Germination response of Russian wildrye to variations in seed mass at fluctuating temperatures.

Abstract

The effects of seed mass and fluctuating temperatures on the germination and heterotrophic seedling development of 3 seed sources of Russian wildrye, Psathyrostachys juncea (Fisch) Nevski, were studied. Seeds that weighed 2.4, 3.0, 3.6, and 4.2 +/- 0.1 mg of each seed source were germinated in an unlighted incubation chamber at 5-10 degrees C, 5-15 degrees C, 10-l5 degrees C, and 10-20 degrees C. Germination and heterotrophic seedlings development were assessed using: 1) mean time to germinate (T/1), 2) the mean proportion of seeds to germinate (G) and 3) mean maximum radicle and coleoptile extension. Data were analyzed using a 4 X 4 X 3 factorial analysis of variance (n = 144) comprised of main effects, temperature (T), seed mass (M), and seed source (S). Time to germination was significantly affected by T (F = 647.44, P < 0.0001), S (F = 28.29, P < 0.0001) and the T X S (F = 4.71, P < 0.0003) and S X M (F = 2.21, P < 0.0489) interact. The mean maximum proportion of seeds to germinate was significantly affected by T (F = 13.63, P < 0.0001), S (F = 10.53, P < 0.0001), M (F = 8.11, P < 0.0001) and the T X M interaction (F = 2.21, P < 0.0276). Radicle extension was significantly affected by T (F = 21.94, P < 0.0001), S (F = 14.29, P < 0.0001), M (F = 12.70, P < 0.0001), and the T X S (F = 13.69, P < 0.0001) interaction. Coleoptile extension was significantly affected by T (F = 810.24, P < 0.0001), S (F = 68.83, P < 0.0001), M (F = 56.00, P < 0.0001), and the T X M (F = 3.84, P < 0.0003) interaction. Apparently, Syn-A seeds germinate more vigorously and have longer coleoptiles than Vinall but apparent differences remain confounded between seed sources since the effects of seed age and maternal environment cannot be eliminated from the study.