Measurement of nutrient content
Seedlings were grown for 7 d on half-strength MS media, after which they were transferred to agar plates with indicated nutrients for 10 d. Plates were kept in a growth chamber at 22°C during the day, 21°C at night, under long day (16 h of light) conditions at 100 μmol m−2 s−1. Mg2+-, K+-, and Ca- content in samples (pooled plants, ~100 mg dry weight) was determined with inductively coupled plasma optical emission spectroscopy (Spectroblue, Spectro, Germany) analysis in the laboratory of Ekolab Žamberk, Czech Republic).