Seed Dormancy and After-Ripening Response Among Wild and Cultivated Lesquerella (Physaria fendleri and P. gordonii).

Seed dormancy has been proposed as a general bet-hedging strategy for wild plant populations enabling them to persist during unfavorable environmental conditions. Germinations that spread through time are often advantageous in the wild to ensure a number of plants will reach reproductive maturity amidst abiotic and biotic constraints, if any. Wild populations of Physaria usually contain plants that significantly vary in size and total biomass due to this differential germination.  To further understand seed dormancy in wild populations as well as after-ripening response in Physaria, we sampled 13 populations of P. fendleri (syn. Lesquerella fendleri) and P. gordonii (syn. L. gordonii) from various localities in Arizona, New Mexico, and Texas. We subjected the collected seeds to different after-ripening regimes, storing them over two saturated salt solutions (LiCl and MgCl₂) to equilibrate seed moisture levels, at three storage temperatures (5, 25, and 35^oC) for various lengths of time (4, 8, 12 weeks) and then germinating them at two temperatures (constant 24^oC and alternating 15/25^oC). Results indicate significant differences on final percent germination between the different plant sizes in the wild, among storage durations, and between temperatures of germination. We further reviewed each site’s climatic data and other associated population parameters to try and find association with the observed germination responses in addition to comparing these responses to that of a cultivated P. fendleri.