In this study, basil (Ocimum basilicum L.) seedlings were intoxicated with Cd2+ and cultivated using a 5% v v–1 Hoagland nutrient solution. Desorption electrospray ionization mass spectrometry imaging (DESI-MSI) was used to identify different compounds on basil leaves (without and with 10 μmol L–1 Cd2+). DESI-MSI analysis identified 28 images of ions with high accuracy (mass deviation < 1.8 ppm) in contaminated and uncontaminated leaves. The biomarkers formed due to Cd external stress under controlled laboratory experiments were putatively identified in contaminated leaves as jasmone, hexose sugars, salvigenin, flavonoids (C18H14O7 and C21H22O10), and fatty acyl glycosides (C18H28O9). The accumulation of Cd occurred preferentially in the roots but also on the stems and leaves. The methodology to quantify Cd in basil organs was optimized and validated using an ultrasound-assisted micro-extraction procedure. Limits of detection and quantification were 6 and 17 μg L–1, respectively, with a precision better than 7.5 %, obtained by fast sequential flame atomic absorption spectrometry (FS FAAS). The standard reference material of spinach leaf (SRM NIST 1570a) presented a recovery of 101 ± 8 %. DESI-MSI was for the first time employed to examine the behavior of metabolites in plants maintained under stress conditions by the exposure to high levels of cadmium.

The ionomic response of basil leaves, stems, and roots to Cd2+ was evaluated in seedlings grown in a hydroponic system for 15 days. Ions were quantified by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Cd accumulated mainly in roots while Be, Li, Ca, Mg and Sr in leaves and K and Mn in stems. Compared to the control group, basil seedlings treated with Cd2+ accumulated higher Ca, Cu, Mn, Sr, and Zn contents in roots, even when exposed at low levels. Pearson positive correlations between Cd and essential and nonessential elements were mostly observed in leaves and roots (p &lt; 0.05). On the other hand, negative correlations were observed mainly in stems with all elements, except Ba, Li, Sr, and Zn. Principal component analysis (PCA) showed an ionomic discrimination between leaves, stems, and roots, with Cd strongly correlated to Zn, Cu and Sr.