The castor oil plants were harvested 74 days after sowing, and the
shoots were separated from the roots at harvest. The shoots were washed
with tap water followed by washing with a solution of 1% HCl and distilled
water. Roots were sieved, washed and soaked for 90 min in a solution of
0.02 mmol L−1 EDTA (disodium salt). After soaking, the roots were
washed again with distilled water. Plant samples were washed, dried,
weighed and then digested using HNO3/H2O2 in a microwave oven
prior to the elemental/nutritional analysis.