Photosynthesis, inorganic plant nutrition, solutions, and problems.

A brief account is given of the research that D.I. Arnon did before he ventured into the field of photosynthesis, viz. his work on inorganic plant nutrition in the laboratory of D.R. Hoagland. The connection between the two areas is indicated. In his work on plant nutrition Dr Arnon emphasized the role of specific nutrients and, with P.R. Stout, formulated a definition of essentiality that is used to this day. It is now necessary, however, to take into account elements not meeting their criteria of essentiality, as shown by a consideration of the element silicon.