A Preliminary Study On Reproductive Biology Of Three Wild Orchids In Fujian Province

Fujian has rich wild orchid resources. At present, the researches mainly focus on the background investigation and flora analysis of Orchidaceae in our province, while in-depth researches on the related field of reproductive biology are rarely mentioned. Therefore, we conducted a field investigation, the process of blossom, emasculation, bagging and artificial pollination, biological characteristics and the tissue culture condition of seeds, studied the habitat characteristics, flowering character, pollen viability, stigma receptivity, breeding system of Dendrobium moniliforme, Microtis unifolia and Liparis bootanensis. The results can not only add the basic information of reproductive biology in Fujian, but also provide a scientific proof for the conservation of the above three wild orchids. The results were as follows:1. The reproductive biology of Dendrobium moniliformeThe population of Dendrobium moniliforme comes into bloom from May to June and the flowering span among populations is 20-23 days in the Youxi, Sanming. The life span of one single flower is approximately 7-16 days which in average 10.85 days. The stigma receptivity and pollen viability would exist 10 days and pollen viability was high (57.88%) in the first day of bloom time. So, we can take in artificial pollination experiments in this time which can improve the rate of fruit set.Based on emasculation, bagging and artificial pollination studies, the results indicated that Dendrobium moniliforme is self-incompatible and there is no spontanopus autogamy and apomixis. The fruit set rate of cross-pollination was more than 85%, suggesting that the breeding system is pollinators depended. Lacking of pollinators leads to the low fruit set rate which was only 1.03% or less in natural conditions. The different treatments of pollination on seeds vitality suggest that the percentage of viable seeds in nature populations (90.84%) was significantly higher than artificial cross-pollination (76.29%) and heterogeneous (76.93%) pollination (p<0.05), but the difference between the activity of heterologous pollination and artificial cross-pollination was not significant (p>0.05).So we focused on the seed nonsymbiotic germination of Dendrobium moniliforme.The results showed that the appropriate sterile germination medium of Dendrobium moniliforme is 1/2 MS+NAA 0.2 mg·L-1, the optimal medium for proliferation is 1/2 MS+NAA 0.2 mg·L-1 and the concentration at 0.2 mg·L-1 NAA or 0.4 mg·L-1 IBA on 1/2 MS culture medium is the best hormones concentration to induce root.2. The reproductive biology of Microtis unifoliaMicrotis unifolia is one of orchids in low altitude and often occurs as dense patches.The population comes into bloom from March to May and the flowering span among populations is approximately one month. The life span of one single flower is approximately 5.20 days. The pollen viability was highest within two days of bloom time. The difference between the first day (93.63%) and second day (87.91%) after flowering was not significant (p>0.05). The pollen viability would exist in 4 days until the 5 days after flowering was over. The stigma receptivity was highest in the first day and would exist in 4 days.Based on the results of emasculation, bagging and artificial pollination studies, Microtis unifolia is self-compatible and can't self-pollinate autokineticly nor has a syngamy. The breeding system is pollinators depended. The field observation found that three kinds of visitors. Two kinds of ants and certain fly which are not identified. It is exclusively pollinated by the bigger ant, but the fly has to be confirmed by continuous observation. Ant pollination process is as follows:the labellum, petals and sepal of Microtis unifolia together constitute a path for the ants to find nectar on the base of the labellum. While an ant arrived at the base of the labellum, it can touch the anther cap and withdraw the pollinia until raised its head upwards. Pollinia were often attached to the top of the ant head by the stipe from the pollinium.When it visit other flowers, carrying pollen on the stigma to complet the pollination process. Ants forage persistently, visiting individual flowers and inflorescences repeatedly for nectar which can increase the chance of pollination. The visiting pattern most likely result in self-pollination and geitongamy pollination which will lead to population decline. The low percentage of viable seeds is only 32.93% under the natural conditions. As a result, the reproductive strategy of Microtis unifolia mainly propagated by vegetations.3. The reproductive biology of Liparis bootanensisLiparis bootanensis grows in the trunk of the shadow of wet rock and a cliff valley. The population comes into bloom from November to January and the flowering span among populations is approximately 28 days. The life span of one single flower was approximately 9 days. The stigma receptivity and pollen viability were highest in the first day after flowering. But the pollen vitality in the bloom time was very low, the first day was only 36%, which may be related to the culture liquid is not suitable for pollen germination.The fruit set of selfing pollination and crossing pollination were more than 70%, suggesting that Liparis bootanensis is self-compatible, and can self-pollinate autokineticly. Self-pollination mechanism is likely to change the angle with the horizontal line as the column. With the blossom of the flowers, the angle will be increased. The narrow wings sag and the edge of the central column, forming a natural "slide". The rostellum degradation and external factors such as wind blowing or ants crawling have effects on the pollen. With the help of the gravity, the pollen can slide into the stigma to achieve self-pollination.The percentage of viable seeds in nature populations was significantly higher than artificial pollination (p<0.05), and the activity of crossing pollination was also higher than selfing pollination, CK and bagging treatment (p<0.05). The high percentage of viable seeds in nature populations (86.80±2.62%) suggests that high germination rate of Liparis bootanensis which leads to more seedings.The article is only preliminary results which needs further observation. Because of limitation of conditions and lack of research time, part of the experimental data is incomplete.