Aluminum-tolerant Protoplasts from Roots Can be Collected with Positively Charged Silica Microbeads: a Method Based on Differences in Surface Negativity

A new technique was developed for the collection of Al-tolerantplant cells. The procedure takes advantage of the differencein surface charge between Al-tolerant and Al-sensitive protoplasts.Equal volumes of freshly prepared, positively charged silicamicrobeads (0.05% w/v) and purified protoplasts derived fromroot tips (2x10⁵ ml^-1) of rice, maize or pea were mixed andthen centrifuged on a discontinuous Ficoll gradient. Intactprotoplasts from the Al-tolerant plant were recovered mostlyin the bottom fraction, those from the Al-sensitive plant wererecoverd at the uppermost interface, and those from the plantwith intermediate tolerance to Al were collected at the middleinterface. Moreover, the pattern of fractionation was unrelatedto the diameter of the protoplasts. The technique should beuseful in future investigations of the physiological and biochemicalproperties of Al-tolerant cells or their plasma membranes. (Received April 19, 1995; Accepted September 1, 1995)