| C. praecox(L.) Link (Calycanthaceae), is a deciduous shrub or small tree, and an endemic plant of China. Compared with other species whose florescence is earlier than its, blooming in winter, C.praecox is special in its pollination time and process. This paper firstly focused on and evaluated the pollination characteristics of C. praecox, in half-natural habitat of Nanjing. We investigated flowering phenology, flowering patten, pollen viability, stigma receptibility, species of visitors, visiting rate of visitors and their foraging behavior. And we also investigated its breeding system, including pollen-ovule ratio(P/0), out-crossing index(OCI), pollen grains deposited in stigmas, pollen germination rate and seed set rate with different treatments, from 2002 to 2004. We compared the pollination characteristics of C. praecox and that of C.nitens.The results are as follows:(1) The main variation of C.praecox exists in the floral morphological characteristics, including the variation of the color of the interior perianth segments, the color and shape of the middle perianth segments, the number of pistils and stamens, the length of pistils and degradation of stamens, the floral shape and size, etc.. C. praecox's florescence is from November to next March, mainly from December to next February. The floral characteristics of C. nitens are less varied, and its florescence is from September to December in Nanjing. A great number of and sweet scent of flower of C. praecox are attractants, and pollen grains and nectar of it are rewards to vistors.(2) Pollen viability of different varieties of C.praecox are distinctly different. The life-span of pollen is 15 to 20 days under room condition and 2 months under 4+2C; The life-span of receptive stigmas is 5 days. In spite of protogyny, the meeting time of life of effective pollen and stigma of two species are respectively 2 days and 0. 5 day.(3) The value of P/0 of C.praecox is 2847.3+1125.0, and the total value of OCI is 3. With the above results, pollen germination rate and seed set rate, all shows that breeding system of C. praecox is facultative hybridization. Thebreeding system of C.nitens is similar to C.praecox, but it is higher in proportion of self-pollination than that of C. praecox.(4) Fluorescent investigation shows that pollen started to germinate about 20 hours later after deposited on the stigmas, only 1 or 2 pollen tubes can penetrate ovary to micropylar end on the fifth day. Callose plugs evenly formed in the pollen tube, and sometimes callus deposited randomly along pollen tube wall and even the whole tube wall.(5) 16 species of insects visited C.praecox in Nanjing, belonging to Hymenoptera,Diptera, Coleoptera, Thysanoptera and spiders(Arachnoidea); Apis cerana cerana Fabricius,Aldrichina grahami(Aldrich),Epistrophe balteata De Gee, Musca hervei Villeneuve are its main efficient pollinators. The main visiting insects of C. nitens in Nanjng are beetles. Because Beetles originated earlier than Bees and Flies, so in this aspect C.praecox is more evolutional than C.nitens. Insects visited C.praecox only in the sunny days and when the highest temperature of day is higher than 10C, their visiting time is from 10:00 to 14:00 in a day, and its peak is from 12:00 to 13:00.(6) The effect of wind to spreading pollens of both species is little.
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