Effects of foliar applied asparagine, glycine and citric acid on cadmium uptake and yield in wheat

Cadmium (Cd) contamination is an important heavy metal that threatens agricultural production and food safety. This study investigates the potential of foliar applications of asparagine (Asn), glycine (Gly) and citric acid (CA) to reduce Cd uptake and improve the nutrient balance of wheat (<i>Triticum durum</i> L.). A pot experiment was conducted under controlled conditions with three different Cd concentrations (0, 3 and 12 mg Cd kg^-1 soil). The mixture containing 0.5 mMg Gly, Asn, and CA was applied to the leaves a total of five times at 5-day intervals during the tillering, stem elongation, heading and flowering periods of wheat, starting 39 days after planting. The analysis showed that the application of Asn reduced the Cd concentration in the grains by 14.82%, 31.08% and 16.66%, respectively, while the application of Gly resulted in a reduction of 37.78%, 16.41% and 12.79% and the application of CA resulted in a reduction of 34.78%, 36.25% and -1.60% compared to the control (C0) group. In addition, grain yield increased in response to the amino acid applications, with Asn improving yield by 6.10%, 9.95% and 5.90%; glycine by 3.86%, 7.59% and 9.34%; CA by -2.64%, 6.16% and 3.44%, respectively. These amino acid treatments alleviated the growth limitations caused by Cd stress by increasing the grain yield of wheat. However, the effect of CA on Cd detoxification was lower compared to the amino acids. The results show that Asn and Gly not only reduce Cd accumulation in wheat but also improve nutrient balance and increase yield. Consequently, foliar application of these amino acids is a promising strategy to improve plant safety in Cd-contaminated agricultural soils.