The photosynthetic performance of plants id a good indicator of its physiological condition. If a leaf receives more sunlight than it can use in its photochemistry, excess light is dissipated by heat emission and re-emission of a small amount of chlorophyll fluorescence. Chlorophyll emits red fluorescence in the wavelengths 680-760nm which can be detected and measured using optoelectronic equipment that separates the fluoresecnce from the ambient light. When plants are under stress, either through insect pests and disease, climatic conditions including the availability of water and oxygen at the root zone, for example, photosynthetic activity will be compromised. The advantages of chloropyll fluorescence is that the measurements are quick and non invasive or destructive of plant tissue. Measurements can also be used to evaluate the relative tolerance of plants to various parameters that contribute to stressful situations and as an early warning system. For more detailed information "Fruit & Veg Tech" www.HortiWorld.com and the authors at Wageningen University.

ADC BioScientific, Cambridge, England, supplies a range of advanced Chlorophyll Fluorescence Instrumentation for field and laboratory use. The OS30P Portable Pulse Excitation Fluorometer is a small, battery operated device ideal for detailed field analysis and educational applications. The Model OS1FL is claimed to be the most portable pulse modulated fluorometer available weighing less than 2kg. An advanced portable version, the OS5FL, is indicated for more detailed analysis of chlorophyll fluorescence. The new GFP-1 Green Fluorescent Protein Meter (GFP) has been designed to accurately measure green fluorescent protein in intact leaves. The handheld, portable design enables accurate determination of GFP concentration in the field, even under ambient light conditions. The compact, probe based design allows the user to measure on intact leaves as well as samples in a petri dish. Due to its small measuring area, the instrument can be used on a wide variety of plant species, including small leafed varieties such as Arabidopsis, grasses etc. The new CCM-200 Handheld Chlorophyll Content Meter accurately determines chlorophyll content in plants and crops. Especially useful for improving Nitrogen management programs, the instrument is an ideal instrument for both research and teaching. It provides agronomists, researchers and teachers with reliable, repeatable and easy to perform chlorophyll content determinations and is claimed to be the most field efficient and affordable chlorophyll content meter on the market. For further information contact ADC BioScientific Ltd: fax 0044 1992 444567, E-mail: sales@adc.co.uk www.adc.co.uk