Manganese and calcium nutrition of Pinus sylvestris and Pinus nigra from two different origins I. Manganese

Seedlings of Pinus sylvestris L. grown from seed of Creek and British origi ns, and of Pinus nigra Arnold grown from seed of Creek black pine (Pinus ni gra var. nigricans Host.) and of Corsican pine (Pinus nigra var, maritima ( Ait.) Melv.) collected in Britain were used in determining the response to both increasing levels of Mn supply in nutrient solution and to varying rat es of Mn and Ca supply. Plants were about 27 weeks old when harvested. Unde r the conditions used it proved impossible to induce mean foliar Mn concent ration below about 70 p.p.m. but even at this some plants showed symptoms o f-deficiency. Maximum growth of P. sylvestris occurred at foliar Mn concent rations of 240 p.p.m, and 280 p.p.m, for the plants of Creek and British or igins respectively, the ranges over which growth was 90 per cent of maximum being 84-855 and 77-1450 p.p.m. The British origins were more tolerant of high Mn supply and high tissue concentrations of Mn than were the Creek der ived plants. No significant depression of growth of P. nigra was induced at low rates of supply but upper optimum limits were identified at foliar Mn concentrations of 2100 and 1400 p.p.m. for the Creek and British sourced pl ants. Increasing Ca supply depressed Mn uptake but did not alter optimum fo liar Mn concentrations.