Reproductive Biology Of The Distylous Species Of P. Orientale

In this study, we analysized the plant morpho-anatomy, breeding system and pollination biology of P. orientale, to reveal their reproductive biology characteristics, the evolutionary trends and mechanism of their distyly.The anatomical structure characteristics of leaf stem and root were observed using paraffin method, and effect to its survival was also discussed based on its structure characteristics. The results are as follows:The roots of the two flower type species, are made of epidermis, cortex and vascular cylinder. Primary xylem root contains a lot of crystals, besides secondary xylem developed. The leaves are typically dorsi-ventral. The vascular tissue which has a small proportion in stem of two species contains developed phloem fibers. Stem cortical and medullary are proportion of more than 70%. So its poor resistance to low temperature and aboveground part cannot survive in the winter. The stigma papilla width of two types are not significant(P>0.05), but the stigma papilla length and stigma width are significant(P<0.001). Ovary are oval, there a channel for pollen germination to the embryo sac when fertilized.Distyly was clearly confirmed in P. orientale. Long-styled and short-styled morph exhibited a precise reciprocal herkogamy, which were significantly correlated with corolla length. Research showed that anther heights, the tepals,stigma, pollen size, number were dimorphic(P<0.01). Compared with the pins, the thrums had larger tepals, and the stigma had more but shorter papillae, the anther produced significantly bigger pollen grains but less numbers. There was no significant difference between long-styled and short-styled in tepal length(P>0.05).The micromorphological characteristics of pollen grains were spherical or suborbicular, with irregular margins and scattered holes. Thrips, ants and flower flies were the main visitors to the flowers.The anthesis of short-styled and long-styled flower of P. orientale lasted15-16 d and 13-14 d respectively. Pollen germination rate is higher, the length of columnar pollen germination rate was no significant difference of two types(P>0.05). In field survey, there are single types, usually most types ratio to 1: 1, but a few deviation of 1: 1, and when the population is relatively small(<10 m2), they tend to appear single types, suggesting P. orientale flower ratio may be related to the size of the populations.Artificial pollination revealed that pollen tubes shape were normal in both morphs where pollen tubes reached the ovary 0.5 h after pollination. Not all pollen tubes growing down the stylar canal and ovary wall could able to reach the ovary.Indicating that it was chalazogamy in P. orientale.Long-styled and short-styled morph intramorph fruit sets were 14.00% and 13.33%, self- pollination fruit sets were 4.62% and 2.86%, intermorph fruit sets were 43.33% and 44.61%, Indicating that self- pollination showed some affinity, but the fruit sets were low, the flowers were still dominated intermorph.