Differential response to potassium permanganate of regenerable and of non-regenerable tissue cell walls from maize callus cultures

Abstract

Type I maize ( Zea mays L.) callus typically consists of two kinds of tissue, one type is capable while the other is incapble of regenerating whole plants. Exposing Type I callus to a 20 mM potassium permanganate (KMnO 4) solution (pH 7.2) resulted in a brown precipitate forming on intact non-regenerable tissues in the callus. Residue from homogenized callus also reacted with KMnO 4. The precipitate could only be dissolved in acid and permanganate could be re-formed from the dissolved precipitate using the strong oxidants potassium periodate (KIO 4) or sodium bismuthate. These data suggest that the brown precipitate is manganese dioxide (MnO 2). Callus exposed to a 20-mM KMnO 4 solution of pH 3.0, produced less MnO 2. This callus when exposed to Feulgen reagent developed a red-violet color only on non-regenerable tissue. A similar Feulgen reaction occurred with callus treated first for 2 min with a 34.8-mM acidic solution of KIO 4. Even regenerable tissue reacted with Feulgen reagent with prolonged exposure to KIO 4. The Feulgen results indicate that a highly oxidizable carbohydrate is associated with non-regenerable tissue but not regenerable tissue and it is the oxidation of this material by KMnO 4 that generates MnO 2. Residue from homogenized callus still reacted with KMnO 4 when washed three times with acetone, 1 N HCl, dimethyl sulfoxide, saturated (0.5 M) EDTA, or when heated in a boiling water bath for 20 min. However, washing the residue with 1 N KOH caused a 6-fold reduction in the formation of MnO 2. The results from these residue-washing experiments indicate that the highly oxidizable carbohydrate associated with non-regenerable tissue may be a hemicellulose. Manganese dioxide, formed from KMnO 4 by pH adjustment, also was found to bind to homogenized-callus residue. The reaction of non-regenerable tissue with KMnO 4 has proven to be a useful method for assessing the quantity of non-regenerable tissue in maize callus and may be useful as a marker for developmental changes in maize cells.