SEED MASS AND DETERIORATION: IMPLICATIONS FOR EX SITU LONGEVITY
Genna, N.G.1 and Perez, H.E.1
1Environmental Horticulture Department, University of Florida, Gainesville, Florida, USA
Contact: Nicholas Genna, email@example.com
Seed bank storage is financially challenging and hinges upon the successful maintenance of seed viability in a variety of species over many decades. Accessions must be monitored for viability in a timely manner and replaced or regenerated if significant deterioration is detected. To date, evidence suggests that seed storage behavior is not uniform and longevity varies across species and accessions. Seed mass is a plant functional trait that has often been examined as a potential source of longevity differences. Currently, evidence suggests that interspecific seed mass variation does not influence the rate of seed deterioration. However, little is known about how intraspecific seed mass variation drives deterioration ex situ. Here, we assessed mass-based deterioration responses in two Rudbeckia mollis (Asteraceae) seed lots differening in age. The first seed lot was stored for one year at room temperature (23–24°C, 30–40% RH) while the second seed lot consisted of relatively fresh seeds stored at 4oC for four months. Air density separation of each seed lot generated light, intermediate, and heavy mass-based classes. All mass classes were subjected to germination testing under alternating simulated seasonal temperatures including winter (22/11oC), spring (27/15oC), fall (29/19oC), and summer (33/24oC). Mass-based germination responses were similar across temperatures and mass classes for the relatively fresh seed lot. Conversely, mass-based germination responses diverged in the one year old seed lot with light seed germination percent being 2.8 times higher than heavy seeds under summer temperatures. Saturated salt accelerated aging (SSAA) was subsequently utilized to promote deterioration in the relatively fresh seed lot to understand if a mass-based germination response would develop. We found that seed mass significantly influenced germination following increasing aging stress. Final germination percent in light class seeds was 1.7 times greater than intermediate or heavy seeds after 20 d of SSAA. Similar germination responses between one year old seeds and relatively fresh seeds subjected to SSAA suggest that mass dependent viability loss may occur in R. mollis. Future research will investigate underlying mechanisms that may promote differential deterioration in seeds of different mass of this species.