© 1994 Heron Publishing—Victoria, Canada
Growth and nutrition of small Betula pendula plants at different relative addition rates of manganese
Anders Göransson
Swedish University of Agricultural Sciences, Department of Ecology and Environmental Research, PO Box 7072, S-750 07 Uppsala,
Sweden / Received April 14, 1993
Summary
In a series of experiments, growth of small birch plants (Betula pendula Roth) was controlled by the relative addition rate of manganese, RMn (day–1). The RMn treatments were 0.05, 0.10, 0.15 and 0.20 day–1 with free access to all other nutrients. In an additional treatment, FA, there was free access to all nutrients including
Mn. The pH of the nutrient solution ranged between 3.9 and 4.1, and the conductivity was between 100 and 200 µS cm–1. After an adjustment phase to steady-state growth, there was a one-to-one relationship between the relative growth rate,
RG (day–1), and the supply of manganese, RMn (day–1). The Mn concentration of the plants ranged from 6 to 13 µg gDW–1 in all treatments with limiting RMn and was approximately 200 µg gDW–1 in the FA treatment. At steady-state growth, the plants showed specific Mn deficiency symptoms, including leaf mortality,
that were more pronounced at severe Mn limitation. Total nonstructural carbohydrate concentrations were low, less than 7.5%
of dry weight at Mn limitation, and the fraction of plant dry matter partitioned to roots was much less at Mn limitation than
has previously been reported for equivalent rates of N or P supply. Manganese uptake rate per unit root growth rate, dMn/dWr (µmol gDW–1) was unaffected by the supply of Mn. At Mn limitation, low rates of plant growth were associated with high values of specific
leaf area (37 versus 36 m2 kgDW–1), and lower values of leaf weight ratio (40 versus 61%) and net assimilation rate (3 versus 10 kgDW–1 m–2 day–1) than were found at higher RMn.
Keywords:
biomass, birch, carbon allocation, Mn concentration, nutrition, relative growth rate.
