02787nam a2200505 a 450000100080000000500110000800800410001910000250006024500820008526000480016730000100021550000220022552015440024765000130179165000120180465000210181665000160183765000100185365000130186365000140187665000100189065000210190065000140192165000230193565000090195865000260196765000140199365000120200765000100201965000220202965000140205165300140206565300230207965300150210265300110211765300140212865300140214265300180215665300250217465300220219965300160222165300140223765300150225165300150226615570731997-09-10       1996    bl uuuu  m   00u1 u    #d1 aANDRADE, L. R. M. de  aPhysiological studies on varietal differences in aluminum tolerance in wheat.  a[Fukuoka, Japan]: [Kyushu University]c1996  a131p.  a[Tese Doutorado].  aDifferential Al-tolerance in plants, particularly wheat varieties has been extensively studied, but the mechanisms of Al toxicity and tolerance are still not well understood. The objective of this work was to investigate the mechanisms of Al-tolerance in wheat varieties screened for Al-tolerance by the hematoxylin staining method, with emphasis on a) the formation of a plant-induced pH barrier in the rhizosphere and b) the exudation of chelator ligands. A second objective was to clarify the effect of Al on the metabolism of malate in roots leading to its excretion using 14C tracer technique. Selected six wheat varieties differing in Al tolerance were used to determine the combined effects of Al and N sources on solution pH changes and nutrient absorption by plants. NO3- uptake was severely inhibited by the presence of Al while NH4+ uptake was little affected. Al decreased the amounts of Ca, Mg, and K accumulated in whole plants independent of N sources. The changes in the solution pH were a consequence of general effect of Al on nutrient uptake, msinly N (NH4+ and N03-), and they were not directly correlated with the scoring of Al-tolerance. Plants grown in N03--N accumulated more Al in the roots and it might be related to solution pH-changes. Tolerant varieties accumulated less Al. It was concluded the differential Al-tolerance among those varieties could not be explained solely by the ability of plants to maintain a high solution pH in mixed N solutions. The root apex (root cap, meristem, and root elongation ...  aaluminum  amalates  aplant physiology  arhizosphere  aroots  atoxicity  avarieties  awheat  aÁcido Orgânico  aAlumínio  aFisiologia Vegetal  aRaiz  aRelação Solo-Planta  aRizosfera  aToxidez  aTrigo  aTriticum Aestivum  aVariedade  aAluminium  aDiferenca varietal  aDifference  aMalato  aMecanismo  aMechanism  aOrganic acids  aPlant soil relations  aSoil deficiencies  aSoil toxity  aTolerance  aTolerancia  aToxicidade