The Effects of Aluminium on the Growth of White Clover dependent upon Fixation of Atmospheric Nitrogen

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Abstract
Jarvis, S. C. and Hatch, D. J. 1985. The effects of aluminium on the growth of white clover dependent upon fixation of atmospheric nitrogen.−J. exp. Bot. 36: 1075–1086. The effects of aluminium (Al3 +) on the growth of white clover dependent upon symbiotic fixation of atmospheric nitrogen were examined at concentrations that may be encountered in solutions from soils of low pH. Well established plants were grown in flowing solution culture with carefully maintained concentrations of Al and of P and with pH held constant at a value (4.5) at which insoluble precipitates are unlikely to form. After 3 weeks of treatment, there were major visual differences between treatments in both shoots and roots. Although added Al at 25, 50 and 100 mmol m−3 reduced dry weight, the differences between the plants were not significant. There were, however, some considerable differences in P and Ca contents between the treatments. Much of the Al held by the roots was displaced when plants were transferred to solutions containing either scandium or gallium. As well as the effects on the plant, Al had a considerable influence on the fixation of atmospheric nitrogen. At concentrations of 50 and 100 mmol m−3 Al3+ nodule initiation was reduced and there was a much reduced nodule nitrogenase activity per unit of root. Even at 25 mmol m−3 Al3+, when nodule numbers were not reduced, nitrogenase activity was adversely affected.