Chlorophyll a fluorescence as a technique to evaluate the quality of Rhododendron simsii

For evergreen azalea (Rhododendron simsii Planch.), the ability to flower and the duration of the flowering period are the determining parameters for quality. This quality is related with cultural conditions determined by the growers. A plant with a good internal quality, i.e, a good performing photosynthesis system, is able to produce sufficient energy for uniform and long lasting flowering. Chlorophyll a fluorescence (CF) measurements can be used to quantify the properties of the photosynthetic apparatus. The best moment to measure the internal quality is just before the forcing period. At this time, plants have to prove their capacities to produce flowers. An experiment was set up to determine the CF parameter and optimal measuring condition that resulted in the largest relative difference between plants with different quality levels. Measuring the quantum efficiency of photosystem II (Phi (II)) at 400 mu mol m(-2) s(-1) resulted in the largest relative difference. A second experiment was set up to detect differences between plants from different growers. Significant linear relations were found between Phi (II) and flowering uniformity for the three tested cultivars. A significant linear relation between Phi (II) and duration of the flowering period was found only for `Mw. G. Kint'.