Effects of range, seasons and storage under different temperatures on germination of Senecio vulgaris (Asteraceae) seeds

Invasive plants colonize new environments, become pests and cause biodiversity loss, economic loss and health damage. Senecio vulgaris (Common groundsel, Asteraceae), a cosmopolitan weed wildly distributes in the temperate area, is reported with large populations in the north–eastern and south–western parts, but not in southern, central, northern or north-western part of China. We studied the germination behavior of S. vulgaris to explain the distribution and the biological invasion of this species in China. We used seeds originated from 12 populations in native and invasive range (six populations in each range) to conduct germination experiments in a climate chamber and ambient condition. When incubated in climate chamber (15°C) seeds from the majority of population showed >90% germination percentage (GP) and the GP was equal for both ranges. The mean germination time (MGT) was significant different among the populations. Under ambient conditions, significant effect of range, storage conditions (stored at 4 or 27°C) and seasons (in summer or autumn) were observed on the GP while the MGT was only affected by the season. In autumn, the GP was higher (38.6%) and the MGT was slightly longer than that in summer (4.5%). In autumn, seeds stored at 4°C showed higher GP than those stored at 27°C, and seeds from invasive population revealed higher GP than those from native populations. High GP and short time for seed emergence demonstrated that in S. vulgaris seeds checked in this study were from Senecio vulgaris ssp vulgaris, the non – dormancy subspecies. The results also implied that the high temperature exceeds the threshold for S. vulgaris to germinate and storage at high temperature cause S. vulgaris seeds lost the viability greatly. This demonstrates the reason why in Wuhan S.vulgaris can’t establish natural and viable populations, and also explain why S.vulgaris is scattered in China.