Abstract: In natural condition, the capacity of plants to generate negative air ions (NAIs) is very weak. However, a pulsed electrical field can result in a substantial improvement of the capacity in NAI generation. To investigate the mechanism underlying NAI generation by plant following the pulsed electrical field stimulation, the present study examined the generation of NAI in Clivia miniata, Echinocactus grusonii, and Chlorophytum comosum among the ten tested plant species (Guzmania lingulata etc) in the  presence of a pulsed electrical field, which possess strong capacity of generating NAI under natural conditions. The results showed that various parameters of pulsed electrical field affected the generation of NAI in the plants. Each plant had its own optimal pulsed electrical field with combination of parameters for the efficient generation of NAI: C. miniata with A₄B₄C₄ (A₄,U = 2.0×10⁴ V; B₄, T=2.0 s; C₄, τ=90 ms), E. grusonii with A₄B₁C₃ (A₄, U=2.0×10⁴ V; B₁, T=0.5 s; C₃, τ = 65 ms) and C. comosum with A₃B₁C₂ (A₃,U=1.5×10⁴ V; B₁, T=0.5 s; C₂, τ=35 ms). With the application of a pulsed electrical field to a plant, the higher voltage in the plant, the greater capacity of NAI generation was (P<0.05). With the enhancement of light intensity, the ability of the plant to generate NAI significantly increased (P<0.05). A plant’s capacity of NAI generation was closely related to the characteristics of leaf stomata. Greater degree of stomatal opening and stomatal density facilitated a stronger ability of the plant to generate NAI (P<0.05). In sum, these results suggested that NAI generation by plants was a complex physiological process that was influenced by several factors, including the presence of pulsed electrical field stimulation, light intensity, and plant characteristics.

Key words: soil heavy metal, semi-variance, paddy field, spatial variation, correlation analysis., soil nutrient, kriging interpolation