germination test

Ed Guerrant, Rae Selling Berry Seed Bank

Penstemon peckii (G3-S3 Federal SOC) is an Oregon endemic with a relatively compact range in the semi-arid Ponderosa pine forest east of the Cascade Mountains. The vast majority of known populations (ca 93%) are almost entirely within the Sisters Ranger District of the Deschutes National Forest. A 1992 Species Conservation Strategy by Cindi O’Neil found that it is “Best adapted to open full sun habitats, low vegetative competition and natural fire.” The natural fire frequency was 7 to 15 years, but active fire suppression for many decades had diminished and degraded habitat. Number one in the “What we do not know” list is “How long does Peck’s penstemon seed remain viable in the soil seed bank?” To address that question, in 1992 we gathered seeds from multiple populations across the species’ range. We mixed seeds from 11 populations into a single, large bulk sample in order to compare their survivorship in the soil seed bank and in an ex situ seed bank. In addition to initial trials of fresh and dried and frozen seeds, samples have been removed from the field and ex situ seed bank after 6, 12, 18 months, and then at 4, 15 and now 25 years. The current round of germination trials of 25-year old seeds is still underway, but to date, approximately 26% of those stored in the soil and 51% in the freezer have germinated. The species clearly has the capacity to form a long-lived soil seed bank.

Contributing Author(s): 
Date Recorded: 
Friday, May 4, 2018

Peter Zale and Matt Taylor, Longwood Gardens

Several species of Spiranthes native to the Eastern U.S. are considered rare, threatened or endangered by federal and state agencies. Using the Pennsylvania endangered Spiranthes casei as a model species, experiments were designed to determine optimal conditions for in vitro seed germination and seedling development. Seeds were collected in November 2015 from 10 individual plants found in three subpopulations in Elk and McKean counties, Pennsylvania, and air-dried for six weeks. Seeds were surface sterilized for 10 or three minutes in a 10% bleach solution, then plated onto a commercially available terrestrial orchid seed germination media: P723, M551 or K400 (Phytotechnology Labs, Shawnee Mission, KS) with 5 replicate plates. Seed germination ranged from 24 to 60 % and occurred on all three media only with the 3-minute treatment. None of the seeds treated with bleach for 10-minutes germinated and visual inspection revealed badly damaged embryos. After shoot initiation, 150 seedlings were transferred to individual test tubes on one of two media (P723 or P658) and each was given one of the three 24-hour light/dark photoperiod treatments for 10 months: 24/0, 18/6, or 0/24. Seedling survival and growth occurred in all treatments, but seedlings on P723 with the 24/0 or 16/8 photoperiod treatments had a significantly greater fresh weight, leaf length, number of roots and root length than light treatments on P658 and dark treatments. Results indicate Spiranthes seeds can be damaged by extended chemical scarification times and the light is essential for optimal seedling growth.

Contributing Author(s): 
Date Recorded: 
Friday, May 4, 2018