The influence of different light intensities on the growth of the tobacco aurea mutant Su/su.

Chlorophyll mutants in higher plants are often injured by high light intensities [see 14, 24]. By contrast a dominant aurea mutant in tobacco, Su/su, which was discovered by BURK and MENSER in 1964 [2], requires high light intensities for normal growth. The mutation has apparently produced a sun plant in which the inherited loss of light-absorbing pigments has been made up by an increased capacity for using light. Numerically, this characteristic is expressed by a maximal rate of photosynthesis of 230 μl O2 evolved/mg chlorophyll per min, whereas the green control var. John Williams Broadleaf only gives 45 μl O2 evolved/mg chlorophyll per min. Similar, but not as large, metabolic ratios seem to prevail between other normal green plants and their yellow-green derivatives, like Nicotiana tabacum Rg, Fla. 15, No. 63 and Dixie Shade.