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Shade effect on photosynthesis and photoinhibition in olive during drought and rewatering
- Sofo, Adriano, Dichio, Bartolomeo, Montanaro, Giuseppe, Xiloyannis, Cristos
- Agricultural water management 2009 v.96 no.8 pp. 1201-1206
- shade, photosynthesis, photoinhibition, olives, Olea europaea, plant-water relations, drought, temperature, Mediterranean climate, semiarid zones, gas exchange, chlorophyll, fluorescence, photosynthetically active radiation, solar radiation, stomatal conductance, plant stress, carbon dioxide, plant response, Italy
- Olive tree (Olea europaea L.) is commonly grown under environmental conditions characterised by water deficit, high temperatures and irradiance levels typical of Mediterranean semi-arid regions. Measurement of gas exchange, chlorophyll content, chlorophyll fluorescence and photoinhibition was carried out on two-year-old olive trees (cv. 'Coratina') subjected to a 21-day period of water deficit followed by 23 days of rewatering. At the beginning of the experiment, plants were divided in to two groups and subjected to different light regimes: exposed plants (EP) under a mean photosynthetically active radiation (PAR) at mid-day of 1800μmolm⁻² s⁻¹ and shaded plants (SP) under a mean PAR of 1200μmolm⁻² s⁻¹. The effect of drought and high irradiance levels caused a reduction of gas exchange and photosystem 2 (PSII) efficiency, in terms of quantum yield of PSII (Φ PSII) both in EP and SP. Shading conditions allowed plants to maintain a high photosynthetic activity at low values of stomatal conductance, whereas in EP the reductions in photosynthetic efficiency and intrinsic water efficiency were due to non-stomatal components of photosynthesis. The decrease in photosynthetic activity and the increase of photoinhibition under drought were more marked in EP than in SP. Full sunlight caused in EP a higher non-photochemical quenching, whereas SP showed a better photochemical efficiency. The information here obtained can be important to understand the mechanisms by which olive plants can minimize photoinhibition when subjected to simultaneous abiotic stresses.