Morphological characteristics of allergenic pollen from 22 commonly used spring-flowering street tree species
Tree pollen is the most common allergenic pollen in China and one of the most important causes of allergies induced in humans during spring.To reveal the individuality and commonality of allergenic pollen shape,pollen morphology studies were carried out on 22 spring-flowering street tree species with allergenic pollen widely planted in Chengdu City.Allergenic pollen was observed and measured using a light microscope and scanning electron microscope.To compare the similarities and differences in the morphology of allergenic pollen,the size index(SI)was analyzed using principal component and cluster analyses.Results showed SI values of allergenic pollen from the 22 tree species arranged from 13.43 pm to 51.10 μm,and small and moderate-sized pollen together accounted for 94.45％of the total.The pollen of Taxodium distichum var.imbricatum and Pinus massoniana had the largest variation in individual size,whereas the pollen of Pterocarya stenoptera had the most stable individual size.Pollen shapes of the 22 allergic tree species were predominantly prolate(45.45％)or subspheroidal(36.36％).Juniperus formosana was the only species in which the pollen was spherical.72.73％of the pollens belonged to the equipolar type.Among the 22 allergenic pollens,16 pollen have apertures,of which more than 50％are tricolporate type.The exine sculpture of allergenic pollen varied greatly,with mostly vague and sparse granulata(36.36％)and verrucose(27.27％)sculptures;none of them had obvious secondary sculptures.Principal component analysis and cluster analysis of pollen morphology showed that the pollen of Ginkgo biloba,J.formosana,and Casuarina equisetifolia had the most specialized shapes.The pollen shapes of Morus alba and Broussonetia papyrifera in the Angiospermae were most similar to those in the Gymnospermae.In conclusion,the 22 allergenic pollen grains were highly evolved,and their shape features tended to be characterized by small and round shapes,low dispersal resistance,and a high percentage of the tricolporate type.These common characteristics of allergenic pollens may provide a sporological basis for the preliminary identification of allergic risks in garden trees.
street treespollen morphologycommon characteristicspollen allergy
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