Photochemical activity of single chloroplasts recorded by the use of nuclear track emulsion

Stories and photographs of William A. Arnold (1904-2001), a pioneer of photosynthesis and a wonderful friend

William A. Arnold discovered many phenomena in photosynthesis. In 1932, together with Robert Emerson, he provided the first experimental data that led to the concept of a large antenna and a few reaction centers (photosynthetic unit); in 1935, he obtained the minimum quantum requirement of 8-10 for the evolution of one O2 molecule; in 1951, together with Bernard L. Strehler, he discovered delayed fluorescence (also known as delayed light emission) in photosynthetic systems; and in 1956, together with Helen Sherwood, he discovered thermoluminescence in plants. He is also known for providing a solid-state picture of photosynthesis. Much has been written about him and his research, including many articles in a special issue of Photosynthesis Research (Govindjee et al. (eds.) 1996); and a biography of Arnold, by Govindjee and Srivastava (William Archibald Arnold (1904-2001), 2014), in the Biographical Memoirs of the US National Academy of Sciences, (Washington, DC). Our article here offers a glimpse into the everyday life, through stories and photographs, of this remarkable scientist.

Experiments

In this article, I have provided a brief history of my life. After tracing my family background and my early interest in physical sciences, I discuss how I entered biology under the influence of Robert Emerson. I have always enjoyed doing experiments and this led to new measurements and analyses of 'chlorophyll unit', efficiency of photosynthesis, excitation energy transfer, delayed light emission, thermoluminescence and electroluminescence in photosynthetic organisms. It is my view that discoveries are made because we follow our scientific curiosities.