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Implications of N acquisition from atmospheric NH 3 for acid‐bAse and cation‐anion balance of Lolium perenne
Author(s) -
Wollenweber B.,
Raven J. A.
Publication year - 1993
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 - 10.1111/j.1399-3054.1993.tb05208.x
Subject(s) - shoot , lolium perenne , ammonia , chemistry , dissolution , ammonium , organic acid , environmental chemistry , botany , poaceae , biochemistry , biology , organic chemistry
In the atmosphere, ammonia (NH 3 ) is the third most abundant N species which, due to various natural and anthropogenic sources, can locally reach high concentrations. The acquisition of atmospheric NH 3 by plant shoots will lead to two opposing effects on acid‐base balance. Absorption and dissolution of NH 3 will cause an alkalinisation, while the assimilation of NH 3 results in an acidification. Different rates of these processes would lead to an acid‐base imbalance with consequences for the ionic balance of the plant. As there is only a limited capacity for biochemical disposal of excess H + in shoots, pH regulation may involve a pattern of (in)organic ion flow between shoots and roots followed by H + /OH − extrusion into the media via roots. The acquisition of NH 3 as additional N source should lead to a reduction in the ratio of mol H + /OH − gained per mol N assimilated. We have recently investigated the NH 3 acquisition by Lolium perenne L. cv. Centurion and studied the effects of gas phase NH 3 on growth, acid‐base balance and water‐use efficiency. The experiments, therefore, included the application of a range of 14 NH 3 to the shoots and of 15 N as NO 3 − , NH 4 + or NH 4 NO 3 to the roots. After a summary of the main conclusions from those experiments, we discuss the implications of the use of atmospheric NH 3 for the mineral composition of the plants. Over the range of NH 3 supplied, plants from all treatments could utilize gas‐phase NH 3 . Plants receiving NO 3 − via their roots had a higher capacity to use gaseous NH 3 than those growing with NH 4 + . NH 3 assimilation in shoots reduced both the acid load with NH 4 + nutrition and the alkaline load with NO 3 − supply to the roots. The most significant effect of fumigation on the ion balance was an increase in K + within all treatments, and this effect was highest in the NH 4 + ‐fed plants. The results of the experiments support predictions of a combination of neutralizing biochemical reactions as well as transport of organic anion salts between shoots and roots as possible acid‐base regulation mechanisms of the whole plant.