Aims The growth and survival of plants are being threatened by more frequent extreme high temperature events under global climate change.Therefore,for species conservation and adaptability prediction,it is essential to accurately evaluate the physiological heat tolerance across plant species.Magnoliaceae,as a typical basal angiosperm lineage,is one of the representative lineages in subtropical evergreen forests in China,with high ecological and evolutionary significance.However,the photosynthetic heat tolerance of Magnoliaceae plants is still unclear.Methods In this study,we used chlorophyll fluorescence method to exam the photosynthetic heat tolerance of 23 species of Magnolicaeae plants in a common garden.In order to analyze the relationships of photosynthetic heat tolerance with leaf morphology and temperature niche,for each species,we measured leaf morphological traits and calculated the temperature niche across their geographic distribution areas.Important findings The temperature that causes 50％decrease of the maximum photochemical quantum efficiency of photosystem Ⅱ(T50)ranged from 46.1 to 56.7 ℃,with significantly higher T50 of evergreen species than that of deciduous species.For leaf morphology,T50 was positively correlated with the leaf area but was not significantly correlated with the leaf thickness.For temperature niches,T50 was positively correlated with mean annual air temperature and minimum air temperature of the coldest month but was not significantly correlated with maximum air temperature of the warmest month.A weak phylogenetic signal was found in T50,indicating that T50 was influenced by leaf morphology and environment conditions,rather than phylogeny.Our results suggested that photosynthetic heat tolerance of Magnoliaceae species were generally strong,but its adaptation may not be driven by high temperature environment.Future extreme high temperature events may severely threaten deciduous Magnoliaceae plants living in the warmer areas.
维普
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