Document: MIC-3-37-19

Population variation in the germination of the facultative winter annual Thlaspi arvens.

HENDRICKSON, A.* and M.A.FARRIS

Hamline University, St. Paul, MN 55104 USA ¹

Abstract:
Thlaspi arvens (Brassicaceae) can have either a summer or winter annual life history. To determine the relative frequencies of these two life history morphs in natural populations, we examined variation in the germination patterns of freshly ripened seeds both within and among five southern Minnesota populations. Seeds were collected when the siliques were dry but partially intact, and all seeds were collected within a six day period. Two replicates of 50 seeds from each maternal plant were planted in flats within 24 hours of collection and placed in the greenhouse. Germination was scored for 5 weeks, the flats were stratified at 5 C for three months, and post-stratification germination was scored. Total germination (fresh + stratified) varied significantly both within and among populations; between 36% and 97% of the planted seeds germinated in each population. The percentage of total germination that occurred in fresh, unstratified seed ranged between 15% and 98% in the five populations (p<0.001). At the population level, there was a strong positive relationship between the total number of germinated seeds and the proportion of those seeds that germinated before stratification. Populations collected later in the season had lower overall germination, even though only mature siliques were collected and all populations were collected within a six-day period. While over 50% of the observed variation was among populations, there was significant variation within populations for both germination characteristics. These results suggest that the relative proportions of summer and winter annuals may differ among these populations, and that most populations will have at least some individuals of each life history morph.

Keywords: germination, Thlaspi arvens, winter annual

This abstract is being presented at: 1:30 PM in session:
Oral Session #33: Plant Demography.