The effectiveness of synthetic zinc(Zn)-amino chelates in supplying Zn and alleviating salt-induced damages on hydroponically grown lettuce

• [Zn(Gly)2] was more effective than Zn-sulfate in supplying Zn for lettuce.
• [Zn(Gly)2] was more effective in reducing Na and enhancing K and Ca in salt-exposed lettuce.
• [Zn(Gly)2] reduced lipid peroxidation and enhanced crop tolerance to salt stress.
• [Zn(Gly)2] is recommended as Zn source for hydroponically-grown lettuce particularly under saline condition.

In this study, three zinc(Zn)-amino chelates i.e., Zn-arginine [Zn(Arg)2], Zn-glycine [Zn(Gly)2], and Zn-gluthamine [Zn(Gln)2] were synthesized and their effects on yield and nutrient elements uptake by lettuce (Lactuca sativa L. cv. Lollo Rossa) grown in nutrient solution containing 0, 20, and 40 mM NaCl were compared with a commercial ZnSO4. Zinc nutrition could partly alleviate the damages induced by salinity on root and shoot growth of lettuce; although this effect was dependent on the applied Zn source. At saline conditions, the [Zn(Gly)2] was more effective than the other Zn sources to improve root and shoot growth of lettuce. Concentration of malondialdehyde (MDA) in the roots was increased by salt stress. In contrast, addition of Zn resulted in lower production of MDA. The [Zn(Gly)2] was more effective than the other Zn sources in reducing MDA content. Addition of Zn significantly decreased sodium (Na) and increased potassium (K) concentration in the root and shoots of lettuce plants exposed to salinity. In addition, lettuce plants supplied with Zn accumulated higher calcium (Ca), Zn, and iron (Fe) in their tissues compared with those at the Zn free nutrient solution. The highest increase in Fe and Ca concentration was achieved by [Zn(Gly)2] while [Zn(Gln)2] and [Zn(Arg)2] resulted in the highest K concentration in roots and shoots of lettuce. According to the results obtained, the [Zn(Gly)2] was more effective than Zn-sulfate in supplying Zn and alleviating salt-induced damages on hydroponically grown lettuce.