The Structure, Development And Systematics Of Phytolacca (Phytolaccaceae)

The genus Phytolacca is one most widely distribution genus in the family Phytolaccaceae, also is the important representation for studying the classification and systematic of Phytolaccaceae and even the Caryophyllales. Its flower was studied on structure, ontogeny and development by some authors. And its pollen, epidermis of leaf was studied to a certain extent. But there still are some problems on the structure, ontogeny and development of the pistil, which are not solved. For example, are there bounds between the carpel and axis (receptacle)? How do the papilla tissue ontogeny and develop, which united the carpels together? And where is the position of its ovule? The classification of Phytolacca has not been studied systematically in nearly one hundred years. In this paper, the plants of Phytolacca distributed in China were studied systematically as representation of Phytolaccaceae, and some important results were listed below:1. The edges of carpel are closed by papilla tissue. The papilla tissue is from the cells of epidermis of apex and the edges of carpel. The papilla tissue, the papilla on the style, which acts as stigma and the funicular obturator are united as a whole. Whatever the apocarpous or the syncarpous pistil always has papilla tissue in its center, which united all carpels. There is no distinguishing bound between the carpel and axis, but they can be distinguished from each other by the differential degree of the tissue between them.2. The vascular bundle of ovule of Phytolacca is evidently from the vascular tissue of receptacle. This point is different from general angiosperms, which ovulevascular bundle is from marginal vascular bundles. Every carpel has 3-5 vascular bundles, and any one is not bigger than others. All these vascular bundles are derived from the carpel vascular bundle at the base of carpel. This point is different from general angiosperms, which only has dorsal and marginal vascular bundles.3. The tepal of Phytolacca initiates in 2/5 spirals, the starting direction is either clockwise or counterclockwise. The stamen initiated in non-direction, and when the androecium has more stamens, the inner initiated first, then the outer. In our results, there is no corresponding relationship between the tepal and stamen organogenesis. This does not agree with Ronse Decraene. The carpels alternate with the inner stamens, and their number also equal. The ovule initiate on the ring meristem, which located in the inside of carpel. The carpel is symplicate. When the carpels are initiating, they connect together each other, and in the growing progress, the connected parts of carpels grow in different degree, so if the connected parts grew as fast as carpels, the pistil is syncarpous, otherwise apocarpous.4. The results of investigation on the leaf epidermis of the species distributed in China show that micro-morphic of leaf has some differences between the species in wax layer and the cell wall, which can be used to classification of Phytolacca.5. The results of ITS gene sequence analyzing show that the species with apocarpous pistil in genus Phytolacca is originating from two different ancients. The plants with apocarpous pistil distributed in East Asia are more evolutionary than the plants with syncarpous pistil.6. The results of cladistic analysis show that the progress of the morphological characters evolved is very complex, and that the characters are used to classify and evolutionary analysis evolved and relapsed many times, so that only used the morphological characters to study the evolution of Phytolacca is very difficult.7. The analysis of the geographical distribution of Phytolacca shows that the distribution type is the tropical Asia, Africa and America discontinuous distribution. This said that the genus originated in ancient southern continent, so itoriginated in the Early Cretaceous at lest. The analysis of the geographical distribution of the subgenus shows that they differentiated before the Neogene. 8. According to the analysis of th...