Elevated zinc concentrations did not induce thiols in spinach (Spinacia oleracea) and parsley (Petroselinum crispum)

Abstract

AbstractBackgroundPlants evolved various mechanisms to cope with metal stress. Cadmium (Cd) exposure specifically induces the synthesis of thiol‐rich substances such as phytochelatins. Due to the chemical similarity of Cd and zinc (Zn), similar detoxification mechanisms for both metals are under discussion.AimWe conducted a nutrient solution experiment to investigate thiol accumulation of parsley (Petroselinum crispum) and spinach (Spinacia oleracea) cultivars at different metal toxicity levels in vivo.MethodsThree metal treatments were applied: 1 µM Zn (control), 10 µM Zn, and 1 µM Zn + 1 µM Cd. After 10 days, thiol accumulation in parsley and spinach cultivars, which differ in their Zn tissue tolerance, was measured.ResultsSpinach and parsley cultivars differed in metal uptake, translocation, and resistance. In spinach, Cd application induced more severe toxicity symptoms and biomass reduction than Zn. Cadmium toxicity was more pronounced in spinach than in parsley due to higher Cd translocation of spinach cultivars. Despite comparable Zn tissue concentrations, parsley did not show any Zn toxicity symptoms. Due to lower Cd tissue concentrations, only a slight browning of parsley roots was found after Cd treatment. Whereas Cd application induced thiol synthesis in both plant species, Zn excess did not.ConclusionAs elevated Zn concentrations in plant tissues did not induce thiol synthesis, a contribution of phytochelatins to Zn homeostasis and detoxification was excluded.