Az Eszterházy Károly Tanárképző Főiskola Tudományos Közleményei. 2004. Sectio Biologiae. (Acta Academiae Paedagogicae Agriensis : Nova series ; Tom. 25)

Zsoldos, F., Vashegyi, Á., Pécsváradi, A. and Bóna, L.: Aluminium toxicity in roots: correlation between root elongation and potassium fluxes in aluminium-sensitive and aluminium-tolerant cereal species

160 Zsoldos, F. et al. with pH>5 mostly forms insoluble oxides and alumino-silicates. At lower pHs there is a release of bioactive forms of Al, particularly Al

3" and ,,A1

1

3", which is toxic to plants (Marschner 1995). In this text, we denote Al as Al without implying a specific Al species. Aluminium toxicity is primarily expressed by drastic inhibition of root growth in Al-sensitive genotypes (Taylor 1988; Bona et al. 1998). Typically, the main axis of the roots is inhibited, and the root become stubby, thickened, brown, brittle and occasionally necrotic (Archambault et al. 1997; Hecht-Buchholz and Foy 1981). The toxic effect of Al on plants are well documented, however, the physiological reasons for inhibition of root elongation by Al is not completely understood so far. Differential sensitivity of species and genotypes has been extensively studied and several mechanisms of Al tolerance have been suggested including chelation of Al via formation of Al complexes with organic acids, acidic polypeptides and/or proteins (Kochian 1995; Kochian and Jones 1997; Libaga et al. 2004; Lipton et al. 1987; Ma et al. 2001; Miyasaka et al. 1991; Ogawa and Matsumoto 2001). Al-phosphate complexes may also occur on the surface of the roots, furthermore, within cell wall or on the surface of the plasma lemma influencing the Al toxicity of plants (Clarkson 1967; Lüttge and Clarkson 1992; McCormick and Borden 1973; Miyasaka et al. 1991, Naidoo et al. 1978; Wagatsuma et al. 1983). The objective of our study was to determine the effects of Al stress on the growth and potassium transport of roots of different cereal species with varying phosphate (P)-supplies hoping that our results could be valuable tools for studying the physiological basis of mechanisms of Al tolerance in plants. Materials and Methods Plant Materials Common wheat (Triticum aestivum L. cv. Jubilejnaja 50), durum wheat (T

. durum Desf. cv. GK Betadur), triticale (xTriticosecale Wittmack cv. GK Marco) and rye (Secale cereale L. cv. GK Wibro) provided the experimental material in this study. Earlier tests in acid soil and culture solutions showed that GK Wibro is an Al-tolerant, Jubilejnaja 50 and GK Marco are moderately tolerant type and GK Betadur is a moderately sensitive to Al toxicity (Bona et al. 1992, 1995; Vashegyi et al. 2002). Seeds were washed and germinated in Petri dishes in darkness at 25°C, then seedlings were placed on stainless screens over glass beakers. Each beaker contained 300 ml growth solution and 8 seedlings. Seedlings were