Floral Morphogenesis And Metamorphose In Ranunculaceae And Their Systematic Significance

Flower, as the special reproductive organ of the Angiosperms, are believed to be morphologically the most complicated parts of Angiosperms. The floral diversity patterns of the angiosperms are more complex than the reproductive organs in other plant groups. The characteristics of the floral organs reflecting the systematic significance and taxonomic position of the group most exactly and correctly. The question of the floral origin and evolution become a leading question to investigate the origin of the angiosperm. At present one of the key respects to study the floral evolution of the angiosperm is to study the living basal angiosperm, such as ANITA and Ranalean.Ranunculaceae is a most natural and a world wide distributed family with 59 genera. It is considered as not only the most primitive family of the living herbaceous angiosperms, but also one of the basic groups of eudicots. Ranunculaceae is the most diversity family among the Ranunculales, which main reflects on the variety of flower patterns and structures. There have been a lot of reports on the morphology, anatomy, and molecular systematics on Ranunculaceae. With regarding to the flowers of the family, such as the floral structure, morphology and the relationships between the floral organs, have been focused mostly on the mature flowers. A mature flower is one of the developmental stages, it contains only the information of the mature stage, but can not embody all the developmental information of the flower. Therefore, many details of the floral initiation and development in the family are still unknown to us. To expand the phylogeny knowledge of the flowers of Ranunculaceae and enrich the floral pattern and structures, a dynamic viewpoint is needed to consider the process of the floral initiation and development.The metamorphosed flowers in Ranunculaceae have been found in Anemone Linn., Adonis Linn, and Oxygraphis Bge. In the metamorphosed flowers of Anemone rivularis Buch.-Ham. ex DC. var. flore-minore Maxim., all of the metamorphosed floral organs can change into leaf-like organs and showing a different metamorphosed degrees. The most metamorphosed floral organ has long stipe, three or five lobed, and with dense stomata and hairs on both surfaces. A continuous gradient in aspects of the number, the size, the color, the shape, the margin, the stomata and the hairs as well asthe venation between the normal and the metamorphosed organs could be found.In this study the floral morphogenesis and metamorphosis of the representative genera from different subfamilies, tribes, and subtribes in Ranunculaceae (s. 1.) in China were observed. The results showed that:1. All of the floral organs initiate in a spiral, 2/5 sequence, and spirally arranged at anthesis; but the plastochron between the perianth is different in Aquilegia Linn., Thalictrum Linn., Clematis Linn., and Kingdonia Balf. f. et W. W. Smith. And the arrangement is whorl at anthesis. We conclude that the spirally arranged floral organs is primitive, the whorl arranged are derived in Ranunculaceae.2. The flowers of different genera of Ranunculaceae are unsymmetrical in morphogenesis.3. The sepal primordia of Ranunculaceae are different from other floral organs. Considered with the metamorphosed sepals in flowers of Anemone rivularis var. flore-minore we deem that the sepal origins from bract in the family.4. The petals are special named as honigblatt in Ranunculaceae. In the species of Ranunculaceae the petals are with or without nectary. Petals are morphological changeable. In Paeonia Linn., petals are resemble with that of the bracts and sepals, but different with the stamens in shape and position in morphogenesis. But in other genera the shape of the petal primordia is resemble to that of the stamens. The petal is retard in their early development stages compared with stamen. Thus we think the petal is either evolved from bract (Paeonia) or from stamen (excluding Paeoni) in Ranunculaceae.5. The initiation of the stamen is centripetal (excluding Paeonia). But the development sequence and the occurrence of the microspore are diversity: there are centripetal, centrifugal and from the center to the tip and the base in a longitudinal section of the flowers.6. The carpels possess different morphology during the carpel development. It can be divided into four types according to the closing of the carpels: 1) The carpel primordia forms a longitudinal depresses at the base and the depresses runs through the carpel in later developmental stages. The carpel resembles a conduplicated leaf before the carpel closes up. The closure of the carpel is synchronizate. 2) The carpel primordia forms a rounded depresses at the base and the depresses runs through the carpel in later developmental stages. The closure of the carpel is not synchronizate. 3) The carpel primordia forms a longitudinal depresses at the base, and then the base of the carpel curved and connected at the base. 4) The carpel differentiates into a basal stalk and an upper blade. The stalk will develop into a short ovary stalk in the later developmental stages. The blade becomes slightly concave at the base and conduplicated later. The concave disappear at the top of the carpel.7. The flower pattern diversity of Ranunculaceae is not only on the mature structures but also on the initiation and development of the floral organs. During the ontogeny process the same floral organ also have different characteristics.8. From an ontogeny point of view, we considered that: 1) Paeonia should exclude from Ranunculaceae. 2) Aconitum Linn, and Delphinium Linn, have high similarity in floral morphogenesis. 3) The floral morphogenesis of Aquilegia Linn, issimilar to the genera of Trib. Delphineae. 4) The floral morphogenesis of Thalictrum Linn, of Subfam. Thalictroideae is not similar to the Aquilegia of the same subfamily but similar to that of the genera of Subfam. Ranunculoideae. 5) The floral morphogenesis of Anemone Linn, of Subtrib. Anemoninae, Trib. Anemoneae, Subfam. Ranunculoideae is similar to that of Pulsatilla Adans. in the same subtribe. 6) The genera, Callianthemum C. A. Mey. and Adonis of Subtrib. Adodininae of Trib. Ranunculeae, show the high resemblance in floral morphogenesis and they relative with Oxygraphis Bge.9. The phenomenon of Anemone rivularis var. flore-minore that the floral organ expressed characteristics of leaf-like organ was considered to be an atavism. The characteristics, such as greenish, the anastomosous venation, the stomata and hairs on both surfaces, and the trilobes that with lobelet or serrature, show the leaf-like tendency of the metamorphosis. Therefore we concluded that the ancestor of the floral organ is leaf like organ, or at least during the early evolution of the floral organ the leaf like organ once occurred. Considered the metamorphosed flowers of Adonis and Oxygraphis we conclude that the flower organs had the same origin and are homeosis with each other and evolved from leaf-like organ.