The Dual Function of Lysine as Iron-Chelator and Active Compound Benefits Productivity and Drought Tolerance of Nigella sativa L

Drought stress is affecting crop production worldwide. One promising strategy to reduce the negative effect of drought stress is the foliar application of micronutrients, such as zinc or iron. However, the uptake efficiency over the leaf surface depends on nutrient solubility. In this study the effect of inorganic iron FeSO₄ and lysine-chelated iron (Fe-Lys) on productivity and drought tolerance of Nigella sativa L. (Nigella or black cumin) was compared. Moreover, the role of lysine itself was investigated. Spraying leaves with Fe-Lys improved growth and yield under control and drought stress conditions, while FeSO₄ had only minor effects. Surprisingly, plants on which only lysine was applied showed many of the improvements of Fe-Lys application, including increased activity of antioxidative enzymes and ion levels. Our results suggest that foliar Fe-Lys application is a promising approach to minimize drought stress effects in Nigella. Moreover, they point to an important function of lysine in drought stress tolerance. The molecular mechanism, further steps to improve the approach and the result’s relevance for other plant species are discussed.