germination tests

Tony Gurnoe, San Diego Botanic Garden

Baccharis vanessae, Encinitas baccharis, was originally described from a small population in Encinitas, California, just a couple of miles from the San Diego Botanic Garden (SDBG). The last individual to live within the garden was documented in 1997 and has not been observed since. The nearby type locality has also dwindled to just over two dozen individuals. Last year the team from the SDBG joined the efforts to conserve Encinitas baccharis by monitoring this population and collecting seeds from the few maternal lines available. Most of these seeds went into seed banks as part of the California Biodiversity Initiative and California Plant Rescue programs, but a cohort were also grown in SDBG’s nursery. This fall Baccharis vanessae will be reintroduced to the botanical garden with the goal of gaining a better understanding of how the species behaves in varying soil types and exposure scenarios. Meanwhile, SDBG staff continue to work with other populations, other institutions, and various other agencies toward the culmination of major in situ reinforcement and establishment of long-term management plans for Baccharis vanessae.

Contributing Author(s): 
Date Recorded: 
Friday, October 9, 2020

Alex Seglias, Denver Botanic Gardens

Plant biodiversity is being lost at an accelerated rate. To conserve native plants, many institutions are turning towards ex situ conservation methods, such as storage in seed banks. However, not all seeds are able to survive in seed bank conditions or they may be short-lived. Alpine species in Italy and Australia have been shown to lose viability at a quicker rate in seed banks compared to low-elevation species. To understand if alpine species from the Rocky Mountains of Colorado exhibit this same pattern, I used accelerated ageing experiments to simulate storage in a seed bank and expedite loss of viability. Ten samples of 50 seeds for four species (Castilleja puberula, Heterotheca pumila, Physaria alpina, and Saussurea weberi) were rehydrated in a dark incubator at 20°C and 47% humidity for two weeks. Following rehydration, the seeds were placed in a drying oven at 45°C and 60% humidity to age the seeds at various intervals of time. Following the ageing process, the seeds were placed into previously determined germination conditions (stratification followed by incubation at 20/10°C for one month). All species had P50 (time to 50% germination) values of <13.7 days, which is the threshold to consider a species short-lived in seed banks. These results suggest that we can’t haphazardly store seeds and assume that all species will survive for decades in seed banks. Rather, we need to assess what environmental and evolutionary conditions might preclude a species from being long-lived in storage and determine measures to mitigate loss of viability over time.

Contributing Author(s): 
Date Recorded: 
Friday, October 9, 2020

Alexandra Seglias (Denver Botanic Gardens)

Nicola Ripley (Betty Ford Alpine Gardens)

Brittany Roberts Marshall (Betty Ford Alpine Gardens)

 

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Alpine ecosystems are particularly vulnerable to climate change. The Denver Botanic Gardens are seeking to protect rare species from these regions, banking seeds from multiple Alpine populations by maternal line. However, collecting seed from these remote areas comes with multiple challenges. Seed production is dependent on the previous year's winter weather, there is a short window for flowering and seed setting, the phenology changes rapidly, and many sites are difficult to reach.
After gathering seed, researchers at Denver Botanic Gardens perform germination trials and grow seedlings to be reintroduced. Plants are also added to the living collections at Denver Botanic Garden and the Betty Ford Alpine Botanic Gardens to further preserve these rare species.

Contributing Author(s): 
Date Recorded: 
Thursday, May 21, 2020

Shawn C. McCourt, Sally M. Chambers, and Bruce K. Holst, Marie Selby Botanical Gardens

The genus Harrisia (Cactaceae) comprises 20 narrowly endemic species of night-blooming cacti with two widely separated geographic ranges, including South America south of Amazonia, as well as the West Indies and southern Florida. Commonly known as aboriginal prickly-apple, H. aboriginum is a sprawling, multi–stemmed, columnar cactus endemic to ancient native American shell mounds, as well as coastal berms, coastal grasslands, and maritime hammocks in four counties along the southwest coast of Florida. This federally-listed species is in steep decline, primarily due to the development of beachfront property, invasive species dominance, and the erosion of coastal barrier islands. Some populations have disappeared entirely. Researchers at MSBG have been conducting an inventory of extant populations, assessing the health of each population, and determining what genetic variation (if any) occurs across the species’ geographic range. When possible, a small portion of seed has been collected for seed banking and to grow plants for the augmentation of shrinking populations and introduction to ecologically suitable sites situated above projected rises in sea level. To date, we have visited nine sites and collected detailed demographic data for 89 plants. Spines were collected from all 89 plants for DNA extraction and the testing and developing of microsatellite loci. Seeds from seven fruits were collected from three sites. Data presented represent the preliminary findings of our work, which has a focus on the importance of maintaining genetic diversity in ex situ collections for the purpose of rare plant conservation.

Contributing Author(s): 
Date Recorded: 
Wednesday, March 4, 2020