Germination and seedling growth on substrates with extreme pH-laboratory evaluation of buffers.
Germination and early seedling growth of Pinus contorta and Picea glauca were examined in distilled water (pH 6.3) (control), eight acidic buffer solutions (pH 2.2), and eight alkaline buffer solutions (pH 9.0). Four of the acidic buffers increased germination of P. contorta, compared with the control. All but one alkaline buffer reduced germination of P. contorta. All but two of the sixteen buffers reduced germination of P. glauca and five buffers totally inhibited germination. Seedling growth of P. contorta at pH 2.2 varied between 10 and 43% of the control, and at pH 9.0 varied between 0 and 59% of the control. The equivalent seedling growth for P. glauca was 0-23% and 0-28%, respectively. Citric acid-potassium hydrogen phosphate was the most stable and physiologically innocuous acidic buffer; glycine-sodium hydroxide was the most innocuous alkaline buffer. The osmotic potential of citrate-phosphate buffers was varied, using polyethylene glycol. The results indicated that the osmotic potential of the buffers was not low enough to explain reductions in germination and seedling growth, the components of the buffer were apparently toxic. The results are applicable to the revegetation of mine spoils and tailings affected by extreme acidity or alkalinity.