Abstract:

Aluminum(Al) toxicity is a major limiting factor for yield and quality in crop production in acid soil. Micromolar concentrations of Al³⁺ may inhibit root elongation and consequently influence water and nutrient uptake, resulting in poor plant growth. The microanalysis of the elements was conducted on Zhechun 3 by using Transmission Electron Microscope (TEM) and Energy Dispersive X-ray (EDS) to examine the distribution of Al³⁺ in root tips and Al resistance of soybean. We found that Al³⁺ stresses resulted in irregularly thickened cell wall, increased number of mitochondria, expanded nuclear membrane, and densified precipitates of vacuole. Under the highest Al³⁺ concentration, the mitochondria and other organelles disappeared but cell wall. We detected Al in cell wall, mitochondria and electron-dense precipitates of vacuole of root tip cell under the 10 mg L^-1Al³⁺ stresses by EDS. With the increase of external Al³⁺ concentration treated, the weight and atomic percentage of Al in the organelles increased. The Al³⁺ was found in nuclei when the external Al³⁺ was over 60 mg L^-1. And there was no Al³⁺ in mitochondrion under 60 mg L^-1 and 90 mg L^-1Al³⁺ treatments and electron-dense precipitates of vacuole under the 90 mg L^-1 Al³⁺ stresses. The 14 days Al³⁺ stresses significantly inhibited the growth of root system. The content of Al³⁺ in cell wall was most significantly impacted by the external Al³⁺ concentration. The atomic number of P / Al in cell wall and mitochondria decreased with increased Al³⁺ content. EDS can be used to determine the subcellular location of Al³⁺. As the treatment concentrations of Al³⁺ increased, Al³⁺ primarily accumulated in the cell wall, gradually gathered in part of the organelles and nuclei. The Al³⁺ concentrations also decreased from out layer to insider in the cell.

Key words: Al³⁺ stresses, Soybean, Root tip cell, Transmission Electron Microscope-Energy Dispersive X-ray Analysis, Root growth