The Warburg-effects: basic metabolic processes with reference to cancer development and global photosynthesis.

One century ago (1920), Otto Warburg (1883-1970) discovered that in liquid cultures of unicellular green algae (Chlorella sp.) molecular oxygen (O2) exerts an inhibitory effect on photosynthesis. Decades later, O2 dependent suppression of photosynthetic carbon dioxide (CO2) assimilation (the "green" Warbur geffect) was confirmed on the leaves of seed plants. Here, we summarize the history of this discovery and elucidate the consequences of the photorespiratory pathway in land plants with reference to unpublished CO2 exchange data measured on the leaves of sunflower (Helianthus annuus) plants. In addition, we discuss the inefficiency of the key enzyme Rubisco and analyze data concerning the productivity of C3 vs. C4 crop species (sunflower vs. maize, Zea mays). Warburg's discovery inaugurated a research agenda in the biochemistry of photosynthetic CO2 assimilation that continues to the present. In addition, we briefly discuss Warburg's model of metabolic processes in cancer, net primary production (global photosynthesis) with respect to climate change, trees and other land plants as CO2 removers, and potential climate mitigators in the Anthropocene.

Ernst Haeckel, ancient forests, and the Anthropocene.

In this Addendum to an article in  Nature commemorating the 100th anniversary of Ernst Haeckel's death (9 August 1919), we recall the largely forgotten fact that Haeckel (1868) was an early proponent of the concept of an "Anthropozoic Age", a 19th-century anticipation of the "Anthropocene". Haeckel in particular highlighted man's extensive remodeling of the planet in ancient forests. Earlier influences on Haeckel included Alexander von Humboldt (1769-1859) and dozens of similar writers in the 19th century Romantic era, including the Italian geologist and priest Antonio Stoppani (1824-1891), and the American diplomat and environmentalist George P. Marsh (1801-1882). Starting in the 1840s, Marsh described in extraordinary detail the destructive influence of mankind on natural ecosystems, again with particular emphasis on the destruction of forests. Marsh, like Haeckel after him, was a pioneer in describing the far-reaching human re-modeling of the planet that they and their colleagues presciently labeled the "Anthropozoic Age".