The Comparison Study On Reproductive Ecology Of Xanthium Italicum Moretti And Xanthium Sibiricum Patr.ex Widd

The Xanthium italicum Moretti and Xanthium sibiricum Patr.ex Widd are all annual herbs of the Compositae and Xanthium L.The X.italicum was first discovered in China in 1991.Since then,X.italicum has rapidly spread in our country.It has successfully invaded the ecological environment in various parts of China.It has a major impact on the local ecological diversity and crop yield.In 1997,X.italicum was listed as China's entry quarantine pests.Since then,many research scholars at home and abroad have studied X.italicum,but most of the research has focused on the biological characteristics of X.italicum and the distribution and prediction of suitable habitats.However,there are hardly any research trends and any reports on the reproductive ecology of X.sibiricum s.A large number of studies have indicated that the reproductive ecology of plants is of great significance to the growth and reproduction of plants,so this article explores the reproductive ecology of X.italicum and compares them with non-invasive plants of the same species,making it easy to find out reproductive ecology basis for successful invasion and spread.The experimental results are as follows:1.According to the study on the flowering phenology of X.italicum and X.sibiricum,it was found that the flowering period of X.italicum was longer than X.sibiricum at each level.In the flowering period of X.italicum,the flowering duration of male and female inflorescence was 50 days,27 days and 18 days,respectively.For the flowering period of X.sibiricum population,the duration of flowering at the inflorescence level was 45 days,17 days and 15 days.The male inflorescence amplitude curves of X.italicum and X.sibiricum are bimodal,while the female inflorescence flowering amplitude curves are all unimodal;both curves are expressed as X.italicum slightly higher than X.sibiricum,indicating that under the same period the flowering of X.italicum was more than that of X.sibiricum,so it could effectively increase the probability of successful reproduction.The flowering synchronization indexes of X.italicum and X.sibiricum were both higher.However,the female and male inflorescence of flowering synchronicity index of X.italicum flower was higher than that of X.sibiricum.Both flowering patterns are"centralized flowering pattern,"but the tendency of X.italicum flowering is more concentrated,which will significantly increase the probability of successful pollination under the same period.2.Through scanning electron microscopy of X.italicum and X.sibiricum pollen,it was found that X.italicum and X.sibiricum pollen are typical Asteraceae three-channel pollen.Pollen morphology is oblate,pollen wall is not smooth with a spiny carving.But the X.italicum pollen volume is larger than the X.sibiricum,and the pollen surface has a decoration that is also relatively rough,making the X.italicum pollen more easily adhered to the stigma than the X.sibiricum;The observation of the media found that during the entire flowering period,no insects visited the X.sibiricum flowers,whereas insects of the Wasp.sp visited the X.italicum flowers.The presence of visiting flower insects can increase the probability of successful pollination.The pollen-borne distance curves of X.italicum and X.sibiricum were all unimodal.However,the distance between the two pollen peaks was different,and the amount of pollen distributed by X.italicum was higher than that of X.sibiricum at different distances.3.From the perspective of X.italicum and X.sibiricum breeding characteristics,the all-day pollen activity exhibited by X.italicum and X.sibiricum was a single-peak curve.Both of which reached the maximum pollen viability at 14:00,but in terms of pollen vigor,the rising trend of X.italicum pollen was greater than that of X.sibiricum.It can be seen that at the same time,the pollen of X.italicum is stronger and it is easier to spread pollen successfully.Before 18:00,both plants showed high activity in Xanthium,but the pollen vigor of X.italicum was always slightly higher than that of X.sibiricum.At 20:00,pollen vitality decreased significantly.At this time,the pollen viability of X.italicum was 1.33%,and the X.sibiricum at this time was 1.08%.Experiments have shown that the X.italicum and X.sibiricum stigmas are tolerable for up to 7 days,and that the time when the stigma reaches the maximum is the 3-4th day that the stigma sticks out of the total involucrum.At six days,the stigma of the X.sibiricum was almost completely inactive,while a small proportion of the stigmas in the X.italicum population still had weaker acceptability.At the same time,when the stigma is the most tolerable,the stigma of the X.italicum extending out of the involucrum is much longer than the X.sibiricum.At this time,the stigma area of the X.italicum stigma which can accept pollen is much larger than that of the X.sibiricum.The surface area of the X.italicum stigma is 157mm~2,and the is only 110mm~2,indicating that the probability of successful pollination of X.italicum is sig X.sibiricum nificantly improved.In the experiment,the number of male and female inflorescences of X.italicum and X.sibiricum and the average number of pollen per plant were statistically analyzed.The experimental statistics showed that the average number of male and female inflorescences and pollen numbers of X.italicum were significantly higher than those of X.sibiricum.\The ratios of pollen ovules of X.italicum and X.sibiricum,as well as the results of bagging experiments,show that the two breeding systems of the Xanthium genus are self-crossing and hetero-cross hybrid systems.In summary,the X.italicum has distinct advantages over the X.sibiricum in the breeding process of the entire population.Regardless of the duration of the flowering period,the trend of the value of pollen viability,the length of the stigma to be maintained,and the acceptable area,the number of male and female inflorescences,and the number of pollen,all exhibited advantages over X.sibiricum.It greatly improved the chance of success of X.italicum breeding and provided the basis for the successful reproduction and large-scale spread of X.italicum.