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Role of nutrient level and defoliation on symbiotic function: experimental evidence by tracing C-14/N-15 exchange in mycorrhizal birch seedlings

Kytöviita, Minna-Maarit LU (2005) In Mycorrhiza 15(1). p.65-70
Abstract
High nutrient availability and defoliation generally reduce ectomycorrhizal colonization levels in trees, but it is not known how this affects the functional aspects of mycorrhizal symbiosis. It was therefore investigated whether (1) defoliation or increasing substrate N availability reduce C allocation from the plant to the fungus and N allocation from the fungus to the plant (symbiotic resource exchange), (2) symbiotic resource exchange depends on relative N and P availability, and (3) fungal N translocation to plant and plant C allocation to fungus are interdependent. Birch (Betula pendula) seedlings were grown in symbiosis with the ectomycorrhizal fungus Paxillus involutus at five times excess N, or at five times excess N and P for 6... (More)
High nutrient availability and defoliation generally reduce ectomycorrhizal colonization levels in trees, but it is not known how this affects the functional aspects of mycorrhizal symbiosis. It was therefore investigated whether (1) defoliation or increasing substrate N availability reduce C allocation from the plant to the fungus and N allocation from the fungus to the plant (symbiotic resource exchange), (2) symbiotic resource exchange depends on relative N and P availability, and (3) fungal N translocation to plant and plant C allocation to fungus are interdependent. Birch (Betula pendula) seedlings were grown in symbiosis with the ectomycorrhizal fungus Paxillus involutus at five times excess N, or at five times excess N and P for 6 weeks. One-half of the plants were defoliated and the plant shoots were allowed to photosynthesize (CO2)-C-14 while the fungal compartment was exposed to (NH4)-N-14. After 3 days, the C-14 of plant origin in fungal tissues and N-15 of fungal origin in plant tissues were quantified. Nutrient availability had no observable effect on symbiotic resource exchange in non-defoliated systems. Defoliation reduced symbiotic N acquisition by plants at all levels of nutrient availability, with the reduction being most marked at higher N availability, indicating an increased tendency in the symbiotic system to discontinue resource exchange after defoliation at higher fertility levels. The concentration of C-14 in extramatrical mycelium correlated significantly with the concentration of N-15 in birch shoots. The results support the assumption that N delivery to the host by the mycorrhizal fungus is dependent on C flow from the plant to the fungus, and that exchanges between the partners are reciprocal. No significant reductions in root C-14 content as a response to defoliation were observed, indicating that defoliation specifically reduced allocation to fungus, but not markedly to roots. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
phosphorus, nitrogen, herbivory, ectomycorrhiza
in
Mycorrhiza
volume
15
issue
1
pages
65 - 70
publisher
Springer
external identifiers
  • wos:000226303000009
  • scopus:12844280723
ISSN
1432-1890
DOI
10.1007/s00572-004-0337-y
language
English
LU publication?
yes
id
442d4ff5-1093-4a5a-941e-eb827e7027e4 (old id 255997)
date added to LUP
2007-08-23 16:47:14
date last changed
2017-05-21 04:16:12
@article{442d4ff5-1093-4a5a-941e-eb827e7027e4,
  abstract     = {High nutrient availability and defoliation generally reduce ectomycorrhizal colonization levels in trees, but it is not known how this affects the functional aspects of mycorrhizal symbiosis. It was therefore investigated whether (1) defoliation or increasing substrate N availability reduce C allocation from the plant to the fungus and N allocation from the fungus to the plant (symbiotic resource exchange), (2) symbiotic resource exchange depends on relative N and P availability, and (3) fungal N translocation to plant and plant C allocation to fungus are interdependent. Birch (Betula pendula) seedlings were grown in symbiosis with the ectomycorrhizal fungus Paxillus involutus at five times excess N, or at five times excess N and P for 6 weeks. One-half of the plants were defoliated and the plant shoots were allowed to photosynthesize (CO2)-C-14 while the fungal compartment was exposed to (NH4)-N-14. After 3 days, the C-14 of plant origin in fungal tissues and N-15 of fungal origin in plant tissues were quantified. Nutrient availability had no observable effect on symbiotic resource exchange in non-defoliated systems. Defoliation reduced symbiotic N acquisition by plants at all levels of nutrient availability, with the reduction being most marked at higher N availability, indicating an increased tendency in the symbiotic system to discontinue resource exchange after defoliation at higher fertility levels. The concentration of C-14 in extramatrical mycelium correlated significantly with the concentration of N-15 in birch shoots. The results support the assumption that N delivery to the host by the mycorrhizal fungus is dependent on C flow from the plant to the fungus, and that exchanges between the partners are reciprocal. No significant reductions in root C-14 content as a response to defoliation were observed, indicating that defoliation specifically reduced allocation to fungus, but not markedly to roots.},
  author       = {Kytöviita, Minna-Maarit},
  issn         = {1432-1890},
  keyword      = {phosphorus,nitrogen,herbivory,ectomycorrhiza},
  language     = {eng},
  number       = {1},
  pages        = {65--70},
  publisher    = {Springer},
  series       = {Mycorrhiza},
  title        = {Role of nutrient level and defoliation on symbiotic function: experimental evidence by tracing C-14/N-15 exchange in mycorrhizal birch seedlings},
  url          = {http://dx.doi.org/10.1007/s00572-004-0337-y},
  volume       = {15},
  year         = {2005},
}