Germination responses to temperature and dormancy breaking treatments in Nitraria tangutorum Bobr. and Nitraria sibirica Pall.

Abstract

Five independent experiments were designed to determine the optimum temperatures and methods for improved germination in Nitraria tangutorum and Nitaria sibirica. The optimum germination temperature for N. tangutorum was 25/35 degrees C, and for N. sibirica, 25 degrees C, 30 degrees C and 20/30 degrees C. Soaking in water for 48-120 h improved germination rate (GR) for N. tangutorum, and soaking for 24 h promoted GR and germination percentage (GP) for N. sibirica. In soaking experiments, the highest GP was observed for treatments of 48 h in 0.1% GA(3) solution and the 120 h soak in 0.02-0.1% GA(3) solutions for N. tangutorum. Highest GP values for N. sibirica were obtained following soaks of 48-120 h in water, 48-120 h in 0.2% KNO(3) solutions, 24 h in 0.1% GA(3), and 48-120 h in 0.02-0.1% GA(3) solutions. Optimal germination for N. tangutorum was obtained by the combination of 120 h soaking in 0.05-0.1% GA(3) solution and 25/35 degrees C incubation, which resulted in 80-83% germination at 14 d. Prechilling and preheating promoted germination of N. tangutorum, while preheating stressed seed of N. sibirica. The substrate moistened with KNO(3) or GA(3) solutions promoted germination of both species. Scarification with concentrated H(2)SO(4) for 3-6 h promoted germination of N. tangutorum, but damaged many of the embryos. After the mechanical scarification, all seeds died. Seeds of the tested species possess non-deep physiological dormancy.