Photosynthetic performance of Jatropha curcas fruits

Jatropha curcas (L.) trees under north Indian conditions (Lucknow) produce fruits in two major flushes, once during autumn–winter (October–December). The leaves at this time are at the senescence stages and already shedding. The second flush of fruit setting occurs during the summer (April–June) after the leaves have formed during spring (March–April). Photosynthetic performance of detached jatropha fruits was studied at three developmental stages, immature, mature and ripe fruits. Studies were made in both winter and summer fruits in response to light, temperature and vapour pressure deficit (VPD) under controlled conditions to assess the influence of these environmental factors on the photosynthetic performance of jatropha fruits. Immature fruits showed high light saturating point of around 2000 μmol m−2 s−1. High VPD did not show an adverse effect on the fruit A. Stomatal conductance (gs) showed an inverse behaviour to increasing VPD, however, transpiration (E) was not restricted by the increasing VPD in both seasons. During winter in absence of leaves on the jatropha tree the fruits along with the bark contributes maximum towards photoassimilation. Dark respiration rates (Rd) monitored in fruit coat and seeds independently, showed maximum Rd in seeds of mature fruit and these were about five times more than its fruit coat, reflecting the higher energy requirement of the developing fruit during maximum oil synthesis stage. Photosynthesis and fluorescence parameters studied indicate that young jatropha fruits are photosynthetically as efficient as its leaves and play a paramount role in scavenging the high concentration of CO2 generated by the fruit during respiration.

► Photosynthesis and fluorescence studies were made in Jatropha curcas fruits.
► Photosynthetically fruits and bark were 20–40% as efficient as the leaves.
► Fruit showed capacity to utilize extremely low to high light for photosynthesis.
► Temperature and VPD did not have pronounced effect of Jatropha fruit photosynthesis.
► Seeds of mature fruits showed five times more respiration than its fruit coat.