Impact of different photoperiodic treatments on Spinoso Sardo globe artichoke (Cynara cardunculus L. var. scolymus Fiori) head traits and elementary composition

Globe artichoke is an important crop native to the Mediterranean Basin. Spinoso Sardo (Cynara cardunculus L. var. scolymus Fiori) is a widespread Sardinian cultivar that strongly contributes to the agricultural economy of Italy. In this research, Spinoso Sardo was cultivated under natural (control) or extended (15 and 17 h) photoperiods. The effect of day length on few morphological traits, harvest time, elemental composition was evaluated. Head morphology was little influenced by photoperiod, whereas significant differences were observed in peduncle diameter, showing larger values in natural conditions compared to the other day lengths. The harvest time, expressed as days after emergence, display difference among treatments with highest value for natural condition (193 days) and the lowest value for the 17-h day length. The difference in elementary compositions based on C, N and C/N was evaluated in capitula, stem and leaves (leaves of rosette and peduncle). C content did not show any differences among treatments and among organs, while N and C/N were significantly affected by the day lengths. The maximum N % was found in leaves under 15 h photoperiod (3.6%), while the lowest score was detected in floral stem under control conditions (1.5%). The highest C/N was found in capitula under control conditions (72.5), while the lowest value was found in leaves under 15-h photoperiod (10.8). Total protein content based on the N% is significantly affected by the plant organ (P<0.0001), photoperiod (P=0.0084) and the interaction between these two factors (0.0068). These results showed that the day length deeply influenced the Spinoso Sardo morphological and elemental structure and composition.