Characteristics of the Photosynthetic Apparatus and CO2-Fixation in the Flower Bud of Lilium. I. Corolla

Abstract

In order to test the positive net CO2-fixation ability of tepals in the flower bud of Lilium hyb. enchantment, photoautotrophic characters were studied during pollen development in tepals and then compared with those in the leaf. Although mesophyll structure, plastid ultrastructure, stomata density, and chlorophyll content were significantly different in both organs, tepals performed positive net CO2-fixation from the microspore mother cell stage up to pollen mitosis but not during pollen maturation. The measurements of CO2-fixation were performed in the linear part of the saturation curve of the L5 leaf at 100 μmol photon m-2 s-1. In the tepals, CO2-fixation} reached its maximal intensity at the tetrad stage with 1.83 ± 0.12 μmol CO2 m-2 s-1, against 3.17 ± 0.27 μmol CO2 m-2 s-1 in the L5 leaf. Under these conditions, tepal CO2-fixation corresponded to 57.7% of the leaf assimilation, whereas the maximum chlorophyll concentration in the tepal represented 21.9% of the chlorophyll concentration in the leaf. The flower 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 photosynthates.