Performance of three cardoon cultivars in an industrial heavy metal-contaminated soil: effects on morphology, cytology and photosynthesis

In the present work the cytomorphological and physiological effects on three cardoon cultivars – Sardo, Siciliano, Spagnolo - grown in a metal-polluted soil, were investigated, to assess the traits concurring to the high tolerance to metal stress observed in cv. Spagnolo compared to the other two cultivars. The plants were grown for one month on a real polluted soil collected at a dismantling battery plant, highly enriched by heavy metals, especially Cd and Pb, and their leaves were analyzed by a multidisciplinary approach. TEM observations highlighted severe ultrastructural damage in Sardo and Siciliano, and preserved cytological traits in Spagnolo. Both pigment content and photochemistry indicated a decline in photosynthesis in Sardo and Sicilano and a substantial stability of the same parameters in Spagnolo. Protein analysis indicated a decrease in D1 level in all cultivars; in Spagnolo the D1 decrease was more pronounced and associated to a significant increase in Rubisco, a pattern likely preserving photosynthetic efficiency and high biomass production. In conclusion, Spagnolo cardoon was able to face metal stress through a prompt, multiple response balancing structural and functional traits.