Quantification of Aluminum-Induced Changes in Wheat Root Architecture by X-ray Microcomputed Tomography

ABSTRACT Root architectural traits are of fundamental importance for plant performance, especially under unfavorable soil conditions. This study examined the effect of aluminum (Al) toxicity in different growing media (nutrient solutions and soil) on root architecture of two wheat (Triticum aestivum L.) cultivars with different Al tolerances. Seedlings were grown in acidic and limed soil and in two contrasting nutrient solutions. Root systems of soil-grown plants were scanned using x-ray microcomputed tomography (µCT) while that of nutrient solution–grown plants were assesses using WinRhizo, 3 and 5 days after planting (DAP), respectively. Aluminum caused significant reduction of all examined root traits (number of seminal roots, root length, length of the longest seminal root, root surface area, and root volume). Growth in acidic soil caused significant reduction in root length, length of the longest seminal root, and root surface area at 5 DAP. Soil-grown plants produced a larger root system compared to plants grown in nutrient solutions. Aluminum toxicity–induced differences of root traits were also found between different nutrient solutions. Beside the well-known reduction of root length, Al toxicity had a profound effect on other root architectural traits. X-ray µCT has revealed root architectural changes under specific conditions of acidic, Al-toxic soil. Differences obtained in Al-induced effects on root architecture between different nutrient solutions as well as between different growing systems emphasize the need for further study of root architecture, especially under specific conditions of Al toxicity in acidic soils.

[1]  C. Poschenrieder,et al.  Fast root growth responses, root exudates, and internal detoxification as clues to the mechanisms of aluminium toxicity and resistance: a review , 2002 .

[2]  R. Littell.  SAS System for Mixed Models , 1996 .

[3]  L. Kochian.  Cellular Mechanisms of Aluminum Toxicity and Resistance in Plants , 1995 .

[4]  L. Kochian,et al.  Aluminum Toxicity in Roots : Correlation among Ionic Currents, Ion Fluxes, and Root Elongation in Aluminum-Sensitive and Aluminum-Tolerant Wheat Cultivars. , 1992, Plant physiology.

[5]  S. Mooney,et al.  Quantifying the effect of soil compaction on three varieties of wheat (Triticum aestivum L.) using X-ray Micro Computed Tomography (CT) , 2011, Plant and Soil.

[6]  M. Mccully,et al.  ROOTS IN SOIL: Unearthing the Complexities of Roots and Their Rhizospheres. , 1999, Annual review of plant physiology and plant molecular biology.

[7]  Jon E. Shaff,et al.  GEOCHEM-EZ: a chemical speciation program with greater power and flexibility , 2009, Plant and Soil.

[8]  D. Samac,et al.  Plant improvement for tolerance to aluminum in acid soils – a review , 2003, Plant Cell, Tissue and Organ Culture.

[9]  C. Bustamante,et al.  High-throughput two-dimensional root system phenotyping platform facilitates genetic analysis of root growth and development. , 2012, Plant, cell & environment.

[10]  Z. Rengel,et al.  Evaluation of Triticum aestivum germplasm from Croatia and Yugoslavia for aluminium tolerance , 2004, Euphytica.

[11]  L. Kochian,et al.  Development of a Novel Aluminum Tolerance Phenotyping Platform Used for Comparisons of Cereal Aluminum Tolerance and Investigations into Rice Aluminum Tolerance Mechanisms1[C][W][OA] , 2010, Plant Physiology.

[12]  S. Mooney,et al.  Developing X-ray Computed Tomography to non-invasively image 3-D root systems architecture in soil , 2011, Plant and Soil.

[13]  Saoirse R Tracy,et al.  The X-factor: visualizing undisturbed root architecture in soils using X-ray computed tomography. , 2010, Journal of experimental botany.

[14]  Z. Rengel,et al.  Genotypic differences in wheat Al tolerance , 2004, Euphytica.

[15]  R. Chaney,et al.  The Physiology of Metal Toxicity in Plants , 1978 .

[16]  R. Shen,et al.  Aluminum targets elongating cells by reducing cell wall extensibility in wheat roots. , 2004, Plant & cell physiology.

[17]  T. Rufty,et al.  Altered aluminum inhibition of soybean root elongation in the presence of magnesium , 2001, Plant and Soil.

[18]  L. Herrera-Estrella,et al.  The role of nutrient availability in regulating root architecture. , 2003, Current opinion in plant biology.

[19]  E. Delhaize,et al.  Aluminum Tolerance in Wheat (Triticum aestivum L.) (II. Aluminum-Stimulated Excretion of Malic Acid from Root Apices) , 1993, Plant physiology.

[20]  E. Mutert,et al.  Global extent, development and economic impact of acid soils , 1995, Plant and Soil.

[21]  E. Delhaize,et al.  Aluminum Toxicity and Tolerance in Plants , 1995, Plant physiology.

[22]  E. Delhaize,et al.  Aluminum Tolerance in Wheat (Triticum aestivum L.) (I. Uptake and Distribution of Aluminum in Root Apices) , 1993, Plant physiology.

[23]  J. Lynch.  Root Architecture and Plant Productivity , 1995, Plant physiology.

[24]  P. Testillano,et al.  Morphological and Cellular Changes in Rice Roots (Oryza Sativa L.) Caused by Al Stress , 2012 .

[25]  J. Anderson,et al.  Linkage of RFLP Markers to an Aluminum Tolerance Gene in Wheat , 1996 .

[26]  T. Carter,et al.  Genotypic Rankings for Aluminum Tolerance of Soybean Roots Grown in Hydroponics and Sand Culture , 2001 .

[27]  Peter J. Gregory,et al.  New approaches to studying chemical and physical changes in the rhizosphere: an overview , 1999, Plant and Soil.

[28]  D. Parker,et al.  Organic acid secretion as a mechanism of aluminium resistance: a model incorporating the root cortex, epidermis, and the external unstirred layer. , 2005, Journal of experimental botany.

[29]  Guo-ping Zhang,et al.  Aluminium tolerance in barley (Hordeum vulgare L.): Physiological mechanisms, genetics and screening methods , 2006, Journal of Zhejiang University SCIENCE B.

[30]  I. Mistrík,et al.  Rapid and simple method for Al-toxicity analysis in emerging barley roots during germination , 2006, Biologia Plantarum.