| The impact of global climate change on terrestrial ecosystems is becoming increasingly evident.The study of the response mechanism of plant phenology to climate change,which is regulated by environmental factors such as geographical location,has become one of the important issues in ecological research today.Climate change caused by changes in longitude and latitude will significantly affect changes in crops and their growth cycles,ultimately affecting the structure,function,and diversity of ecosystems.Bermudagrass(Cynodon dactylon)is a widely used and resistant warm-season turf grass in China.It belongs to the perennial herbaceous genus Cynodon of the subfamily Gramineae.The cuticle wax covering the leaf surface plays an important role in protecting plants from biological and non Biotic stress.Understanding the change mode of plant leaf cuticle in response to its growth environment can help us to understand the adaptability of plants to climate changes in different latitudes and longitude.In order to study how the longitude and latitude environment affects the wax structure and chemical composition of the cuticle of bermudagrass leaves,this study analyzed the response of bermudagrass leaves to different longitude and latitude environments by measuring the leaf morphological characteristics,cuticle structure,wax content and components,and leaf related biochemical indicators of 25 bermudagrass populations with different longitude and latitude gradients.The main research results are as follows:(1)On the latitudinal gradient,there was a significant positive correlation between the leaf thickness near the vesicular cells,the thickness of the upper cuticle,and the thickness of the mechanical tissue of bermudagrass leaves of different populations and latitude(P<0.05);On the longitude gradient,there was a significant positive correlation between the thickness of the leaves and the thickness of the lower stratum corneum adjacent to the vesicular cells in different populations of bermudagrass and the longitude(P<0.05).Pearson correlation analysis showed that there was a significant positive correlation between leaf thickness and annual precipitation,annual temperature and drought index in bermudagrass populations at different latitudes(P<0.05);There was a significant positive correlation between the mechanical tissue thickness of leaves of bermudagrass populations with different longitudes and annual precipitation and drought index(P<0.05).Therefore,environmental changes caused by latitude and longitude do have an impact on the anatomical structure of bermudagrass leaves in different populations.(2)Through scanning electron microscope observation,it was found that there was no significant difference in the shape of wax crystals in leaves between different populations of bermudagrass,but with the change of longitude and latitude,the arrangement density of wax crystals changed significantly.Compared with high latitude areas,the wax crystal density of bermudagrass leaves in low latitude areas significantly decreased;Compared with high longitude areas,the wax crystal density of bermudagrass leaves in low longitude areas increased significantly.Some areas on the leaves of bermudagrass populations in low latitude regions(such as Zhongshan and Guangzhou)and high longitude regions(Lianyungang and Tancheng)are not even covered by waxy crystals.(3)Five waxy components,including alkanes,esters,olefins,aldehydes,and primary alcohols,were identified from bermudagrass leaves by GC-MS(Gas Chromatography Mass Spectrometry).Esters and alkanes are the main compounds in all populations.Pearson correlation analysis showed that there was a significant positive correlation between total wax coverage,alkane,ester content,and environmental factors(annual average temperature,annual precipitation,drought index,and latitude)on the latitude gradient(P<0.05);However,there is no strong correlation between waxy component content and environmental variables on the longitude gradient.The wax crystal structure of bermudagrass leaves from different populations varies greatly with latitude,including wax crystal arrangement density,wax content,and wax chemical composition.Based on the above results,we found that latitude changes have a greater impact on bermudagrass leaves than longitude changes,which may be due to significant differences in environmental factors on the latitude gradient.(4)Based on further analysis of the relevant physiological and biochemical indicators of leaves at different latitudes,the results showed that the relative electrical conductivity of leaves increased significantly with the increase of latitude(P<0.05);The activity of antioxidant enzymes decreased significantly with the increase of latitude;The contents of MDA(malondialdehyde)and O2·-(superoxide anion)gradually increase with increasing latitude.Linear regression analysis showed that the activities of SOD(superoxide dismutase),POD(peroxidase)and CAT(catalase)were significantly positively correlated with annual average temperature,annual precipitation and drought index(P<0.05),while the relative conductivity and MDA content were significantly negatively correlated with annual average temperature,annual precipitation and drought index(P<0.05).These results indicate that the population of bermudagrass in high latitude areas(such as Cixian and Huixian)produces a large amount of free radicals in bermudagrass due to low annual average temperature and annual precipitation,resulting in membrane lipid peroxidation and activation of the antioxidant enzyme system,which can remove peroxides and free radicals,protect cells from damage,and alleviate stress effects.In summary,the differences in environmental factors caused by latitude changes significantly affect the anatomical structure,wax component content,and physiological and biochemical indicators of bermudagrass leaves.This conclusion provides a theoretical reference for the stress resistance and ecological adaptability of bermudagrass. |
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