Changes in Photosynthetic Characteristics of Zea mays L.and Broussonetia Papyrifera(Linn.)L'Hér.ex Ven.under Progressive Soil Drought
Under the influence of climate and karst topography,some karst areas are still experiencing increasingly severe and frequent drought conditions,seriously impacting the photosynthetic and chlorophyll fluorescence properties of plants.In this study,two soils(silty loam(Ld)and silty clay loam(Lc))and two plant species(Zea mays L.and Broussonetia papyrifera(Linn.)L'Hér.ex Ven.))in the karst area were taken to study the changes in photosynthetic parameters and chlorophyll fluorescence variables in brachy-cardia and maize leaves under progressive drought conditions.The results showed that during drought stress,the net photosynthetic rate(A),transpiration rate(E)and stomatal conductivity(gsw)of both plants decreased gradually,the intercellular CO2 concentration(Ci)increased significantly during the late stage,and the water use efficiency(WUE)first increased and then decreased.The WUE of Zea mays L.was higher than that of Broussonetia papyrifera(Linn.)L'Hér.ex Ven.in the same soil,and the maximum WUE of the same plant species in different soils was higher in Ld than in Lc.The initial fluorescence(Fo)of Zea mays L.under both soil condi-tions decreased firstly during the early stage,stabilizing during the middle stage,and then increased rapidly during the late stage.The maximum photochemical efficiency(Fv/Fm)showed an opposite trend to that of Fo.In comparison,Fo of Broussonetia papyrifera(Linn.)L'Hér.ex Ven.only decreased during the early stage and then increased,and its Fv/Fm trend was also opposite to that of Fo.According to the trend of leaf A,gsw and Ci,stomatal restriction and non-stomatal restrictions were identified as the main factors af-fecting the photosynthetic characteristics of Zea mays L.and Broussonetia papyrifera(Linn.)L'Hér.ex Ven.in the pre-middle and late drought period,respectively.Moreover,the alternating time nodes of the two types of restriction in Lc and Ld were day 10 and day 9 for Zea mays L.and day 10 and day 7 for Broussonetia papyrifera(Linn.)L'Hér.ex Ven.When these time points were exceeded,the plants could not recover from photosynthesis even after rehydration,this node can be referred as the point of deficit regulation irriga-tion.This study can deliver a scientific fundament for understanding the adaptability and water use characteristics of plants to arid envi-ronment and field water management in karst areas.
karstsoilZea mays L.Broussonetia papyrifera(Linn.)L'Hér.ex Ven.photosynthetic parameterschlorophyll fluo-rescence parametersstress of drought
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