Characteristics of the photosynthetic apparatus and CO2-fixation in the flower bud of Lilium. II. Anther

We investigated${\rm CO}_{2}\text{-fixation}$potential in the flower bud of Lilium hyb. enchantment by testing the ability of inner flower organs to perform photosynthesis during pollen development. We first showed that photosynthetically active radiation crosses the tepals and reaches the inner fertile organs. Despite the absence of leaflike photoautotrophic tissue, the anther exhibited most characteristics compatible with${\rm CO}_{2}\text{-fixation}$from premeiosis to the vacuolated microspore stage: (1) chlorophyll fluorescence and anatomical structures associated with photosynthetically active tissues were localized in the connective tissue, the epidermis, the endothecium and the middle layers; (2) in these cell types, plastids contained well-developed thylakoids and grana; (3) the photoautotrophic cell layers in the anthers had a chlorophyll concentration reaching 17.6% of the L5leaf concentration and a Chl a/b ratio within a range of 1.5-1.9; (4) stomata density was more than twofold higher in the anther than in the L5leaf; and (5) in anthers,${\rm CO}_{2}\text{-assimilation}$at$100\ \mu {\rm mol}\ \text{photon}\ {\rm m}^{-2}\ {\rm s}^{-1}$was$2.3\pm 0.29\ \mu {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$at the tetrad stage, which represented 72.6% of L5leaf${\rm CO}_{2}\text{-fixation}$. In the filament, the ovary, and the style, the Chl a/b ratio was similar to that of the anther, but plastid membranes were less developed and the low stomata density (less than 2 stomata${\rm mm}^{-2}$) did not allow these organs to perform gas exchange rapidly.