Study On Reproductive Biology Of The Rare And Protected Plant—Magnolia Dawsoniana

Magnolia dawsoniana(Family:Magnoliaceae; Genus:magnolia) is a kind of lofty deciduous leaf arbor. Magnolia dawsoniana originates from Daduhe river valley region in the middle of Sichuan Province. Because of its small population size and weak self-reproduction ability, Magnolia dawsoniana was listed in the conservation priorities by Forestry Department of Sichuan Province.Reproduct is so important for reproduction that researches on the rare and endangered plants is imminent. Therefore, this thesis tries to analyze the reasons for its small population size and endangerment statement throught reseach the flowering process, flowering phenology, growth of male and female flowering, pollination, fruit and seed characteristics of Magnolia dawsoniana in Liziping natural reserve. The main results were summarized as follows:1. The flowering process can be divided into 5 stages, namely the bud period, first blooming period, petal unfolding period, full blooming period, fading period. The blooming of Magnolia dawsoniana lasts 2-4 months, individual flowering lasts 34-42 days, group flowering lasts 43-48 days. Different altitude will lead to the difference in blooming date.2. There is the secondary opening and closing phenomenon, which means a single Magnolia dawsoniana unfolds the petal and later closes its petal at night. The next day the flower will unfold once again at around 10 am. After that it will remain unfolded and will never close until it fades.3. Magnolia dawsoniana has shown a dichogamous phenomenon, the pistil ahead of stamens mature about 12 hours. Over time, the vigor of pistil and stamens both decreasing. However,the time of pollen germination increasing. Magnolia dawsoniana has large pollen amount, the largest amount could reach 2,047,500. It has been measured that the average ratio of pollen and ovule is 2,6546.19, which is Obligate xenogamy, which means its need pollinators.4.There are only a few insects will visit Magnolia dawsonian, among which are bee, fly, coleoptera, culacidae, thripidae. The frequency of flower visiting by those insects is not high. Frequency of insect visiting varies from different factors, include the color of the petal, the smell, the pollen and the nectar. Pollen has shown a great influence towards bee, fly, coleoptera.5. Bend aggregate fruit resulted from the growth failure of carpels is quite common. Meanwhile, the rate of seed setting just 58.57%, and the rate of full seed just 46.33%. Full developed seeds, according to a test of vigor power, show an average vigor power of 60.67%. Besides, the inner and outer skin of Magnolia dawsonia has limited effect on water absorption.