Germination, morpho-physiological and biochemical responses of coriander (Coriandrum sativum L.) to zinc excess

A pot experiment was conducted to study the effects of zinc (Zn) on germination, growth, yield, yield components, chlorophyll content, fatty acid composition, total phenol content and fruit essential oil composition of coriander (Coriandrum sativum L.). Application of zinc sulphate (0.1; 1 and 2 mM) in the nutrient solution did not affect the germination, but severely reduced the radicle elongation. In general, there was a decrease in all growth parameters such as plant height, number of secondary branches, diameter of primary and secondary branches, fresh and dry weights of aerial parts and roots. Decrease in seed yield and its components (i.e. number of umbels per primary branches and secondary branches; number of umbel per plant; number of seeds per plant and 1000 seeds weight) were also observed. Zinc treatments reduced the content of total lipids in all plant parts and induced remarkable quantitative changes in fatty acids (FAs) profiles, leading to decrease in their unsaturation, which was indicated by reduction in double bond index (DBI). Exposure to elevated Zn concentrations increased the content of total phenol content in all plant parts. In contrast, Zn excess reduced the yield of essential oil in the fruits and affects negatively the content of oxygenated monoterpenes namely linalool, camphor and geraniol, which were found as the most sensitive compounds. These results are discussed in connection to available data regarding the morpho-physiological and biochemical responses of different plants species to Zn excess and previously tested metals.