Analysis On The Pollination Characteristics And Factors Effecting The Seed Yield Of Alfalfa In Pollination

With the aid of pollination biology and reproductive ecology methods, the biological characters such as the pollination ecology, cross-fertilization mechanism, breeding system,the dynamics of biomass allocation,patterns of fruit and seed production,seed yield and agronomical traits etc. of Medicago varia Martin.cv.Xinmu No.1 plant of varied growth fixed number of year and the factors effecting seed yield of alfalfa in pollination have been studied from 2004 to 2005. The main results are as follows:1. There are distinctive flowering behaviors and tripping phenomena in different phase of alfalfa abloom and between varied years. In 2004, the first florescence of three-year-old alfalfa plant, the raceme took about 4～7days for all florets to bloom. After blooming, the floret lasted 4～7days before wilting, and not tripping itself for the keel petal of floret. At anthesis, each raceme took about 1～4days for all florets to bloom. The life-span of flower was 2～4 hours. After blooming, the flower tripped itself in 1～2 hours and then wilting in 1～2 hours. The distinct difference of flower life-span in different phases of florescence is relat to tripping. The flower will wilt in several hours after the keel petal flicking out, and it could keep on opening for a week if the keel petal of flower is not be flicked out or flicking out itself. The tripping depends on the weather conditions, temperature and illuminance are important factors effecting tripping.2. At anthesis, a flower could provide 0.1～0.5ul/d×3～5d of nectar,3509.3±299.12 pollen grains. The incidence of pollen grains abortion was 40.48±2.3%. The mass insects visiting occur at anthesis. The average density of the main pollinators was 3～5/m2. The average visitation rate of flies as the main pollinators was 2.1 per raceme per day. The traits lead to lower pollination efficiency ,such as limited floral rewards, the higher incidence of pollen grains abortion, and the strict selectivity to pollination insects . Because of the weather conditions, the tripping efficiency of visiting insects have a great difference between varied years. When the pollination insect is no use for tripping , whether the florets can trip or not themselves and the tripping phase are the key factor effecting the alfalfa seed yield.3. The study on the fluorescence observing of pollen germination and pollen tube growth rate after artificial pollination , the stigma vitality and the clogging of self-pollen to stigma have shown that there were two mechanisms to prevent alfalfa from self-fertilization by...