Nitrogen Source and the Tolerance of Deschampsia Flexuosa, Holcus Lanatus and Bromus Erectus to Aluminium During Seedling Growth

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Abstract
The growth of 3 grasses whose natural distribution ranged from acidic to calcareous soils was measured in response to the concentration of 2 major pH-linked soil chemical factors, N and Al, supplied in flowing culture. All 3 spp. showed one or more of the basic responses proposed in 4 hypotheses based on their ecological distribution. D. flexuosa grew equally fast with either NO3-N or NH4-N as the N source. It was tolerant of any combination of N source and Al except for the highest concentration of Al (5.4 mg l-1) supplied with NO3-N. H. lanatus grew significantly faster in NO3-N than it did in NH4-N and showed classical symptoms of Al toxicity in the presence of NO3-N. The strongly adverse effect of NH4-N was significantly ameliorated by the addition of Al. B. erectus also grew significantly faster in NO3-N than it did in NH4-N and was susceptible to Al toxicity in the presence of NO3-N. The very small extent of growth in NH4-N masked any possible effects of Al and growth was not increased in the presence of Al. A revision of ideas on the roles of inorganic toxins in acidic soils is proposed.

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