A comparism of plasma membrane response to Al~(3 ) stress between polygonaceae plants(Fagopyrum esculentum Moench,Fagopyrum dibotrys(D.Don) Hara,Polygonum cuspidatum Sieb.Et Zucc.,Polygonum pubescens Bl.) and gramineae plants(Oryza sativa L.,Triticum aestivum L.) was studied under controlled conditions with quartz sand culture.The results summarized as follows: Proline content,MDA content and membrane permeability in six plant species enhanced with increased Al~(3 ) concentration.Al~(3 ) triggered the evolution of proline in gramineae plants much higher than in polygonaceae plants,MDA content and membrane permeability were at a higher rate in Fagopyrum esculentum Moench and Fagopyrum dibotrys(D.Don) Hara than in the other four plant species.During the same period,the SOD and POD activity in leaf both increased in Fagopyrum esculentum Moench and Triticum aestivum L.,while decreased both in Polygonum cuspidatum Sieb.Et Zucc.and Oryza sativa L.SOD and POD activity in Fagopyrum dibotrys (D.Don) Hara and Polygonum pubescens Bl.raised with an increased of Al~(3 ) firstly(25 mg/L Al~(3 )),and then declined despite Al~(3 ) stressed concentration(100 mg/L Al~(3 )) still intensified.It was concluded that the change of membrane permeability in polygonaceae plants was a kind of cell damaged mechanism caused by oxidative stress with Al~(3 ),while in gramineae plants was a kind of defensive mechanism.