All dried shoot or grain samples were ground to fine
powders in an agate vibrating cup mill (Pulverisette 9;
Fritsch GmbH; Germany). Ground samples (~0.2 g)
were digested in a closed-vessel microwave system
(MarsExpress; CEM Corp; Matthews, NC, USA) with
2 ml of 30%H2O2 and 5 ml of 65%HNO3