Floral Development of Potamogeton richardsonii

Abstract

The inception and development of the sterile floral appendages of Potamogeton richardsonii have been re-investigated with a refined dissection technique (Sattler, 1968) and improved microtechnical methods (Feder and O'Brien, 1968). The results obtained by Sattler (1965) are confirmed, i.e., the sterile appendages are initiated at the flanks of the floral apex before the stamen primordia are formed. Consequently, they may be homologized with tepals or perianth members, although in the mature flower they are inserted at the stamen connective, due to growth between and at the base of each developing tepal and stamen. Each carpel arises as a radial primordium which becomes peltate immediately after its inception. One ovule primordium is initiated at the cross-zone. The stigma becomes bilobed. A slight outgrowth develops at the abaxial side of the style. The floral apex has a two-layered tunica. The primordia of the tepals, carpels, and ovules arise by periclinal divisions in the second tunica layer, whereas the stamen primordia are initiated by periclinal divisions in the corpus and second tunica layer. Variation in floral pattern, especially with regard to the number of appendages, has been observed in flowers near the tip of the inflorescence axis.