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Root ammonium transport efficiency as a determinant in forest colonization patterns: an hypothesis
Author(s) -
Kronzucker H. J.,
Siddiqi M. Y.,
Glass A. D. M.,
Britto D. T.
Publication year - 2003
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2003.00032.x
Subject(s) - ecological succession , seral community , ammonium , biology , colonization , botany , nitrate , salicaceae , ecology , chemistry , woody plant , organic chemistry
Ratios of ammonium (NH 4 + ) to nitrate (NO 3 – ) in soils are known to increase during forest succession. Using evidence from several previous studies, we hypothesize that a malfunction in NH 4 + transport at the membrane level might limit the persistence of early successional tree species in later seral stages. In those studies, 13 N radiotracing was used to determine unidirectional fluxes and pool sizes of NH 4 + and NO 3 – in seedlings of the late‐successional species white spruce ( Picea glauca ) and in the early successional species Douglas‐fir ( Pseudotsuga menziesii var. glauca ) and trembling aspen ( Populus tremuloides ). At high external NH 4 + , the two early successional species accumulated excessive NH 4 + in the root cytosol, and exhibited high‐velocity, low‐efficiency (15% to 22%), membrane fluxes of NH 4 + . In sharp contrast, white spruce had low cytosolic NH 4 + accumulation, and lower‐velocity but much higher‐efficiency (65%), NH 4 + fluxes. Because these divergent responses parallel known differences in tolerance and toxicity to NH 4 + amongst these species, we propose that they constitute a significant driving force in forest succession, complementing the discrimination against NO 3 – documented in white spruce (Kronzucker et al. 1997).