The Golden Apples of the Sun: the History of Photosynthesis—so Far

Abstract

This article reviews the start of life and of photosynthesis on the Earth. A pivotal evolutionary event in photosynthesis was the ability to use water as the source of hydrogen in the photosynthetic reaction, which occurred about 2.35 billion years ago. This opened up the possibility for photosynthetic organisms to live anywhere on the surface of the Earth where light and water occurred—and secondarily allowed the build-up of oxygen in the biosphere and atmosphere. The accumulation of molecular oxygen allowed the evolution of aerobic respiratory systems with much greater efficiency in output of organically-derived energy. In turn this allowed the evolution of large complex eukaryotic cells by endosymbiosis. The chloroplast was the result of one endosymbiotic development, now found in many phyla of photosynthetic protists (algae) and in land plants. The multicellular land plants, which evolved from streptophyte green algae, now account for a major part of the total bioenergy production from photosynthesis on the Earth. However, the basic mechanism of photosynthesis has changed very little in the last 2 billion years. In the future, radical changes will be necessary to make bioenergy production from algae and plants more efficient and more competitive with other methods of solar energy conversion.