| Artemisia wudanica is mainly distributed in Wengniute Banner and its surrounding areas in the western part of Horqin Sandy Land.It is born on mobile and semi-mobile fixed dunes and is a semi-shrub of Artemisia genus.As a pioneer plant for windbreak and sand fixation,it has very important ecological value in the desert area.In this study,Artemisia wudanica was used as the test material,and studies on ecology,soil science,soil chemistry,cytology,cell biology,and pollen science were used.Methods:A special study was conducted on the problems related to ecological degradation,such as population structure,seed germination,and pollination characteristics,to interpret the population structure,seed germination,and pollen spreading rules of A.wudanica,and to reveal the causes of ecological degradation of A.wudanica.The findings are as follows:1.The height,crown width and base diameter of the A.wudanica on the sunny slope were the largest,and the height and base diameter A.wudanica on the shady slope were the smallest.The crown width was significantly higher than that of the semi-sunny slope and the semi-shady slope.There was a quadratic polynomial relationship between the plant height and crown width of the sunny slope and semi-sunny slope.The plant height and crown width of the semi-shady and shady slope were linearly related.The plant heights of semi-sunny slope,semi-shady slope and shady slope were significantly positively correlated with crown width,base diameter,and age.On sunny slope,semi-sunny slope,and shady slope,Artemisia belonged to random distribution,and the semi-shady slope belonged to cluster distribution.2.The variation range of soil C content was 0.3-0.57g/kg,soil N content was between 0.04-0.12g/kg,and soil P content was 0.12-0.24g/kg.The N,C:P and N:P of leaves of A.wudanica gradually decreased from the sunny slope to the shady slope,soil C,C:P and N:P gradually increased,soil P and soil C:N were in different slope directions.There was no significant difference.There was a significant positive correlation between P and root P of the leaves of A.wudanica,and P of leaves and roots were significantly positively correlated with C:P and N:P.The content of C and N in leaves decreased with increasing soil nutrient content.The contents of P and root N and P in leaves increased with increasing of soil nutrients.The correlation between leaf C and C:N and soil was greater than root,and the correlation coefficient between leaf P and N:P and soil was smaller than root.Different slopes had the best growth on the shady slope,and the slope direction had an important influence on the growth of A.wudanica.3.There was a very significant negative correlation between the maximum temperature and the leaf Pro content and root ABA content,the correlation coefficients were-0.738 and-0.795;the light had a very significant positive correlation between leaf MDA content and root IAA,the correlation coefficients were 0.651 and 0.796,the light had extremely significant negative correlation with leaf CAT,leaf GA3,leaf ZR,root CAT,root GA3,the correlation coefficients were-0.810,-0.740,-0.779,-0.759,-0.717;There was a very significant positive correlation between soil C and root SS,with a correlation coefficient of 0.831;soil N content had a very significant positive correlation between leaf POD and root POD,the correlation coefficients were 0.733 and 0.730;and a significant negative correlation with leaf IAA,the correlation coefficient was-0.817.4.The optimum seed germination of A.wudanica was under the constant temperature treatment at 25? and 12 light/12 dark treatment.With the increase of PEG treatment concentration,the daily relative germination rate of A.wudanica showed first increase and then decrease,concentrated on the 3d and 4d germination.The germination potential,germination index,vigor index and drought resistance index decreased significantly with the increase of drought stress concentration,saline-alkali stress concentration and pH value.The relative injury rate increased from 4%to 96%,and the radicle and germ length were long.Both showed a downward trend with the increase of PEG concentration.Saline-alkali stress had a strong inhibitory effect on the germination of A.wudanica seeds.5.The results showed that there were obvious dimorphic characteristics of the pollen morphology:a long spherical shape and a spherical shape.The pollen had.The size of long spherical shape was 23.28 ?m×13.73 ?m in average,the polar axis/equatorial axis ratios was 1.70 and the size of spherical shape wasl4.85 ?m×13.80 pm in average,the polar axis/equatorial axis ratios was 1.08.Except for pollen size,polar axis/equatorial axis ratios(P/E),the overall morphological characteristics of long spherical pollen and spherical pollen were basically the same,the main differences in subtle traits were the size of thorns in the surface texture and the arrangement density of thorns and particles.6.On the 3rd day after flowering,the pollen vigor was the highest,and on the 3rd day after flowering,the stigma was the most receptive.The highest period of pollen vigor and the best period of stigma receptivity occured at the same time.It was a wind-pollinated cross-pollination plant.The highest number of pollen grains were captured in the horizontal and vertical directions from 12:00 to 14:00,and the total amount of pollen grains can reach 741.In 24h,the pollination efficiency of A.wudanica was positively correlated with meteorological factors such as temperature and wind speed and it was negatively correlated with relative humidity.In summary,the root cause of the internal factors of the decline of the population of A.wudanica was mainly in the fertility and viability.Under extreme drought and high temperature conditions,the conversion rate of seeds to seedlings was extremely low,the number of seedlings formed was small,and the population was difficult to maintain.Due to the narrow distribution area,lack of gene communication and long-term degradation of habitat,the physiological and ecological adaptability of A.wudanica decreased gradually.The extrinsic factors were due to the decline of habitat carrying capacity,the loss of population viability,the decline of genetic diversity,and the combination of external environmental factors and internal unfavorable factors led to the decline of the population of A.wudanica. |
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