Photosynthetic gas exchange characteristics in <i>Jatropha curcas</i> L.

Abstract

The use of Jatropha (Jatropha curcas L.) as a source of biofuel has been well-documented. However, the physiological characteristic and growth analysis studies of Jatropha have received considerably lesser attention. In the present study, to confirm the physiological characteristics of Jatropha, we measured the leaf gas exchange characteristics in response to various environmental conditions. Seedlings were grown in 1/5,000 a pots for 2-3 months under greenhouse conditions. Leaf gas exchange rates were measured in a handmade assimilation chamber (26x30x9 cm), in which a fully expanded whole leaf could be set. Based on the leaf gas exchange characteristics, Jatropha was considered to be a C-3 photosynthesis plant. The photosynthetic rate ranged between 10 and 25 mu mol m(-2) s(-1) and light saturation generally occurred at 500-1,000 mu mol m(-2) s(-1) photon flux densities (PFD), depending on the growth conditions and leaf positions. Leaf conductance and transpiration rates were saturated at 400-1,000 mu mol m(-2) s(-1) PFD, also depending on the growth conditions and leaf positions. Maximum rates of transpiration and leaf conductance were 2-6 mmol m(-2) s(-1) and 200-1,200 mmol m(-2) s(-1), respectively, which are very similar to those in C-3 rice plants. Optimum temperature for photosynthesis was approximately at 25-30 degrees C and the maximum rate was 20 mu mol m(-2) s(-1). Application of varying vapor pressure difference (from 1 to 3 kPa) did not affect the photosynthetic rate. Photorespiration in Jatropha was 28.5%, which is within the range of typical C-3 plants. Based on the photosynthetic parameters presented in this study, field performance of Jatropha under severe environmental condition is discussed.