The Response Of Mulberry(Morus Alba L.) To Water Stress On The Red Soil Containing Weathered Mudstone

Under natural conditions,the vertical distribution of soil can be characterized by the existence of a mixed medium layer of soil and weathered material during the transition from surface soil to bedrock.The existence of weathered mudstone under the topsoil in the soil profile is a common phenomenon in nature.When drought occurs,plants can penetrate the soil with a small thickness to absorb the water in the lower layer of weathered material.The presence of weathered mudstone directly affects the migration process of soil moisture.The effect of weathered soil on plant water use strategy is helpful to judge whether the supply of soil water can meet the long-term survival of plants.Therefore,it is necessary to study the water consumption mechanism of plants in weathered soils,which is good for the growth of local plants and the sustainable utilization of water resources.In this study,mulberries were conducted as the research object,one of the typical native plant in southern China,and the mulberry experienced continuous water stress under different weathering contents.The effect of water stress on plant growth and changes in photosynthetic physiological parameters were monitored in the experiment period.Pot experiments were designed to reflect the law of photosynthetic physiological indicators to changes in soil water content,and the soil water utilization of mulberries under weathering content.The main conclusions of this study were showed as follows:（1）Weathered mudstone had significant effects on saturated water content and field water capacity of red soil.With the increase of weathered mudstone,the effective pores of soil increased first and then decreased.The weathered mudstone improved the hydraulic conductivity of red soil,and the saturated hydraulic conductivity of weathered soil were higher than those of red soil.（2）Under water stress condition,there was no significant difference between the aboveground biomass and the underground biomass of mulberries in the weathered content of 10%,30%,50%and 70%,and no significant difference between the aboveground biomass of mulberries in red soil and pure weathered.But the underground biomass of mulberries in red soil was significantly higher than that of pure weathered material.The underground biomass of red soil was significantly higher than that of mulberries with weathered mudstone.The root to shoot ratio of mulberries showed a significant upward and then downward trend with the increase of the weathering content,and the root volume decreased first and then increased with the increase of the weathering content.The root surface area,total root length and average root diameter of mulberries under 70%weathering content were significantly higher than those with 10%weathering content.（3）The relationship between plant net photosynthetic rate,stomatal conductance,transpiration rate,and soil moisture can be divided into three stages:it rose briefly with the decrease of soil moisture,then decreased rapidly,and then decreased slowly with the decrease of soil moisture.The intercellular CO₂ concentration of mulberries first decreased and then increased as water was reduced,and the water use efficiency increased and then decreased.（4）The soil water availability thresholds of red soil containing weathered（0%,10%,30%,50%,70%,100%）were 39.2%,51.7%,53.3%,45.5%,38.6%and 34.6%of the field moisture capacity respectively,and the most suitable threshold of soil water availability for mulberries were 79.4%～84.4%、72.2%～87.1%、83.7%～87.6%、87.4%～89.1%、80.2%～83.3%、81.0%～85.4%of the field moisture capacity respectively.There was no significant difference in the utilization of high-productive and high-efficiency water of mulberries almong various soils with different contents of weathered mudstone,and weathered materials affected“the productive”and“efficiency”level of mulberries on soil water.