Evaluation location: Oklahoma, United States
Medicago truncatula seeds were surface sterilized, imbibed, and then cold treated by placing on moist filter paper in a Petri dish and incubating for at least 48 h at 4? C. Seeds were germinated in the dark at 24?C for 24 h. Seedlings were transferred to hydroponics and grown under an 18-h-light/6-h-dark regime at a constant temperature of 23?C. The light intensity was 260 uE?m-2?s-1. Twenty seedlings of each accession were used for each treatment: a modified Blaydes medium (Blaydes, 1966) plus Al, and a modified Blaydes medium minus Al. Media were aerated with a small aquarium air pump for 15 min, once per h. The Blaydes medium was modified to contain 0.5 mM CaCl2, 1.8 mM KNO3, 1.8 mM NH4NO3, 30.4 uM MgSO4 ?7 H2O, 22 uM KH2PO4, 13 uM FeSO4, 31.7 uM Ca(NO3)2, 66 uM KCl, 26 uM NaCl, 26 uM H3BO3, 26 uM MnSO4?H20, 5.2 uM ZnSO4?7 H2O, and 4.8 uM KI. Media was maintained at pH 4.3. After five d of growth in hydroponics, seedlings were removed and measured from the base of the cotyledon to the root tip. The experiment was repeated three times, once with the Al concentration at 25 uM as AlCl3 and twice at 50uM AlCl3. Relative root growth, the ratio of seedling root length grown without Al to seedling root length grown with Al, was used as a measure of Al tolerance.
Click for more information on Materials, Methods and data in a .DOC file. Click for an Excel file with root length of the control, stressed and relative along with P-value.