Seasonal variations of photosynthesis, gas exchange, quantum efficiency of photosystem II and biochemical responses off Jatropha curcas L. grown in semi-humid and semi-arid areas subject to water stress

This study aimed to compare the physiological adaptations of Jatropha curcas in two regions with different climates, the Agreste (a semi-arid tropical climate) and the Florest zone (a semi-humid tropical climate) subject to water stress. Measurements of gas exchange and photochemical and biochemical efficiency were performed in two seasons, the dry season (September to February) and the rainy season (April and August), between 2006 and 2007. During the dry season in the Florest zone, the J. curcas plants presented better photosynthetic performance, with smaller decreases in the rates of photosynthesis, stomatal conductance and transpiration because the conditions of water availability in the soil were slightly higher than in the semi-arid region. A greater vapor pressure deficit was observed during the dry season of the semi-arid region, showing a negative correlation with the stomatal opening of the leaves, which contributed to a reduction in the values of the net photosynthetic rate. During the dry season in the semi-arid region, dynamic photoinhibition occurred in the leaves of J. curcas around mid-day, with a rapid recovery during the afternoon. However, chronic photoinhibition may have occurred in some plants with a severe water deficit. A reduction in the effective quantum efficiency was also observed during the driest months. The increase of catalase activity and the accumulation of proline, total soluble sugars and amino acids during periods of low water availability in the soil suggest that J. curcas presents an efficient protection mechanism that allows the plant to survive under drought conditions. (C) 2012 Elsevier B.V. All rights reserved.