Stimulation of seed germination by humic substances: on the nature of the phenomenon

The wheat seed germination and seedling growth, as well as the effect of humic substances on seed development, were compared using soils and sand as substrates. Russian Plain soils were found to considerably inhibit seed germination. Pre-sowing treatment with humic preparations resulted in a significant stimulation effect on seeds sowed into sod-podzolic soil, but not into sand. Considering a well-known phenomenon of soil allelelotoxicity, we have suggested that stimulation of seed development by humic substances is a result of seed protection by them against the allelotoxin inhibitory effect.