2.4 Plant tissue nutrient analysis
Dried leaves were milled (Retsch MM 400, Retsch GmbH and Co. KG, Haan,
Germany) and passed through a 1 mm sieve. Leaf P concentration was
measured using the molybdate/stannous chloride method (John, 1970; Bao,
2000) after digesting a ~0.1 g sample in
H2SO4-H2O2.
Leaf N and carbon concentrations were determined using an elemental
analyzer NA1500 (Carlo Erba, Thermo Fisher Scientific, Waltham, MA, USA)
and leaf K concentration was determined by the atomic absorption method
(Bao, 2000). All concentrations were calculated on a dry mass basis.