Lignosulfonates: Novel promoting additives for plant tissue cultures

Lignosulfonates (LIGNs) are low-cost by-products from the paper industry and are already commercialized as fertilizers. Because earlier laboratory and glasshouse assays had shown a beneficial effect of LIGNs on rooting and general plant vigor, their incorporation in several plant tissue culture types was examined here. The present assays indicated that well-chosen concentrations of LIGNs, whether they were chelated with Ca or Fe, stimulated growth of a normal and an habituated sugarbeet callus, improved multiplication rate and vigor of a shoot-proliferating poplar cluster, and increased the rooting percentage of holly, ginseng, and poplar shoots. Complementing the exogenous rooting auxin with LIGNs enhanced the increases of endogenous levels of indoleacetic acid and its aspartate conjugate in the basal parts of poplar shoots at the rooting inductive phase. Although LIGNs exerted some effects in the absence of the growth regulators, they could not replace them. Their possible mode of action is discussed