Growth phenotype analysis
Seeds were sterilized with 30% bleach for 10 min, followed by washing 5 times with sterile water. Plants were grown for 5 d on half-strength MS media, after which they were transferred to agar plates with indicated nutrients for 7 d. They were grown 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. Plates were scanned, after which primary root length (primary root growth after the 7 d treatment) was measured from the resulting images in ImageJ (version 1.50b). Plants of the same genotype from one plate (3-6 plants) were pooled and weighed to determine seedlings fresh weight. All experiments were performed with three biological replicates. For the growth response of adult plants to high Mg2+ concentration in growth medium, wt and pldα1-1 were grown hydroponically for 3 weeks in modified half-strength Hoagland´s media (Hoagland & Arnon, 1950) followed by 10 d in media with or without 10 mM MgSO4. Nutrient concentrations were as follows: NH4H2PO4, KNO3, Ca(NO3)2.4H2O, MgSO4.7H2O, 24.5 µM ferric citrate, 0.45 µM KI, 4.85 µM H3BO3, 5.92 µM MnSO4.4H2O, 0.7 µM ZnSO4.7H2O, 0.1 µM Na2MoO4.2H2O, 0.01 µM CuSO4.5H2O, 0.01 µM CoCl2.6H2O, 10.02 µM Na2EDTA, 10 µM FeSO4.7H2O, 55.51 µM myo-inositol, 0.81 µM nicotinic acid, 0.49 µM pyridoxin, and 2.97 µM thiamin. Aeration of the hydroponic media was performed every 3 h for 15 min using an aquarium air pump. Nutrient solution was replaced once weekly. Plants were grown in a growth chamber at 22°C during the day, 21 °C at night, under short-day conditions (10 h light per day).