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Resiliency of the Carob or St. John's Bread Tree to Climate Change
Reference
Osorio, M.L., Osorio, J., Vieira, A.C., Goncalves, S. and Romano, A. 2011. Influence of enhanced temperature on photosynthesis, photooxidative damage, and antioxidant strategies in Ceratonia siliqua L. seedlings subjected to water deficit and rewatering. Photosynthetica 49: 3-12.

Background
The authors write that "water deficits and high temperature are major abiotic stress factors restricting plant growth and productivity in many regions," and they thus say that "the impact of climate change on temperature and rainfall patterns is of great importance in determining the future response of tree crops to new environmental conditions," which they assess for the Carob or St. John's tree (Ceratonia siliqua) that grows in the Mediterranean area, where they state that water stress will be the most important factor limiting plant growth throughout the remainder of this century.

What was done
Impacts of drought and high-temperature stresses on photosynthesis, energy partitioning and membrane lipids, as well as the potential ability of Carob trees to attenuate oxidative damage, were investigated in young seedlings growing within controlled-environment chambers, where they were rooted in 3-dm3 pots filled with a 2:1 mixture of a fertilized substrate and natural soil, and where they were maintained under two thermal regimes -- low and high temperature (LT: 25/18°C; HT: 32/21°C) -- and three soil water conditions (control, water stress and rewetting), under which conditions numerous physiological and biochemical plant properties and processes were repeatedly monitored.

What was learned
Among a number of other pertinent observations, Osorio et al. report that the decrease in net photosynthesis (PN) caused by drought was 33% in the LT chamber and 84% in the HT chamber. However, they found that "the negative effects of soil drying on PN and stomatal conductance of HT plants were no longer detected 36 hours following rewatering." And they add that "although C. siliqua seedlings exhibit clear signs of oxidative stress under drought and high temperature, they retain a remarkable ability to quickly restore normal physiological activity upon rehydration."

What it means
In concluding the report of their research, the five Portuguese scientists say they "can state that although C. siliqua seedlings exhibit clear signs of oxidative stress under drought and high temperature, they retain a remarkable ability to quickly restore normal physiological activity upon rehydration, which let us believe that they can satisfactorily deal with predicted climate warming and increased soil drying in the Mediterranean area."

Reviewed 6 July 2011