Chloroplast fluorescence of C4 plants : I. Detection with infrared color film.

The precise spectral responses of infrared color film permit a rapid qualitative detection of the in situ fluorescence properties of chloroplasts in C4 plants. Fluorescing mesophyll and granal bundle-sheath chloroplasts appear yellow, indicating a predominance of far-red over infrared fluorescence. In contrast, fluorescing agranal bundle-sheath chloroplasts appear red, indicating a predominance of infrared over far-red fluorescence. There is a strong positive correlation between lamellar appression and the ratio of far-red to infrared fluorescence as recorded by infrared color film. The red versus yellow color of bundle-sheath chloroplast infrared photographs is used to separate the 18 species of C4 plants and 2 species of C3 plants examined into two basic groups. This separation is compatible with a separation based on lamellar ultrastructure of bundle-sheath chloroplasts.