Al toxicity in soybean roots

Aluminum is one of the major causes for soil degradation, in particular in acidic soils, where soil minerals release soluble Al that limits the growth of plants. Unfortunately, acidic soils comprise ca. 40% of the world’s arable land and are typically present in the areas that are more favorable for intensive agriculture. Our LEXRF show that the AL accumulation is rather rapid process and Al remains concentrated in cell walls with exposure time.


P. Kopittke et al., Plant Physiology (2015)




The results obtained in this study have revealed that toxic effects of aluminum are already exerted within the first 5-30 min of exposure in specific cells located in a region approximately 5-10 mm behind the root tip. Since traditional techniques are not sensitive to access accumulation of aluminum in these initial stages we used a combination of synchrotron-based low-energy X-ray fluorescence spectromicroscopy (LEXRF) at the TwinMic beamline (Elettra Sincrotrone Trieste) and high-resolution secondary ion mass spectroscopy (NanoSIMS) to examine the spatial distribution of Al on a cellular and subcellular level. This integrated approach allowed us to identify the sequence of processes whereby Al reduces the growth of roots in rather short term. The obtained results demonstrate that the majority of Al starts to accumulate within the walls of cells in the outer root tissues (as shown in Figure 1) and this preferential storage in the walls of the outer tissues continues even after exposures of 24 h (Figure 2). This observation is particularly important since the cells located in the region 5-10 mm behind the root tip are the ones responsible for the root growth via walls loosening.
Our findings clearly show that the accumulation of Al is rather rapid process and Al remains concentrated in the cell walls with exposure time. The binding of Al to the cell walls exerts toxic effects, leading to inhibition of cell elongation and growth. The results clearly indicate that for overcoming the deleterious effects of Al it is important to focus on traits related to cell wall composition as well as traits involved in wall loosening. 
 

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Identification of the primary lesion of toxic aluminum (Al) in plant roots
Peter M. Kopittke, Katie L. Moore, Enzo Lombi, Alessandra Gianoncelli, Brett J. Ferguson, F. Pax C. Blamey, Neal W. Menzies, Timothy M. Nicholson, Brigid A. McKenna, Peng Wang, Peter M. Gresshoff, George Kourousias, Richard I. Webb, Kathryn Green, Alina Tollenaere , Plant Physiology  (2015)

doi: 10.1104/pp.114.253229.
Last Updated on Tuesday, 22 December 2015 15:24