The influence of temperature and water potential on the germination of seven different dry‐stored seed lots of Stellaria media

Summary Experiments were made on seven dry‐stored seed lots of Steliaria media (L.) Vill to assess the effect of water potential and temperature on germination. These seed lots were from different sources and their age ranged from freshly harvested to 5 years in dry storage. Germination was recorded at regular intervals at five constant temperatures (5‐25°C) in all combinations with eight water potential regimes (from 0 to ‐1.4 MPa). The results showed that seed lot had a significant effect on the percentage, rate and spread of germination Differences in germination behaviour in the seed lots appeared to be related to the durations of dry storage. Freshly harvested seed exhibited signs of dormancy, with the lowest percentage and longest mean germination time. Seed lots that had been in dry storage for more than 1 year took increasingly longer to germinate, particularly under less favourable conditions. In contrast, germination percentages were highest in the 3‐year‐old seed. The constant temperature and water potential achieving maximum germination was independent of seed lot as was the water potential achieving the highest germination rates. However, the temperature achieving the highest germination rate was dependent on seed lot. The spread in germination time was largest for the freshly harvested and oldest seed samples. Rates of germination against temperature over the range of water potentials studied were complex.