilization, mycorrhizal effects on %NdfF were only evident at the lowest N levels, which indicated a regulatory mechanism for N uptake in AM plants affected by N availability in the soil. At the highest N level, P‐fertilized plants showed the greatest %NdfF. In conclusion, AM symbiosis is important for N acquisition and N fertilizer utilization but this beneficial mycorrhizal effect on N nutrition is reduced under large quantities of N fertilizer.