| As the global climate changes,human agricultural economic life is also becoming frequent,changes in the global environment makes the material cycle,water cycle are constantly accelerating,terrestrial ecosystems,marine ecosystems and other natural ecosystems are suffering from serious damage,Ecological balance has long been broken.Under the influence of extreme weather,the drought stress of plants is becoming more and more serious,and the land area of salinization is increasing with the improper development and utilization of land.The Yellow River Delta has a different degree of salinity distribution under the long term geological conditions due to the impact of the Bohai Sea water for a long time.The reed community,as a typical salt-tolerant plant community in the delta area,under the influence of salt stress,Characteristics of the physical and chemical characteristics will be changed in response to salt stress,such as plant under the influence of salt caused by reduced leaf area,decreased number of grains and so on.Studies have shown that reed plants under salt conditions,plant stem will produce Na+ starch granules to inhibit the salt damage to the leaves.This study investigated the interactive responses of P.australis seedlings to different hydrologic and salinity conditions with a focus on plant growth,leaf morphology,biomass and allocation,gas exchange and chlorophyll fluorescence physiology.P.australis is regarded as an important global species that has the potential to enhance the structure,function and stability of the Yellow River Delta.Results from a 56-day experiment,revealed that both salt and water intensity greatly reduced seedling growth,and altered leaf morphological traits,and photosynthetic characteristics.In contrast the frequency of flooding influenced leaf length,total chlorophyll,intercellular carbon dioxide and the limiting value of stomata,the pattern of biomass partitioning was not affected by the experimental treatments.The interaction of water intensity,frequency and salt addition decreased the transpiration rate and stomatal conductance and promoted water use efficiency.P.australis may adapt to an environment with low precipitation,and sufficient water supply may enhance the ability of P.australis to survive in soil with higher salinity.In this study,P.australis exhibited a strong potential to adapt to salt and water stress,whereas seedlings under the well-watered conditions could relieve osmotic stress and ion toxicity.Salt and water intensity,as two independent factors,can affect every area of P.australis growth significantly.As to water frequency,leaf characters and photosynthetic characteristics were influenced by the factors.Precipitation frequency(below period of 6 days)minimally influenced its growth.The timing and magnitude of precipitation pulses are important triggers that influence plant growth and particularly reflect the physiological response under conditions of increased moisture after a rainfall.Salt and water intensity interactions affected biomass and photosynthetic characteristics notably.Under interactions of salt and water frequency,partly photosynthetic characteristics were changed significantly,similarly with the effect of interactions of all three factors.Prolonging the period of precipitation may have greater effects on the plant.Therefore further experiments are needed to confirm this viewpoint.Infrequent precipitation has been suggested to be a significant factor affecting the structure and function of arid land ecosystems.P.australis will play an important role in ecological restoration and local natural ecosystems around the Yellow River Delta as extreme weather occurs with greater frequency as a result of climate change.Studying the effects of salt,water intensity and frequency on multiple plant functions on plants can help glean useful information for coastal habitats especially wetland protection and management in regions such as the Yellow River Delta. |
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