germination test

Cheryl Birker, Rancho Santa Ana Botanic Garden

The California Seed Bank at Rancho Santa Ana Botanic Garden has a germination testing program to monitor the viability of its many conservation seed collections. Germination tests are conducted on all incoming seed collections before they are placed in freezer storage, and for all rare seed collections, follow-up germination tests are conducted periodically in order to monitor their viability throughout the storage term. Germination testing also allows for experimentation with different pretreatments for breaking seed dormancy to inform propagation protocols. Germination tests are conducted on agar and maintained in a temperature controlled germination chamber. Seeds must be treated with a bleach and Tween¨ solution to reduce microbial growth prior to sowing on agar, and this treatment must sometimes be repeated before the test is completed. Germination tests can run anywhere from two weeks to eight months, with weekly monitoring for new germinations and microbial growth. Seedlings are produced as a byproduct of germination testing, which can be transplanted from agar to soil and grown in a nursery for inclusion in a living collection or for second generation seed collecting as an extra means of ex-situ conservation.

Contributing Author(s): 
Date Recorded: 
Thursday, May 2, 2019

Ashley Clayton and Peter Zale, Longwood Gardens

At the Valmont Bog in Hazelton, PA, there are populations of three, state-listed taxa of Platanthera: P. ciliaris, P. blephariglottis, and P. xbicolor, a natural hybrid of the other two species. They are threatened by forest succession, climate change, silt-laden runoff, and herbicide spraying. However, as is the case for most native orchids, conservation efforts are hindered by limited propagation information. To support in situ and ex situ conservation of these species, this experiment was designed to determine the most effective mycorrhizal fungi for in vitro germination of each taxon. In August 2018, pelotons were isolated from the roots of each species and maintained in culture. Multiple capsules from each orchid species were then collected the following month. Seeds were surface sterilized in a 10% bleach solution for 18 minutes and rinsed with distilled water. They were plated on an agar-based medium containing powdered Liriodendron tulipifera wood and inoculated with one of the three fungal isolates. Visual inspection showed that at least 71% of seeds on each plate contained healthy embryos except for seeds originating from one capsule of P. xbicolor, which only about a third had embryos. Visual observation also revealed an association between the hyphae and the rhizoids of protocorms. The peak germination occurred between four and five weeks after sowing. After seven weeks, seed germination ranged from 0 to 27%. Compared to a previous preliminary experiment, the addition of mycorrhizae decreased the time of peak germination from several months to about one month. The effect of each mycorrhiza on germination percentage and protocorm development is still being determined.

Contributing Author(s): 
Date Recorded: 
Friday, May 3, 2019

Philip Gonsiska,Bok Tower Gardens

Ziziphus celata is an endangered shrub endemic to Polk and Highlands Counties in central Florida. Germination in this species has generally been very low, and previous observations have suggested that upwards of 75% of seeds set by Z. celata may not be viable. In January 2019, cutting tests were conducted to estimate the viability of Z. celata seeds harvested in summer 2018. Dissected seeds were categorized as “normal”, empty, moldy, “spongy”, and those having shrunken embryos. Those in the “normal” category were thought to be viable. Of the 103 seeds dissected, 36 (34.95%) appeared “normal”, 35 (33.98%) were empty, 24 (23.3%) were moldy, six (5.83%) had shrunken embryos, and two (1.94%) were “spongy”. In earlier work, soaking seeds in a 0.1% liquid smoke solution resulted in a germination rate of 26.7%, which thus far is the highest germination rate in our data set from any experimental seed treatment applied to Z. celata. Therefore, seeds from 2018 were soaked in either a 0.1% liquid smoke solution or reverse osmosis water for 24 or 48 hours. They were then sown in 72-cell trays along with unsoaked control seeds. These trays will be monitored for germination for six months, and the realized germination rate will be compared to the hypothetical percentage of viable seeds from the cutting tests. Preliminary results of this experiment will be presented.

Contributing Author(s): 
Date Recorded: 
Thursday, May 2, 2019

CPC 2019 National Meeting Videos now in PI Portal! See Cheryl's Germination Testing Video

Apologies for cross posting (this is why we need an announcements channel :)), but the CPC National Meeting Videos are ready for viewing in the PI Portal. They will be moved to plant nucleus in our next phase of development (coming soon!). Take a sneak peak at Cheryl's

Recommendations for incorporating phylogeny into a survival analysis of germination data?

According to the attached review of germination data analysis (McNair et al. 2012), time to event analysis (survival analysis) is the recommended approach for analyzing germination data. Does anyone know of a study that incorporates phylogeny as a covariate in a survival analysis?

Setting up germination tests

I'm new to germination testing and will be running germination trials on lots of different species (mostly midwest natives). What kind of plates/containers do you use? What kind of media- agar, blotter paper, sand?) do you use and what do I need to know about keeping it watered/sterilized/labeled? 

Do you always steralize your seeds before "planting" them? If so, what protocol do you follow?

Please share your trials and tribulations! Thanks!

What kind of germination/growth chamber do folks recommend for seed viability testing?

Our growth chamber broke recently and we're hoping to replace it with something cost-affordable, reliable and not too big for our relatively small space. It will sit in a room shared with seed processing equipment (and people), a biomass oven and is used with some frequency.

Does your institution have germination data of seeds stored after 1, 5 or 10 years?

CPC is interested in learning about general longevity of rare species after several years in storage.  If enough data exists, then we will be able to do a meta-analysis.