Plants can uptake, bioaccumulate and immobilize different metals in their tissues. Phytoremediation technique has been used to remove hazardous substances including heavy metals from the environment. Assisted phytoremediation is usually the process of applying a chemical additive to heavy metal contaminated soils to enhance the metal uptake by plants. The main objective of present study was to investigate the effectiveness of plant growth regulators (PGRs) and a humic substance (HS) on Ni

more »

... emediation by maize in a Ni-pollutrd calcareous soil. Materials and Methods: The experiment designed as a 5×3 factorial trial arranged in a completely randomized design with three replicates. Three kilograms of soil was placed in plastic pots and pots were watered with distilled water to field capacity and maintained at this moisture level throughout the experiment by watering the pots to a constant weight. The soils were polluted with 250 mg Ni Kg-1 as Ni-nitrate Ni (NO3)2. Six maize (Zea mays L.) seeds were planted 2 cm deep in soil and thinned to three uniform stands 1 week after emergence. Treatments consisted of three levels of soil application of commercially humic substance, HS, (0, 3, and 6 mg kg as Humax 95-WSG containing about 80% humic acid, and about 15% fulvic acid) and five levels of PGRs (0 or 10 µM GA3, IAA, BAP and SA). The HS was applied as split doses in three times at 15 day intervals along with irrigation water. The seedlings were exposed to aqueous solutions of HS 16 days after sowing for the first time. Prepared solutions of PGRs were sprayed three times at 15 day intervals from emergence. Seven weeks after planting, shoots were harvested and roots were separated from soil carefully, both parts were rinsed with distilled water and dried at 65°C for 72 h, weighed, ground, and dry meshed at 550°C. Root and shoot dry matter and Ni concentration and uptake and phytoremediation criteria were considered as plant responses. Data were statistically analyzed using SAS and SPSS software package [...]