Photosynthesis: Fundamentals and advances

Abstract

Photosynthesis is one of the most incomparable and meticulous metabolic processes that maximize the use of available light, carbon and nitrogen and minimizes the destructive effects of surplus light. Indeed, photosynthesis comprises of two major reactions that occur in separate parts in the chloroplast. The light reactions take place in the thylakoid membrane which generates ATP and NADPH while dark reactions (so called Calvin-Benson cycle) exploit these ATP and NADPH to reduce carbon CO2 (carbon-di-oxide) to carbohydrates (CH2O) in the stroma of chloroplast. In plants various carbon fixation mechanisms are evolved naturally such as, less efficient C3 carbon fixation having photorespiration, more efficient C4 carbon fixation having cellular CO2 pumping system for avoiding photorespiration and CAM (Crassulacean acid metabolism) carbon fixation for escaping transpiration during day. Besides plant proceeds different alternative sinks for carbon fixation under surplus light. Chlorophyll fluorescence is one of the most influential and advanced technique for studying photosystems health but on the other hand photo inhibition and ROS (reactive oxygen species) generation are unfortunate for photosystems during various stresses. However, photo inhibition and ROS generation are obligatory during stresses whereas chloroplastic antioxidants are accountable for ROS regulation in plant cells.These insight between fundamental and advance information on photosynthesis assist to switch less efficient C3 rice to highly efficient C4 rice development to feed the ever-increasing population in the globe. Therefore, this article reviews fundamental aspects of photosynthetic machineries, underlying physiological, biochemical and molecular mechanisms and highlighted the modern scientific achievements on C4 rice development.