Morphology, physiology, and biochemistry of zinc-stressed caraway plants.

A greenhouse pot experiment was conducted to evaluate the impact of zinc supply (0, 1, and 2 mM Zn as ZnSO4) on morpho-physiological and biochemical parameters of caraway (Carum carvi L.). Exposure to different Zn concentrations for 12 weeks compromised severely all growth parameters (plant height, number of secondary branches, diameter of primary and secondary branches, fresh and dry weight of aerial parts and roots) yield and its components (number of umbels per primary branches and secondary branches; number of umbel per plant; number of seeds per plant; and the weight of 1000 seeds). These manifestations were intimately linked with excessive accumulation of Zn in roots and leaves, alteration of the content of photosynthetic pigments, and extended lipid peroxidation. A manifest increment of proline and soluble sugar content was also observed in response to Zn application. Lipid content in seeds was dropped in Zn-treated plants and the fatty acid profiles were profoundly affected as they were enriched with saturated fatty acids at the expense of unsaturated ones. While improving their oxidative stability as revealed by the reduced values calculated oxidizability and oxidative susceptibility, Zn treatment reduced the lipid nutritional quality of caraway seeds. Moreover, Zn treatment reduced the essential oil yield and its main component carvone while it enhanced the content of its precursor limonene. It also induced alteration of terpene metabolism as revealed in the redirection of the carbon flux to the shikimate/phenylpropanoid pathway resulting in the stimulation of the production of phenolic compounds and their subsequent antioxidant activities.

Responses of Nigella sativa L. to Zinc Excess: Focus on Germination, Growth, Yield and Yield Components, Lipid and Terpene Metabolism, and Total Phenolics and Antioxidant Activities.

A comprehensive analysis of the responses of Nigella sativa L. to elevated zinc concentrations was assessed in pot experiments. Zn excess supply did not affect the germination but drastically reduced radicle elongation. A concentration-dependent reduction in all growth parameters, yield, and yield components was observed. With the increasing Zn concentrations, total lipid contents decreased and changes in fatty composition toward the production of saturated ones were underscored. Despite the reduction in the seeds essential oil yield, a redirection of the terpene metabolism toward the synthesis of oxygenated compounds has been evidenced. A significant increase in the total phenols and flavonoids contents concomitant with improved antioxidant activities has also been found. Collectively, these results highlight the possible use of N. sativa L. in phytoremediation applications, on the one hand, and that Zn excess could represent an excellent alternative to improve the nutritional attributes of this important species, on the other hand.