Germination responses of Juncus acutus (Juncaceae) and Schoenus nigricans (Cyperaceae) to light and temperature

Seed germination of Schoenus nigricans and Juncus acutus was compared at two photoperiods (12:12 h light:dark photoperiod and 24 h dark environment) and seven temperature regimes (10, 15, 20, 25, 30, 15:25 and 20:30 °C). Final germination of S. nigricans was affected by interaction between temperature and photoperiod and germination speed was only affected by temperature. Germination was arrested at 10 and 15 °C. The seeds of this species showed dormancy and did not exceed 37% of germination in any condition tested. The final germination and germination speed of J. acutus were affected by light, temperature and their interaction. Although this species was able to germinate at 10 °C (30%), high temperatures from 20 to 30 °C and alternating temperatures of 15:25 and 20:30 °C yielded germination percentages higher than 90%. Total darkness delayed germination in relation to the 12 h photoperiod. Both J. acutus and S. nigricans seeds did not germinate at 30 °C in darkness, but they did at the same temperature with 12 h photoperiod. Our results show the high final germination of J. acutus, as well as possible seed dormancy phenomena in S. nigricans.