Evaluation of the nodulated status of Vigna unguiculata probed by the JIP-test based on the chlorophyll a fluorescence rise

Abstract

Chlorophyll a fluorescence is a useful and non-invasive tool to screen for the effects of many biotic and abiotic parameters on photosynthesis in plants. The fluorescence of leaves after light excitation was measured with a portable fluorimeter (Plant Efficiency Analyser, built by Hansatech Instruments King¿s Lynn Norfolk, PE 30 4 NE, GB) and the subsequent data were analysed using the JIP-test which produces parameters indicating PSII and photosynthesis activity. Seeds of Vigna unguiculata were sterilised before germinating and planting in Magenta jars (used in hydroponics culture) with a nutrient solution without nitrate (B&D solution). Half of the plants were inoculated with Rhizobium sp. NGR234 (1019 bacteria/ 100 µl) at roots level. Each half was then further divided and treated with KNO3 to produce four treatments. During 6 weeks measurements of several hundred measurements of 2 seconds are made on the leaves of inoculated and control plants, with or without different nitrate (KNO3) concentrations. Preliminary results obtained suggest that this technique can detect nodulation. The results of KNO3 and the influence of nodulation of primary photosynthesis will be discussed in respect to the modifications observed in the fast fluorescence rise O-J-I-P.