Glossary

• Action potential — A brief, self-propagating electrical pulse across a cell membrane; found in nerves and in some plant tissues.
• Air ion — A molecule in the air carrying an electric charge.
• Ampere (amp) — The unit of electric current. A milliampere is a thousandth; a microampere, a millionth; a picoampere, a millionth of a millionth.
• Control — The untreated group in an experiment, kept alike in every other respect.
• Corona or point discharge — A faint leakage of current into the air from a sharp conductor in a strong field.
• Earth battery — Two different metals buried in moist soil and joined by a wire, producing a weak current.
• Electric field — The condition of space around a charge that exerts force on other charges; measured in volts per meter.
• Electro-vegetometer — Bertholon’s 1783 mast for bringing atmospheric electricity to plants.
• Fair-weather field — The steady vertical electric field of the atmosphere away from storms, roughly 100 to 150 volts per meter at the ground.
• Galvanic — Relating to current produced by chemical action between unlike metals.
• Haber–Bosch process — The industrial synthesis of ammonia from atmospheric nitrogen; the basis of nitrogen fertilizer.
• Influence machine — A static-electricity generator such as the Wimshurst or Holtz machine.
• Randomization — Assigning treatments by chance so that hidden differences cannot favor one group.
• Replication — Repeating each treatment on several independent plots or plants.
• Sham — A dummy treatment given to the control group.
• Triboelectric nanogenerator — A device that produces high voltage from friction between materials set moving by wind, rain or other motion.
• Volt — The unit of electrical potential, or pressure. Voltage alone does not measure energy.