Plasma membrane of younger and outer cells is the primary specific site for aluminium toxicity in roots

Abstract

Experiments were carried out to identify the primary site for aluminium (Al) toxicity in roots. A1 accumulated in large amounts in the younger and outer cells in roots of pea and was retarded when the ionic strength of the A1 solution was high. Cell destruction was extensive in the regions with high A1 accumulation. The accumulation of AI in, and potassium (K) leakage from, the root tip were in the order pea > maize > rice, the same order as their sensitivity to AI.The protoplasts from the root tip portion of pea incubated with AI showed a wrinkled and uneven surface. The protoplasts progressively shrank and eventually collapsed. Viability decreased in this process. In the control protoplasts of maize, ~3-glucan formation was uniform on the spherical surfaces, whereas it was spotty in the Al-treated protoplasts; the cell wall material of the latter contained partly 1, 3-~-glucan which is known to be synthesised by 1, 3-fl-glucan synthase embedded in the plasma membrane. These results suggest that the specific site for AI toxicity is the plasma membrane of younger and outer cells in roots and that AI tolerance depends largely on the integrity of the plasma membrane.

Alterações morfológicas e acúmulo de compostos fenólicos em plantas de sorgo sob estresse de alumínio

“…Resultados similares foram observados por WAGATSUMA et al (1995), em raízes de ervilha, por DELIMA e COPELAND (1994), em raízes de trigo, e por LENOBLE et al (1996), em raízes de abóbora. Em raízes tratadas com Al +3 ocorreu engrossamento dos ápices em ambas as cultivares (Figura 1B), sintoma também relatado por Delhaize e RYAN (1995) e por SASAKI et al (1996) em trigo.…”

“…nas raízes e menor exsudação de ácido málico para a solução por parte da cultivar sensível, a intensidade da reação com hematoxilina férrica nos ápices radiculares foi bastante similar entre ambas as cultivares ( Figuras 1C,D,E). Uma correlação direta entre a tolerância ao Al +3 e a coloração das raízes com hematoxilina férrica é relatada em diversos trabalhos da literatura (POLLE et al, 1978;Wagatsuma et al, 1995;DELHAIZE et al, 1993). Todavia, RYAN et al (1993) (LENOBLE et al, 1996).…”

The plasma membrane strength of the root-tip cells and root phenolic compounds are correiated with Al tolerance in several common woody plants

“…Compared with other Al screening techniques for Al tolerance, namely the use of stains like eriochrome cyanine R (Ma et al 1997), hematoxylin (Polle et al 1978;Wagatsuma et al 1995), FDA (Yokota and Ojima 1995), FDA-PI (Koyama et al 1995;Ishikawa and Wagatsuma 1998), and callose deposition (Wagatsuma et al 1995), measurement of root elongation is the most popular method in spite of its inherent complexity (Rengel 1996). The significantly positive correlation between short-term Al tolerance and long-term combined tolerance (r=0.769**) suggests that tolerance to combined stresses of high AI, low P, and low pH especially in woody plants can be estimated using the short-term root elongation screening method.…”

Aluminium Tolerance Assessment of 141 Maize Germplasms in a Solution Culture

“…Hematoxylin, a dye commonly used in cytogenetic studies, has also been employed as a quick, nondestructive way of assessing plant genotypes for Al tolerance [24,25,[40][41][42]. Berezovskii et al [24] recommended a qualitative scale to rate different genotypes for Al tolerance based on how completely their roots were stained.…”