Physiological responses of bryophytes Thuidium tamariscinum and Hylocomium splendens to increased nitrogen deposition.
OBJECTIVE
Increased levels of nitrogen (N) deposition lead to enhanced N contents and reduced productivity of many bryophyte species. This study aimed at elucidating the mechanisms by which enhanced N uptake may cause growth reduction of bryophytes, focusing on the effects of N addition on carbon (C) metabolism of bryophytes.


METHODS
Plantlets of Thuidium tamariscinum and Hylocomium splendens were fertilized with NH(4)NO(3) (N load equalling 30 kg ha(-1) year(-1)) for 80 d, including a pulse labelling experiment with (13)CO(2) to dissect the partitioning of carbon in response to N addition.


RESULTS
Growth of T. tamariscinum was not affected by N addition, while H. splendens showed a trend towards growth reduction. Total N concentration was significantly increased by N addition in H. splendens, a significant increase in amino acid-N was found in T. tamariscinum only. In both bryophyte species, a reduction in concentration of lipids, the greatest C storage pool, as well as markedly enhanced turnover rates of C storage pools in fertilized plants were observed.


CONCLUSIONS
The results suggest that growth reduction of H. splendens under high levels of N deposition may be caused by enhanced synthesis of N-containing organic compounds, most probably of cell wall proteins. Disturbance of cellular C metabolism, as indicated by enhanced C pool turnover, may further contribute to the decline in productivity of H. splendens.
Koranda
M
M
Department of Chemical Ecology and Ecosystem Research, University of Vienna, Althanstr. 14, 1090 Vienna, Austria.
Kerschbaum
S
S
Wanek
W
W
Zechmeister
H
H
Richter
A
A
D019068:Bryopsida / Q000254:growth & development / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism; D002247:Carbon Isotopes; D005308:Fertilizers; D009584:Nitrogen / Q000378:metabolism*
D002247:Carbon Isotopes; D005308:Fertilizers; D002244:Carbon; D009584:Nitrogen