Stomatal Phenotype And Behavior Of Picea Species And Ecological Divergence In This Genus

Global climate change mainly manifests as frequent extreme events such as regional temperature rise and drought,which will significantly affect the mountain ecosystem.Stomata,the portal of gas exchange between plants and the external environment,which is sensitive to environmental changes and determines the important physiological processes such as photosynthesis,respiration and transpiration of plants.Therefore,stomatal phenotype and their behavior to respond to environmental changes determine the survival and distribution of plants,and then cooperate with other functional traits to drive plant evolution and speciation.Species in the genus Picea?spruce?are usually compose coniferous forests or mixed broadleaf-conifer forest in the middle high and low latitudes in the northern hemisphere alpine.In China,they are mostly distributed in western alpine and subalpine areas,which are extremely sensitive to global change and weak in ecosystem resistance.So it is of great value to study the adaptability of spruce.In the distribution range of spruce,the annual average temperature and precipitation have significant difference.The stomatal distribution of different species is different obviously and their phylogenetic relationships are clear.Thus,this is not only providing an ideal material to study the regulation of stomatal phenotype and behavior for us,but also providing a basis to discuss the correlation of phylogenetic history and stomata and other functional traits.Therefore,we measured stomatal anatomy and photosynthetic characteristics by common garden and control experiment to systematic analyze the phenotypic plasticity of stomatal traits and photosynthetic characteristics of spruce species.And then the intrinsic relation of stomatal phenotype and their regulation of stomatal behavior under light and drought treatment were analyzed.Finally,based on their phylogenetic relationship and distributional environment,a spatial evolutionary and ecological vicariance analysis?SEEVA?was used to quantify and test the divergence between sister lineages and analyze the environmental and functional traits selection effect.The main results were as follows:?1?The mean phenotypic plasticity index?PPI?of photosynthetic traits was higher than that of stomatal traits of two species from arid habitats and two species from wet habitats planted in two common gardens?wet and dry areas?.The stomatal length?SL?and width?SW?of adaxial surface,the transpiration rate?Tr?and specific leaf weight?LMA?were sensitive to drought.There was no definite correlation between plasticity and the environment of species origin,because only Picea crassifolia that from arid habitat and P.asperata that from wet habitat showed habitat adaptation.P.crassifolia adapted to drought by increasing its instantaneous water use efficiency?iWUE,PPI=0.52?and maintaining a constant net photosynthetic respiration ratio?P/R,PPI=0.10?,while the other three species all showed reduced physiological activities under drought.?2?All stomatal anatomical characteristics and gas exchange characteristics of six endemic species of Chinese spruce were significantly different,except the operating stomatal conductance?G_s?and the minimum stomatal conductance(G_min).Stomatal density?SD?was negatively correlated with SL but not related to the SW and S_area.SW and SL were negatively correlated with the stomatal response rate of light and drought,respectively.However,stomatal characteristics did not significantly affect the maximum stomatal conductance,but the stomatal density was negatively correlated with the minimum stomatal conductance(G_min and G_d-min).?3?In the process of spruce speciation,the temperature variables were separated at the base node and the precipitation variables were separated at the terminal node.The conservative traits were LMA and Pn?QVI=0.42,0.44?,which reflected the selective reservation of ancestors in cold environment.Meanwhile,linear stomatal density?LSD?,carbon stable isotope ratio(?¹³C‰)and water potential of 50%loss of water conductivity(P₅₀)were relatively convergent?QVI=0.93,1,0.80?,which were unrelated to current habitats while only P₅₀ positively correlated with precipitation variables.In conclusion,this study found that the stomatal phenotypic plasticity of Picea species was low,plasticity of stomatal traits of regulation was high,and P.crassifolia had strong adaptability of all.SD was negatively correlated with SL,SL and SW could affect stomatal regulation ability of behavior,and SD was closely related to leaf respiration intensity.In the process of Picea evolution,the ancestral groups first experienced the separation of temperature selection,and then experienced the separation of precipitation selection,where LMA and Pn were the selective reservation of Picea to adapt to the environment.These results above not only revealed the adaptability,stomatal phenotypic plasticity and relationships between stomatal phenotype and behavior of spruce,but also provided a new approach to elucidate the relationship between ecological separation,functional traits and speciation,and provide certain reference for spruce forest conservation and tree species selection of artificial afforestation.