| Agapanthus belonged to monocotydoneae,Asparagales.Its original species occurred in South Africa.Agapanthus praecox was an evergreen species in Agapanthus.According to the data from the field observation,we studied the characteristics of reproductive biology of A. praecox ssp.Orientalis 'Big Blue' including floral syndromes and breeding system,flowering biotemperature and pollination mechanism,biomass dynamic and reproductive allocation,seed setting pattern and seed setting limiting factors,seed development process and seed germination characteristics,effects of shading on leaf structure and photosynthetic characteristics and so on.All the research putted in practice at WuShe practice base in Shanghai Vocational Technical College of Agriculture & Forestry,Shanghai,China.1.Breeding system:In artificial populations in Shanghai,the individual flower longevity was 2 to 3 days and individual inflorescence duration was about 15～30d.Stigma had receptivity since the next day of flowering.On the day of flowering,the styles were shorter than the filaments.Spatial positioning of stigma and anthers was spatially desperation.Stamens and pistils matured asynchronous.There were not peaks in individual inflorescence duration and there were a certain amount of opening flowers per day.The total value of OCI was 4 and the value of P/O was 25622.The seed setting ratio with different treatments showed that its breeding system can be determined as outcrossing with partly self-compatible and needed pollinators during the pollination.2.Though calculating relative flowering intensity and synchrony indices we analyzed the influence of flowering phonology to reproduction.The results showed that the flowering span of population was May to July in Shanghai.Population duration was about 40d.The census date of flowering phonology was late 7～9d from 2007 to 2008.The curve of open flowers proportion showed two major peaks.The synchrony indices of two years were 0.663 and 0.695 and it showed that the time of florescence overlap was long。The correlation analysis among onset,duration,flowers and fruit set showed marked relations.There were significantly negative correlations between onset and flowers,fruit set and duration.On the other hand,there were significantly positive correlations between flowers and fruit set,duration.The individual with an early starting date showed a longer duration than the individual with a later starting date.The individual with more flowers showed a longer duration than the individual with less flowers.At the same time,the individual with a longer duration showed a higher fruit set than the individual with a shorter duration.As a exotic plant,the similarity of flowering phonology within two years suggested that A.praecox ssp. orientalis 'Big Blue' can adapt to the environmental pressure and exhibited a steady flowering onset date and flower pattern.The longer florescence overlap and mass flowers may be regarded as an advantage to attract more pollinators and ensure its reproductive success.3.During 2007 to 2008,a total number of 23 species of insects were recognized as the flower visitors.Among which 13 species were pollinators including Apis cerana cerana, Bombus festivus Smith,Papilio polytes Linnaeus and Pieris rapae Linnaeus.The visiting frequency was different between various insects and similar between various anthesis.Visiting frequency in one day varied distinctly.Butterflies' visiting activity mainly fastens on a.m.and bees' visiting activity was longer than others.Comparing the efficiency of pollinators,it was found that bees were much more effective than butterflies and flies.Stereoscopic microscope observation on insects' body also supported this point.Added pollen showed that the pollinators were not enough.Treatment of emasculation and perianth removal showed that the reward of nectar was more attractive than pollen to pollinators.Added pollen showed that the pollinators were not enough.Moreover,insects' visiting activities were relation to the floral display.Floral display at 10 to 15 was more effective for pollination.4.Reproductive allocation:Total biomass ascended during the anthesis and increased rapidlly at July and Augest.Biomass of nutrition organ was bigger than generation organ. Biomass allocation ratios of roots and stems descended during the anthesis at the same time biomass allocation ratio of leaves ascended after July.Biomass allocation ratio of generation organ maintained low level.The dynamic change of nitrogen and phosphorus content was:The content was higher in initial phase of flowering and then descended gradually.The change of potassium content was not significantly during initial phase of reproduction growth and then ascended markedly during maturation period of fruit.5.Seed setting and fruit setting:The order of fruit setting ratio was base of inflorescence＞center of inflorescence＞apex of inflorescence.The order of seed setting ratio was:base of fruit＞center of fruit＞apex of fruit.Seed yield was 6.67%to potential yield which indicated the actual yield below potential yield markedly and there was fairly space in yield.The opening order of inflorences was base to top and the flowers of opening early were predominant in resources obsorbtion and utilization.Therefore the possibility of fruit maturation was highest at base of inflorescence.Combining regular pattern of biomass change and conclusion of cutting leaves,flowers removal as well as fertilizer-added,we considered that there were pollen limitation and resource limitation in seed set and fruit set.6.Seed development and germination:(1)The seed length reached the maximum on 56～63d after pollination,and the mass growth increased rapidly in the first two weeks.The dry weight of seeds leveled off on about 42d after pollination.(2)Starch content accumulated rapidly at the early stage of seeds development and the trend was"up-down-up";Level of soluble protein tended to rise gradually while level of soluble sugar dropped gradually.There were remarkable positive correlations between starch content,soluble protein content and dry weight,seeds length.On the other hand,there were remarkable negative correlations between soluble sugar and starch content,dry weight,seeds length.(3)Significant changes in contents of POD,PPO and a-amylase occurred during the process of seed development.There were remarkable positive correlations between enzymatic activity of POD,PPO and soluble protein content,so as the correlation between a-amylase activity and seeds length.(4)Soluble sugar content tended to rise gradually during seed germination whereas starch content tended to rise gradually which meant starch decomposed to sugar on order to suppling seed germination. Seed germination ratio was low.This problem should be solved in breeding in the future.7.Photosynthetic characteristic:Shading(0,30%,60%,and 80%)was applied to A. praecox ssp.orientalis 'Big Blue' to determine a theoretical basis for morphological and photosynthetic characteristics.Results showed that leaf area,length of stomata apparatus, chlorophyll content increased under limited light conditions,but thickness of leaf,leaf weight ratio,chlorophyll a/b and density of stomata apparatus decreased.All of those indicated that the leaves made a quick adjustment to shading environment and changed gradually to cheliophytes.The LSP was less to 1000μmol·m-2·s-1and LCP was less to 20μmol·m-2·s-1which in keeping with indicators of shade enduring plant.Daily variety curve of net photosynthetic rate showed two peaks in full sunlight and one peak in shading condition,which indicated"noon break"occurred only in full sunlight and shading could lighten or avoid photoinhibition in strong light.Under limited light conditions,Fv/Fm and Fv/Fo higher than those in full sunlight,which meant electron transfer rate ascended.Following shading aggravated,ΦPSⅡand qP descended which meant shading limited photochemical efficiency and electron transfer activity. |
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