PMS Instrument Company http://www.pmsinstrument.com/
Manufacturer of pressure chamber instruments for measuring plant water potential and irrigation scheduling. Contains product information as well as tutorials on using a pressure bomb.
PP Systems http://www.ppsystems.com/
Manufacturer of portable photosynthesis/respiration measurement instrumentation, CO2 and H2O Infrared Gas Analyzers for lab and field, portable spectrometer, and environmental sensors.
ADC BioScientific http://www.adc.co.uk/
Manufacturers of instrumentation for measuring photosynthesis, transpiration, chlorophyll fluorescence, sap flow, and gas exchange.
Walz http://www.walz.com/
Producer of sophisticated photosynthesis measuring systems. The product line ranges from PAM Chlorophyll Fluorometers to measuring systems of plant gas exchange for physiological and ecophysiological research.
Apogee http://www.apogee-inst.com/
Products used to measure radiation and leaf temperature, ordering information, and research and development being undertaken.