In this reporting period, plant uptake and phytotoxicity studies were performed on several (previously reported) multi-metal materials. Plant uptake study was performed using Citrus reshni (Cleopatra mandarin) seedling in the greenhouse. Eleven-month old seedlings were foliar sprayed with a hand-pump sprayer with the following treatments: 300 ml of MM25C75M (800 µg/ml Cu2+, 2400 µg/ml Mg2+), MM25C75Z (800 µg/ml Cu2+, 2400 µg/ml Zn2+), MM10C45M45Z (300 µg/ml Cu2+, 1350 µg/ml Mg2+, 1350 µg/ml Zn2+) and deionized water as untreated control (UTC). The pots were covered with Parafilm to prevent treatment solutions to contact with soil and seedling roots. After 72 h incubation, plants were carefully removed from the soil and gently washed with 1% detergent and 0.1% HCl. Leaves, roots, and stem sections were separated after washing and left in an oven (Cabela’s Inc, Sydney, NE) at 50 ºC for 72 h. The dried leaves, stems and roots were pulverized with mortars and pestles. One gram of dry powder of leaves, stems, and roots was acid digested (EPA method 3050 B “Acid Digestion of Sediments, Sludge, and Soil). After digestion, the digestate was filtered with Whatman No. 42 filter paper and the final volume was 20 ml. Cu, Zn and Mg content in leaves, stems, and roots were quantified with Atomic Absorption Spectroscopy (AAS). MM25C75M (142.8 ± 28.4 µg/ml Mg2+) showed significant higher Mg2+ uptake roots compare to untreated control (71.6 ± 0.73 µg/ml Mg2+). MM25C75M (Leaves: 0.54 ± 0.16 µg/ml Cu2+, Roots:1.82 ± 0.09 µg/ml Cu2+, Stems: 0.29 ± 0.08 µg/ml Cu2+) showed significant Cu2+ uptake by leaves, roots and stems compare to untreated control (Leaves: 0.16 ± 0.01 µg/ml Cu2+, Roots: 0.84 ± 0.06 µg/ml Cu2+, Stems: 0.09 ± 0.01 µg/ml Cu2+). MM25C75Z (1.85 ± 0.04 µg/ml Cu2+) showed significant Cu2+ uptake by roots compare to untreated control (0.84 ± 0.06 µg/ml Cu2+). MM25C75Z (5.6 ± 0.13 µg/ml Zn2+) and MM10C45M45Z (7.7 ± 0.03 µg/ml Zn2+) showed significant Zn2+ uptake by roots compare to untreated control (2.2 ± 0.004 µg/ml Zn2+). According to our results, MM25C75M showed significant leaf uptake of Mg2+ and Cu2+ and movement to roots. MM25C75Z showed significant leaf uptake of Zn2+ and Cu2+ and movement to roots. Similarly, MM10C45M45Z showed significant leaf uptake of Zn2+ and movement to roots. Phytotoxicity of MM25C75M, MM25C75M, and MM10C45M45Z and selected controls was evaluated on Citrus reshni (Cleopatra mandarin) eleven-month seeding in the greenhouse. All the materials were foliar sprayed by using a hand-operated pump mist sprayer at 800 µg/ml of Cu2+. Mg(NO3)2 (2400 µg/ml Mg2+), Zn(NO3)2 (2400 µg/ml Zn2+), and Cu(NO3)2 (800 µg/ml Cu2+) were selected as controls. Visual observations were conducted at 24, 48, and 72 h post-spray applications. After 3 days of incubation, Zn(NO3)2 and Cu(NO3)2 treated plants showed severe leaf browning deformation. MM25C75M (800 µg/ml Cu2+, 2400 µg/ml Mg2+), MM25C75Z (800 µg/ml Cu2+, 2400 µg/ml Zn2+), and MM10C45M45Z (600 µg/ml Cu2+, 2700 µg/ml Mg2+, 2700 µg/ml Zn2+) exhibited no damage to the plant. This year citrus canker field trial includes both MM25C75M and MM25C75Z.
We have designed and synthesized Fe oxide based material for facilitating systemic movement of EPA approved Cu bactericide/fungicide such as Cu salt of fatty acid. Research results on this material will be shared in future reports.