Zinc Biofortification of the Edible Cactus Nopalea cochenillifera Grown Under Hydroponic Conditions

We investigated the effects of zinc (Zn) supplementation on the growth and Zn accumulation of the edible cactus Nopalea cochenillifera (L.) Salm-Dyck by exposing hydroponically grown cladodes of N. cochenillifera to 0 ppm, 50 ppm, or 200 ppm of Zn for 10 weeks and assessing their growth. Daughter cladodes emerged from the mother cladodes and continued to grow at all three concentrations of Zn but growth of the daughter cladodes was inhibited and the fresh weights of both the daughter and mother cladodes were lower with the 200 ppm treatment. A high Zn concentration in the nutrient solution greatly increased the Zn concentration in the plant parts, with the roots of plants that were treated with 50 ppm and 200 ppm surpassing the threshold levels of Zn hyperaccumulator plants. A larger amount of Zn accumulated in the daughter cladodes with the 50 ppm treatment than with the 200 ppm treatment but there was no significant difference between these treatments in the other plant parts. These results suggest that the supplementation of nutrient solution with Zn affects the growth of N. cochenillifera and that this plant has a high capacity for accumulating Zn.