Use of combined fluorescence and gas-exchange measurements to assess processes limiting photosynthesis under stress.

A system for the rapid simultaneous measurement of both chlorophyll fluorescence quenching (using a modulated light system), and of CO 2 and water vapour exchange by leaves was used to study the effects of water deficits on photosynthesis in apple in a laboratory study and in sorghum in a field study. Equipment compared in the field included Hansatech modulated fluorescence system, Walz modulated fluorimeter and Plant Stress Meter (Biomonitor) for chlorophyll fluorescence and Analytical Development Corporation