Studies On The Reproductive Biology Of Luculia Pinciana

Luculia pinciana Hook.evergreen shrub or tree, attached to Luculia in Rubiaceae family. It is located in southeast Asia, and Yunnan province is one of the main distribution area. L. pinciana bears great ornamental value and development potential attributing to its long flowering phase, glaring color and fragrance of flowers, elegant plant shape. In order to lay down a correct strategy for selection and breeding purpose and provide theoretical basis for systematic evolution, reproductive system, development of microsporogenesis and megasporogenesis, properties of flowering and bearing, compatibility of interspecific cross and seed germination characteristics were studied. The main progresses were summarized as follows:(1) Reproductive system.The number of inflorescence per pin plant was significantly higher, while the corolla tube and the stigma lobe of the pin flower were significantly shorter in length.The pollen viability of L. pinciana reached its peak value around 70% 8 hours after the anther loosed pollen, and its stigma had peroxidase activity from the early phase of the anther loosing pollen until the end of flowering. The pollen-ovule ratio of pin flower and thrum flower was 1641.7±365.84 and 947.3±194.84 respectively and both of their out-crossing index was 3. Combining with the result of emasculation, bagging experiment and pollinating observation, we concluded that L.pinciana should be anthophilous flower plant in the field.The compatible pollen of pin flower and thrum flower was respectively provided by the same type flower of different plant and the pin flower. The distyly of L. pinciana born not only morphological but also functional sense.(2)Megasporogenesis, microsporogenesis and development of female and male gametophyte. There was four chambers in the anther of L. pinciana,and its anther wall from outside to inside followed by epidermis, endothecium, middle layer and tapetum. Dicotyledonous type and glandular tapetum were applied to the development of anther wall. Middle layer and tapetum dissolved gradually in the course of pollen development, and mature anther wall only retain the epidermis and drug interior wall.Meiotic division in microspore mother cells were followed by simultaneous cytokinesis and resulted in tetrahedral tetrads. Pollen grains were two-celled at mature stage. Ovary owned two-bedroom, with each room of about 400 orthotropus ovules, axile placenta and crassinucellate integument. Axial epidermal cells differentiated to archesporial cells, which multiplied by means of periclinal division and developed into peripheral cells and sporogenous cells.The sporogenous cells functioned directly as megaspore mother cells, and later underwent meiosis twice and developed into linear tetrad,to form tetrads after two, and four lanes are arranged in linear. Megaspore in the chalazal end developed into functional one. The formula of Embryo sac development belonged to variable Polygonum-type.(3)Properties of flowering and bearing. The florescence of L. pinciana population ranged from late April to late December. The flowering phase of single flower in one inflorescence, different inflorescences in one plant, different plants among one population always overlapped, which maximized the possibility of pollination success.Mature period was inconsistent between fruits derived from different florescence flowers, which was shorter in early blooming flowers and longer in late blooming flowers.However, there was at no significant difference about seed germination between the two fruit types.(4)Compatibility of interspecific cross.Except for pin flowers between L. pinciana and L.yunnanensis, the other combinations among positive and negative hybridization were all compatible. The course of incompatibility lay in that with growing of the pollen tubes, the tip of which swelled gradually and difficult to enter into the style.(5)Seed germination characteristics.By soaking in GA3 solution with the concentration of 100 mg-L-1 for six hours, seed germination rate, germination force and germination index of L. pinciana were remarkably improved;the process of germination was also facilitated.The cumulative temperature for seed germination was 260～365℃.Seed germination rate arrived at its apex when the temperature was 15℃.However,25℃should be more suitable if it was applied to practical operation. The mixture of peat soil,perlite and vermiculite (2:1:1 ratio by volume)was the best substrate for seed germination, and seedlings should be fertilized timely after seed germination accomplished.Illumination was not the determinant factor for seed germination, whereas it comes to practical operation, double layers of shading net with 50 percent shading rate should be adopted in order to avoid seed dehydration caused by intense illumination.