Evaluating physiological traits of Coffea canephora clones intercropped with Hevea brasiliensis

In this study, we evaluated the physiological response of the photosynthetic apparatus [using chlorophyll a fluorescence (ChlaF) measurements], changes in leaf nutrient contents, and productivity of 16 Coffea canephora clones grown alone (NC, full sunlight) or intercropped with Hevea brasiliensis (IC, shaded). Shade from H. brasiliensis trees influenced the physiological performance of coffee plants. Some of these coffee clones achieved clear responses to shading by rubber trees, indicating that the responses of coffee plants to intercropping are genotype-specific. The PSII complex of the NC plants was more susceptible to photoinhibition, especially clones 02, 73, 143, and 109A, which had increased minimal fluorescence, specific energy fluxes per reaction centers, maximum photochemical quantum yield, quantum efficiency of electron transfer from Q_A ^- to the electron transport chain beyond Q_A ^-, and number of active PSII reaction centers per cross section, performance index for conservation of energy from captured excitons to reduction of intersystem electron acceptors, and lower maximum fluorescence. In contrast, the higher photosynthetic efficiency and productivity of the clones under shaded conditions indicated their potential for cultivation together with H. brasiliensis.