Copyright 2007 Accademia dei Georgofili
Olive (Olea europaea L.) is one of the most cultivated trees in Mediterranean agro-ecosystem. The wide diffusion of this species is due to its high adaptability to the climatic conditions of the Mediterranean areas characterised by wet and mild winter, with lower temperatures rarely below 0°C, and dry and hot summer. Evolution processes in these climatic conditions have enable the species to develop moderate tolerance to drought, salinity and high temperatures stresses, while plants have low tolerance towards low temperatures and anoxic conditions. Moreover, in the last decades human activities have increased, by air, water and soil pollution, the types of the environmental constrains olive plants have to cope with. Under extreme climatic or suboptimal soil conditions olive plants undergo to stress processes, which can determine negative effects on plant metabolism and productivity. In this review article the physiological aspects of olive reaction to environmental stresses are presented and discussed. Several research activities have tried to understand the physiological basis of olive reactions to drought, salinity and low temperatures because these stresses are the most relevant in the Mediterranean agro-ecosystem. These studies proved the high adaptability of olive trees to drought and salinity levels, which results critical for many fruit trees. In addition, each stress factor determine specific physiological effects and a wide variability in genotypes performance was highlighted. Studies on olive reactions to environmental pollution proved that these stresses very often induce subliminal effects, which could impair productivity in long term. Future researches should deserve more attention at the molecular and biochemical mechanisms involved in stress perception, transduction, and tolerance. More interest should be also committed to the interactions between different types of stresses and to the dissection of the common response mechanisms at the molecular level between drought, salinity and temperature. This approach will enable olive improvement toward unfavourable environmental conditions, especially under the future global change scenarios predicted for the Mediterranean agro-ecosystem in the next decades.
