Exogenous Melatonin Affects the Morphometric Characteristics and Glucosinolates during the Initial Growth Stages of Broccoli

Nowadays, there is a global surge in interest surrounding novel foods, particularly sprouts, microgreens, and baby leaves, attributed to their rich content of bioactive compounds, such as phenolic derivatives, glucosinolates, and vitamins. This study delves into the impact of exogenously applied melatonin on novel foods derived from Brassica oleracea L. Two distinct cultivars of broccoli (Brassica oleracea var. italica Plenck), namely Sicilian sprouting broccoli (Broccolo nero) and a commercial variety (Cavolo Broccolo Ramoso Calabrese), were compared across the sprouts, microgreens, and baby leaves stages, adhering to organic farming practices. Various doses of melatonin (0, 50, and 100 µM) were administered at each harvesting stage. Plantlets were collected at different growth stages and assessed for key morphometric traits, including the weight, hypocotyl length, and cotyledon dimensions during the sprouts stage. For microgreens, the number and dimensions of the true leaves were recorded, while for baby leaves, the stem length was additionally measured. The analysis of glucosinolates was carried out using a high-performance liquid chromatograph with a diode array detector (HPLC-DAD). The results revealed significant variations among the experimental factors considered. Melatonin application significantly influenced the morphometric parameters at different growth stages, exhibiting notable variations in the weight, hypocotyl length, cotyledon width, and leaf width. The GLSs profile exhibited significant variations between the different growth stages and genotypes studied. Particularly noteworthy was the tendency for the GLSs content to be higher during the sprouts stage compared to the baby leaves stage, ranging from 24.07 to 4.61 µmol g−1 d.w. from sprouts to baby leaves, respectively.