CHARACTERISTICS OF THE PHOTOSYNTHETIC APPARATUS AND CO2-FIXATION IN THE FLOWER BUD OF LILIUM - I - COROLLA

In order to test the positive net CO2-fixation ability of tepals in th e flower bud of Lilium hyb. enchantment, photoautotrophic characters w ere studied during pollen development in tepals and then compared with those in the leaf. Although mesophyll structure, plastid ultrastructu re, stomata density and chlorophyll content were significantly differe nt in both organs, tepals performed positive net CO2-fixation from the microspore mother cell stage up to pollen mitosis but not during poll en maturation. The measurements of CO2-fixation were performed in the Linear part of the saturation curve of the L-5 leaf at 100 mu mol phot on m(-2) s(-1). In the tepals, CO2-fixation reached its maximal intens ity at the tetrad stage with 1.83 +/- 0.12 mu mol CO2 m(-2) s(-1), aga inst 3.17 +/- 0.27 mu mol CO2 m(-2) s(-1) in the L-5 leaf. Under these conditions, tepal CO2-fixation corresponded to 57.7% of the leaf assi milation, whereas the maximum chlorophyll concentration in the tepal r epresented 21.9% of the chlorophyll concentration in the leaf. The flo wer bud of Lilium may be considered not solely as a sink structure for the whole plant but also as a partly autonomous organ in terms of pho tosynthates.