Study On Pollination Biology And Aseptic Seeding Of Calanthe Striata R.Br.

Calanthe striata has high ornamental value for unique flower apperance,bright yellow color,fresh and elegant plant shape,and so on,but the number of the plants in the field was very small,so it was classified as "minimal population conservation species" in China.In this study,we studied the pollination biology and aeptic seeding of C.striata by using plots survey,field observation and other methods to explore the characteristics of the flowering phenology,breeding system,adaptability of pollinators and insects,the rules of aeptic seeding technology,with a view to provide scientific basis message for the scientific strategy of protecting and developing the resources of C.striata and other wild orchid,and strengthen the protection of the in situ conservation in situ.The results showed:Belonging to the dense flowering type plant with bright yellow flowers,C.striata began flowering in April 15 to May 13,continued for 29 days;the flowering duration of population was 23.92 days;the flowering duration of individual was 20.22 days;and the flowering duration of the single flower was 19.30 days.The average of flowering index of C.striata population in China was 0.787,with relatively concentrated flowers.The flowering curve was unimodal and bloomed only once a year.The color of different parts of flowers was similar,different categories of yellow series,and similar colors changed as it withered.Flower had nectar guide,without nectar,had aroma in sunny day.The volatile components were analyzed by GC-MS.We found methyl benzoate and so on.The best combination of pollen culture medium for testing pollen viability was:30 g·L-1 sucrose+60 mg·L-1 boric acid+15 mg·L-1 calcium nitrate.The first day of flowering to withered activity,with the flowering time,activity decreased.The first day of open and post-flowering stigma were acceptable,the first day of the best activity.Outcrossing index was 4,the pollen-ovule ratio(P/O)was 16.05 to 32.23 and the average was 23.39±1.87.High self-compatibility,no automatic self-pollination,possible apomixis,the success rate of self-pollination and hetero-pollination were both 100%,but there was abortion at the later stage after pollination,the rate of self-pollination was the highest and the decline of inbreeding was obvious.The Bombus sp.,a kind of large bumblebee,was an effective pollinator for C.striata.Belonged to the food deceptive pollination mechanism,C.striata mimesis with Pittosporum illicioides,a homozygous plant which flowering in the same period with similar color and aroma to attract the bumblebee.The broad head height of the bumblebee are slightly larger than those of the flower.With magnificent obvious inflorescence,spur,yellow fake nectar guide and aroma signal,C.striata attractted the Bombus sp.to visiting the flowers.When the bumblebee reached out its beak to gather honey from the flower,the pollen lump was stuck to the head of the bumblebee.When the next flower was visited,the sticky stigma transfered the pollen to its stigma.The Bombus sp.heads were slightly wider than the flowers,when visiting the flower,inserting its proboscis deeply into the spur,its head was pushed against the column,then receiving or deposit pollinaria.The perfect morphological matching between flower and bees made it reproductive success.In 2016,pollen removal rate was 13.99±1.60%andpollen deposition rate was 23.36±2.14%,and the seed setting rate was 5.88±0.85%.In 2017,the pollen removal rate was 11.14±1.39%,and the seed setting rate was 4.60±0.76%.The seed germination of C.striata was 120 days:the powdery seeds absorbed water and gradually became bigger and turned colorless.After a period of time,the seed embryo began to break the seed coat,then turned green.Protocorm grew bigger and bigger,plant growth and prosperity.The experimental materials had lowest rate of seed pollution after 75%alcohol disinfection for 30 seconds,10%sodium hypochlorite disinfection for 15 min.The best medium for seed germination medium was selected as 2 g·L-1 Hyponex No.1+1/2 MS medium+0.37 mg·L-1 MgSO4·7H2O+25 g-L-1 Sugar+1 mg·L-1 6-Benzylaminopurine+0.2 mg·L-1-Naphthaleneacetic acid+1 mg·L-1 Kinetin+5.5 g·L-1 Agar+1.5 g·L-1 Activated carbon powder+2 g·L-1 Beef extract peptone+50 g·L-1 Onion,the pH was adjusted to 5.7～5.8.The basic research on pollination biology and aseptic seeding of C.striata can help us to understand the biological characteristics,the flowering phenology,pollination mechanism and possible endangered mechanism,thus providing the basis information for the conservation in situ and ex situ protection and in vitro of this species.