Wet ashing of plant tissue
Samples (0.5 g) of dried ground plant material were weighed into 100-ml Kjeldahl flasks containing a glass bead. The samples were predigested with 5 ml of HNO3, cooled, and digested to fumes of HC1O4 after adding 5 ml of a mixture of HNO3 and HC1O4 (3 + 1) according to the method reported by Leggett and Westermann (1973). After digestion, about 40 ml of distilled demineralized water was added to each flask and the contents were brought to near boiling to ensure complete dissolution of sample except for silica. Samples were cooled, diluted to 50 ml, and filtered.