AL uptake by black spruce seedlings: Persistence of organic acids in al treated rooting cultures

Abstract

Experiments were conducted to monitor the pH and the persistence of simple organic acids (oxalic, citric, malic, glycolic acid) with and without Al complexation in rooting cultures (sand, peat, solution-only) under non-sterile conditions, and to characterize pertinent short-term responses of black spruce seedlings (Picea mariana [Mill.]) to subsequent changes in the rooting solutions. It was shown that the organic acids decayed within about five days unless the cultures were treated with a decay-controlling fungicide such as Captan, an antoxidant containing N-(trichloromethylthio)-4-cyclohexene-12-dicarboximide. Aluminum complexation did not increase the persistence of the organic acids except for oxalic acid. In all cases, the decay of the organic acids (or of the equivalent carboxylates) led to a simultaneous increase of solution pH which was most pronounced in the non-buffered solution cultures without Al. Captan did not affect the growth of black spruce seedlings, but was lethal to yellow birch (Betula alleghaniensis Britton) seedlings. The pH of tissuemized roots taken from the black spruce seedlings following treatments with oxalate and citrate (within and without Al) reflected the change of pH within the culture solutions.