| Parthenocissus quinquefolia and Parthenocissus tricuspidata belong to the family Vitis,and Hedera nepalensis is a member of the family Araliaceae,all three plants are perennial climbing plants.The three plants have low soil requirements.They can grow well in barren,arid,and dehydrated environments,play an important role in slope protection and greening.Phytolacca americana is an invasive plant belonging to the phytolaccaceae.P.americana has caused a serious threat to the diversity of local plants.To understand the similarities and differences in pollination ecology between invasive plants and native slope protection plants,reveal it invasion mechanism.Therefore,this paper conducts a comparative study on the ecological characteristics of pollination of P.quinquefolia,P.tricuspidata,H.nepalensis and P.americana in terms of flowering phenology,pollen histochemistry,pollen viability,stigma receptivity,and breeding system.It provides a basis for the prevention and control of invasive plants and the continuation of the slope protection plants.The main results are as follows:P.americana populations have longer flowering periods than P.quinquefolia,P.tricuspidata and H.nepalensis.The flowering period of P.americana was 45 d to 70 d.The temperature of the H.nepalensis flowering period is low,and the open time of single inflorescence of H.nepalensis is longer than that of the other three plants.Single inflorescence flower is fully open longer than the other three plants.P.americana has a large corolla diameter,its stigma "specialized cluster" 9 to 10 cracks.P.quinquefolia's similar to Hedera nepalensis,with a "conical" shape and a split "ditch".P.tricuspidata stigma is "cylindrical",the stigma of P.americana and P.tricuspidata is more specialized than that of the other two plants,which is conducive to the capture or placement of pollen.The pollen of P.quinquefolia and P.tricuspidata flowing with the wind,and combined with the pollen histochemistry and the stigma specialization degree,it is determined that the four plants have the characteristics of both anemophilous and entomophily.H.nepalensis is dominated by insect vectors.The pollen vitality of P.americana is higher than 85%,which was higher than that of P.quinquefolia,P.tricuspidata and H.nepalensis.The highest pollen vitality of latter three plants was no more than 60%.Combining the pollen vitality time with thestigma receptivity duration,it is believed that the latter three plants may allocate more resources to female functions during reproduction,leading to pollen immature or structural damage,which results in low pollen vitality.Pollen germination experiments were performed on latter three plants with low pollen viability.There are significant difference among pollen germination rates of P.quinquefolia,P.tricuspidata and H.nepalensis at different temperatures(20°C,25°C,30°C,35°C).Compared with other temperatures,the pollen germination rate of the latter three plants was higher at 25?30°C.Comparison of species diversity of flower visitors between invasive plants and native slope protection plants,the Margalef richness index and the Shannon-Wiener diversity index have the same trend as H.nepalensis > P.americana > P.quinquefolia> P.tricuspidata,the species diversity of H.nepalensis flower visitors is higher than that of P.americana and other two plants.The species diversity of flower visitors on P quinquefolia and P.tricuspidata is relatively low.The fruit setting ratio of P.quinquefolia is not more than 10%,and the fruit setting rate of H.nepalensis is not higher than 30%.Combining pollen vitality with pollen germination rate,it was found that most flowers of the latter three plants only played a role of attracting visitors during the reproduction process.Under natural conditions,the fruit set of Phytolacca americana is close to 100%.Based on P/O and OCI,the breeding systems of P.quinquefolia,P.tricuspidata and H.nepalensis are preliminarily determined to be self-compatible and out-crossing,and pollinators are required.And the breeding system of P.americana is self-compatibility and facultative self-breeding and require pollinators.In conclusion,the flowering period of P.americana is longer than that of P.tricuspidata,P.quinquefolia and H.nepalensis,and the stigma of “specialized clustering” is favorable for more pollens to fall on it.The pollen vitality of P.americana is as high as 85%,and the pollen vitality of other three plants is low.The pollen vitality time of P.americana is higher than that of stigma receptivity for a long time,which is conducive to the occurrence of selfing.Selfing is the guarantee for successful invasion.The pollen vitality of P.quinquefolia and P.tricuspidata is higher than the stigma receptivity,which is a breeding strategy to avoid selfing.The breedingsystems of P.quinquefolia,P.tricuspidata and H.nepalensis are mainly self-compatibility and outcrossing,and pollinators are needed.P.americana has a self-bred and outcross hybrid breeding system with high fruit set and high seed setting rate,which makes it self-bred under severe weather conditions and reproductive guarantee.P.quinquefolia can also perform outcrossing under suitable pollination conditions to increase variability and enhance the ability to adapt to the environment,so that it can quickly invade and colonize. |
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