At harvest, leaf samples were dried in an oven for 48 h and
grinded into fine powder. Approximately 1 g of the powder was
weighed out in a crucible and added with 4–5 ml of 50% ethanol.
The samples were ashed at 500 ◦C in an electricmuffle furnace (Controller
B180, Nabertherm GmbH, Lilienthal/Bremen, Germany) for
8 h.