| Plant reproductive ecology is a branch of science that focuses on the behavioral process of plant reproduction and generation and the interactions with the environment.The main research contents include the processes of plant flowering,pollination,reproductive system and fruiting,as well as reproductive allocation.It is one of the most popular fields formed during the rapid advancement of community ecology and has become one of the hot disciplines in ecological research.The Tibetan Plateau,as one of the crucial regions with the most complex ecological environment and unique biodiversity in the world,is characterized by such environmental characteristics as high average altitude,large temperature difference between day and night,strong radiation,low temperature,strong wind and dry climate.Compared with other regions in China,there is a unique natural environment in the plateau region and relatively few studies on the reproductive ecology of plateau plants.Currently,most studies are confined to species with relatively large corolla diameters that are conducive to the research on reproductive ecology.There are few studies and little understanding of differences in the reproductive ecology of alpine plant relatives with relatively small corolla diameters.In this study,the flowering phenology,pollination,breeding system and resource allocation of 3 related species Gentiana pseudoaquatica,Gentiana simulatrix,Gentiana leucomelaena of Sect.Chondrophylla on alpine meadow in Lhasa valley were studied.As per the study of the comprehensive characteristics of the flower and the flowering phenology of three species of Gentiana,there was no significant difference in the diameter of the corolla opening(p>0.05);while there are significant differences in the length of stamens,anthers,and petals(p<0.05).There was no significant correlation between the comprehensive structural characteristics of each flower of G.pseudoaquatica and altitude(p>0.05).There was no significant difference in the duration of blooming stage,the days of full-bloom stage and the average number of days of the single-flower flowering stage among the three species(p>0.05).The study on the breeding system of three species of Gentiana indicated that the pollen vitality and stigma receptivity of three species of Gentiana were basically the same with time.The pollen vitality remained at a very high level in the first 48 h,after which there was an obvious downward trend.The change rule of stigma receptivity with time was opposite to pollen vitality,which remained at a very low level in the first48 h,after which there was an obvious upward trend,with the maximum value at 72h.There was a significant difference in the P/O values of three species of Gentiana.The P/O value of G.leucomelaena was significantly higher than that of G.pseudoaquatica(p<0.001)and G.simulatrix(p<0.05),and that of G.simulatrix was significantly higher than that of G.pseudoaquatica(p<0.01).The seed setting rate of G.pseudoaquatica with emasculation and without bagging was significantly lower than the natural seed setting rate(p<0.05),which indicated that it had a higher selfpollination rate;The seed setting rate of G.simulatrix and G.leucomelaena with direct bagging was significantly lower than the natural seed setting rate(p<0.05),which indicated that they had a higher outcrossing rate;The seed setting rate of G.leucomelaena and G.pseudoaquatica treated with artificial pollination was significantly higher than that of natural seed setting rate(p<0.05),which indicated that they were limited by pollen in the natural state.The seed setting rate of the three species of Gentiana after corolla removal was significantly lower than the natural seed setting rate(p<0.05),which indicated that the corolla played a crucial role in the pollination and seed setting process of them.The OCI values of three species of Gentiana were 5.As per the P/O value,bagging experiment and OCI value,it could be concluded that the breeding system of G.pseudoaquatica was facultative self-pollination and self-compatibility,and sometimes pollinators were required;The breeding system of G.simulatrix and G.leucomelaena was facultative outcrossing and partial self-compatibility.According to the observation and recording of flower-visiting insects,it could be concluded that there were 7 species of flower-visiting insects recorded in G.pseudoaquatica and G.simulatrix respectively,and 8 species of flower-visiting insects recorded in G.leucomelaena Among them,there were 5 common species of flower-visiting insects,including 1 species of Formicidae,2 species of Syrphidae,1 species of Anopheles,and 1 species of Lobesia reliquana.The most effective pollinator to visit the three species is ants,and the visit time for the single flower of G.leucomelaena was significantly higher than that of the other two species(p<0.05).Syrphidae had no preference for three species of Gentiana.The results of resource allocation patterns showed that there was no significant correlation between reproductive allocation and altitude(p>0.05),and nutrient allocation and altitude(p>0.05)for both G.pseudoaquatica and G.simulatrix;The sexual allocation of G.simulatrix increased significantly with the increase of altitude(p<0.05),while there was no significant correlation between the sexual allocation and altitude for G.pseudoaquatica(p>0.05).There was no significant correlation between reproductive allocation and aboveground biomass(p>0.05)in the four altitude zones and the overall level of G.pseudoaquatica and G.simulatrix,which indicated that the reproductive allocation of the two species did not show a dependence on individual size;There was a significant negative correlation between the sexual allocation and the aboveground biomass for G.pseudoaquatica at 3800 m,4020m and the total level(p<0.05),and the other two altitude sample also showed a downward trend,which indicated that the sexual allocation of it had a dependence on individual size;There was no significant correlation between the sexual allocation and the aboveground biomass for G.simulatrix in four altitude zones and the total level(p>0.05),which indicated that the sexual allocation of it had no dependence on individual size. |
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