β Scribed by Singer, Catherine E. ;Havill, D. C.
No coin nor oath required. For personal study only.
The plant available manganese concentration (Mn 2+) of salt-marsh sediments was compared to that of acidic and neutral soils. The mean soil-manganese concentration was higher in the top 1 cm of salt-marsh soil than in the neutral soil and comparable to that of the acidic soil (0-5 cm). A peak in the soil-manganese concentration in the upper marsh was observed one week after the springtide but this effect was not evident in the lower marsh. Despite these differences, there was no correlation between mean manganese concentration and position on the marsh.
The response to manganese of salt-marsh halophytes was studied by measuring growth and root elongation in a range of Mn 2+ concentrations with and without sodium chloride. Although there was a differential response to manganese between salt-marsh species, manganese resistance was not related to position on the marsh. Most of the species investigated were tolerant of Mn 2+ at concentrations higher than normally recommended for plant growth. Moreover a salt-marsh ecotype ofFestuca rubra was found to have a higher manganese resistance than an inland ecotype of the same species.
When sodium chloride was included in the growth medium, salt-marsh plants had a greatly increased resistance to manganese associated with a reduced uptake. This effect is reflected in the tissue-manganese concentration which was lower than in Deschampsiaflexuosa although both groups of plants were exposed to a similar range of Mn 2+ concentrations. It is concluded that sodium chloride markedly reduces the phytotoxicity of manganese in salt marshes.
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