Characteristics of slow chlorophyll fluorescence emission in four Coffea arabica genotypes submitted to water stress

The characteristics of slow chlorophyll (Chi) fluorescence emission were studied in fully developed leaves of coffee (Coffea arabica) cultivars Red Catuai, Catimor, H-421 (a Timer Hybrid with Yellow Catuai), and H-430 (a Timer Hybrid with Red Catuai). Fluorescence measurements were made with a Hansatech system, using leaf discs (1000 mm(2)), under continuous red irradiation (660 mn peak, photon flux density ca. 300 mu mol m(-2) s(-1)) at 35 degrees C. During dehydration, there was nea apparent Chi loss from the leaves of all genotypes, but the electron now between the two photosystems decreased. The hybrid H-421 was the least affected. On the other hand, the light reactions of photosystem 2 and its capacity to reduce the primary photosynthetic electron acceptor were mot affected by water stress.