Morphological And Physiological Changes Of Roots In Different Soils Of Cotton And Their Responses To Mineral Element Absorption

As an important economic crop,cotton is also an important strategic material for the national economy and people's livelihood.The growth and development of cotton plants is always limited by mineral elements.The root system is a bridge connecting the plant to the soil environment and is a direct organ for the absorption,transportation and storage of mineral elements.In order to reveal the relationship between root morphology and physiology on mineral elements,this study started from the morphological,physiological and tissue structures of roots,and studied the changes of root morphology and physiology under different soil depths and the response relationship with mineral elements.The regulation relationship of mineral elements on root morphology,physiological characteristics and tissue structure.The root structure and the absorption,transport and storage capacity of mineral elements were discussed.The research results can lay a theoretical foundation for the cotton roots to absorb the transport nutrients.The main research contents and results are as follows:1)As the soil depth increases,the root length,specific root area,specific root volume,and nitrogen content of the roots gradually increase,and the root density gradually decreases.Nitrogen was positively correlated with root length,specific root area and root volume in 0-20 cm soil,and negatively correlated with root density.In the soil of 30-50 cm,nitrogen has a positive correlation with specific root length,specific root volume,specific root area and root density.In the soils of 20-30 cm and 50-60 cm,there was a negative correlation between nitrogen and specific root length,specific root volume,specific root area and root density.From the analysis of different mineral elements,it is known that the nitrogen,magnesium and sulfur elements have a positive correlation with the root morphological parameters,and the effect of nitrogen on the root length is more significant.Phosphorus and potassium were positively correlated with root volume.Principal component analysis showed that nitrogen and potassium showed a positive correlation between root length,specific root area and root volume,and nitrogen showed a strong positive correlation with root area.Calcium,magnesium and sulfur have a negative correlation with root density,and sulfur has a more significant effect on root density.2)There was a positive correlation between nitrogen and protein content in the middle and upper layers(0-30 cm)and nitrate reductase.At the same time,as the soil depth increased,protein content and nitrate reductase activity increased,while glutamine increased.The activity of the synthetase is reduced.In the middle and lower layers(30-60 cm),the relationship between nitrogen and protein content,nitrate reductase and glutamine synthetase was not significant.From the analysis of different mineral element levels,nitrogen showed a positive correlation between protein content and nitrogen metabolism enzymes.Phosphorus,magnesium and sulfur have positive correlations with protein content and nitrate reductase.Principal component analysis showed that nitrogen had a positive correlation with nitrogen metabolism enzymes.Nitrogen had a more significant effect on nitrate reductase.Sulfur and magnesium showed a negative correlation with nitrogen metabolism enzymes.The role of sulfur and nitrate reductase The effect is more significant.3)From the analysis of different regions in the root section,it is known that nitrogen promotes the increase of the area of cortical areas and the number of ray cells,and enhances the radial transport and axial transport ability of roots.Phosphorus and potassium promote the increase of the area of the middle column and enhance the axial transport capacity of the roots.Calcium,magnesium and sulfur promoted the total cross-sectional area of the root system and the area of the cortical area,which enhanced the axial transport capacity of the root.In addition,calcium and sulfur increased the number of ray cells,thus enhancing the radial transport capacity of the roots.From the analysis of different tissue structures in the column region of the root system,nitrogen promoted the average diameter of the primary xylem,the number of primary xylem cells and the ray cell area,and enhanced the axial transport capacity and radial transport capacity of the root column.Phosphorus and potassium all increase the average diameter of the primary xylem and enhance the axial transport capacity of the root column.Calcium,magnesium and sulfur increase the number of primary xylem cells and the area of ray cells,thus indirectly increasing the axial transport capacity and radial transport capacity of the middle column.In addition,sulfur also increases the average diameter of the primary xylem and further enhances the root column.Axial transport capacity.From the analysis of different tissue structures in the root cortex,nitrogen and calcium promoted the number of secondary xylem cells and the number of wood parenchyma cells,which enhanced the axial transport capacity and storage capacity of the root zone.Phosphorus promotes the average diameter of wood parenchyma cells and enhances root storage capacity.The effect of potassium on the promotion of various tissue structures in the cortical area is not obvious.Both magnesium and sulfur promoted the average diameter of secondary xylem,the number of secondary xylem cells,and the number of wood parenchyma cells,which enhanced the axial transport and storage capacity of the root cortex.Principal component analysis showed that there was a strong positive correlation between the amount of calcium and the number of primary xylem cells,and a strong negative correlation with the area of the cortical area: the total area of the section,which in turn enhanced the ability of the root axis to transport.Nitrogen showed a strong negative correlation with the ray angle,and showed a strong positive correlation with the average diameter of the parenchyma cells in the cortical area,which in turn enhanced the ability of root storage and radial transport capacity.