Phytoremediation ability of three succulent ornamental plants; cactus (Opuntia humifusa), kalanchoe (Kalanchoe blossfeldiana) and bryophyllum (Bryophyllum delagoensis) under heavy metals pollution

The current status of environmental pollution by heavy metals (HMs) will affect the entire ecosystem components. The results obtained so far indicate that some plants can be effective in removing toxic metals from the soil. For this purpose, the phytoremediation ability of three fleshy ornamental plants; cactus (Opuntia humifusa), kalanchoe (Kalanchoe blossfeldiana) and bryophyllum (Bryophyllum delagoensis), was evaluated under the stress of HMs. These succulents are known for their remarkable adaptive capabilities, allowing them to thrive in harsh environmental conditions, including those with high levels of contaminants. Their robust nature, efficient water-use strategies, and proven potential for heavy metal accumulation made them viable candidates for investigating their phytoremediation potential. This experiment was performed as factorial based on completely randomized block design with two factors; the first factor included the type of plant in 3 levels (cactus, kalanchoe and bryophyllum) and the second one included the type of metal in 5 levels (control, silver, cadmium, lead and nickel) in 3 repetitions. The concentration of each salt used was 100 ppm. The measured parameters included stem height, relative growth, diameter, dry matter percentage of root and shoot, chlorophyll a, b and total chlorophyll, carotenoid, anthocyanin, proline, and elements of nickel, silver, lead and cadmium, as well biological concentration factor. The results showed that the highest amount of final stem height, relative growth, dry matter percentage of shoot and the highest amount of chlorophyll a and b, carotenoid and anthocyanin were obtained in bryophyllum. Also, the results of mean comparison of the data related to the effect of metal type on the plants showed that the highest amount of carotenoid, anthocyanin and biological concentration factor were induced by cadmium. On the other hand, the highest and lowest amount of proline as well anthocyanin and proline were induced by silver and lead, respectively. Totally, bryophyllum had a high resistance to HMs and the examined HMs had less effect on the growth of this plant. Cactus, among trial species, exhibited superior potential for HM absorption compared to kalanchoe and bryophyllum. The study underscores cactus as an excellent phytoremediator.