Radiation use efficiency and instantaneous photosynthesis at different growth stages of wheat (Triticum aestivum L.) in semi arid ecosystem of Central Punjab, India

Abstract

The instantaneous canopy net photosynthetic rate (Ac) and photosynthetic radiation use efficiency (PhRUE) were investigated diurnally at different growth stages of wheat during two seasons 2009-2010 and 2010-11. Diurnal changes in Ac were synchronized with changes in incident photosynthetic photon flux density (PPFDo) throughout the experimental period during both the seasons. Regardless of growth stages, high Ac values were always observed around noon, when there was a high photosynthetic photon flux density (PPFD). In addition, the highest AC values were noticed at heading stage, when compared to other growth and development stages of wheat. With respect to PhRUE, the highest values occurred in the active tillering stage and decreased gradually upto soft dough stage during both the seasons. PhRUE was lowest after heading stage for wheat crop in both seasons, corresponding to decrease in photosynthetically active leaf area, another explanation for the decrease in RUE is a decrease in crop growth rate. Regarding diurnal changes in PhRUE, study revealed that it was always higher during early morning and evening time of the day at all the stages of the crop. The seasonal PhRUE of wheat was observed to be 1.21 g MJ-1 and 1.27 g MJ-1, respectively during two seasons.