Invasive Biological Characteristics And Chemical Control Of Galinsoga Quadriradiata Ruiz Et Pav.

Galinsoga quadriradiata Ruiz et Pav.,an annual herb of the family Asteraceae,has invaded many provinces in China,posing a greater threat to agricultural production and the ecological environment in the invaded area.Found in Inner Mongolia Autonomous Region in 2018,but the related research was still blank.In this paper,the invasion distribution,habitat type,phenological characteristics and seed germination characteristics of G.quadriradiata Ruiz et Pav.in Hohhot was investigated.On this basis,the effect of the invasion on plant diversity in Hohhot was analyzed by sample method and mathematical statistics.The photosynthetic characteristics and invasion adaptability in different growth periods were analyzed by photosynthetic apparatus.Finally,the effective herbicide and its effective concentration were screened by the analysis of chemical control tests in different growth periods.The results of the study were as follows:1.There are a total of 67 invasion distribution points of G.quadriradiata Ruiz et Pav.in Hohhot,which are distributed in the districts and counties under the jurisdiction of the city,of which the four districts are the main distribution sites,accounting for 83.58%.The types of distribution habitats are diversified,including vegetable gardens,green belts,wasteland,etc.,mainly green belts and lawns.The growth period and flowering period are longer,the seed setting was large,the yield of single seed was 6122-24000,the seed was light and small,and has strong reproductive ability and transmission ability,which provides favorable conditions for its successful invasion.Seeds were able to germinate at 6 temperatures?10?,15?,20?,25?,30?,35??,but the difference between germination rates was significant.The seed germination rate,germination potential and germination index were all low with other treatments at low temperature?10??and high temperature?35??.The optimum temperature for germination was 25?,the germination rate was 97%,and the germination potential and germination index were the largest.At different soil burial depth?0 cm?1cm?2cm?4cm?6cm?8cm?10cm?,the emergence rate was different.When the depth was 0 cm-4cm,the difference of seed emergence rate was not significant;and the seedling emergence rate was negatively correlated with the soil burial depth.when the depth was 10 cm,the seed emergence rate was only about 10%.In the future,seeds can be buried deep through deep cultivation to control their spread and spread.2.Sample method analysis and comparison of 21 sample plots,a total of 73 wild plants,Compositae?18 species,24.66%?and Gramineae?13species,17.81%?were the main plants,there were 22 common plants;After curve fitting and statistical analysis of the important value and plant diversity index,after curve fitting and statistical analysis of the important value of G.quadriradiata Ruiz et Pav.and plant diversity index,it was found that the four plant diversity indexes were lower in the invasive area.At an important value of 0.550,the Shannon-Wiener index in the site of invasion showed a significant downward trend,When the important value was 1.101,the Simpson index,the Pielou index were significantly lower than the control,which indicated that the invasion of G.quadriradiata Ruiz et Pav.had a negative effect on plant diversity in Hohhot.3.The photosynthetic light response curves in different growth periods showed the trend of rose straight,rose slowly and then decrease;the best models for fitting the photoreaction curves were modified rectangular hyperbolic model;The daily changes of net photosynthetic rate showed a"bimodal"curve,and there was a phenomenon of photosynthetic"lunch break",which was related to stomatal factors,the mean values of daily changes were in flowering stage>seedling stage>consolidation stage.Water vapor pressure deficiency,stomatal conductance and other daily changes showed a single peak trend,water use efficiency also showed a bimodal curve.The daily changes of net photosynthetic rate were related to stomatal conductance,intercellular CO₂ concentration,photosynthetic effective radiation and other factors.The G.quadriradiata Ruiz et Pav.had higher light saturation point and lower light compensation point,which can adapt well to the change of external light and provide conditions for its successful invasion.4.In different growth period,the effect of chemical herbicide on the control of G.quadriradiata was different.In the flowering period,20%and20%fomesafen had better effect,and the plant control effect was about80%-98%;In the fruiting period,the control effect of 20%fluroxypyr was better,the plant control effect was 71%-93%;The control effect was positively correlated with the concentration and negatively correlated with the control period.Considering the effects of herbicides on the environment and other plants,it was considered that 1.25ml/L20%fluroxypyr and 0.75ml/L20%fomesafen are more suitable for the prevention and control of G.quadriradiata Ruiz et Pav.,especially for the flowering stage of G.quadriradiata Ruiz et Pav..