Effects of After-Ripening and Germination Regimes On Seed Germination Behavior of Seven Species of Physaria Germplasm.

The after-ripening response has been well documented in many plant species but studies are lacking in new oilseed crops such as Physaria. In a factorial experiment, we tested the effect of different after-ripening periods and germination conditions on freshly harvested seeds of seven Physaria species, P. fendleri, P. gracilis, P. rectipes, P. argyraea, P. thamnophila, P. sessilis, and P. recurvata.  The seeds were stored for 4 and 12 weeks over two saturated salt solutions (LiCl and MgCl₂) to equilibrate seed moisture at three storage temperatures (5, 25, and 35^oC). We likewise tested the dormancy-breaking protocol on these species using the conditions for P. fendleri previously recommended for use in genebanks. The germinations were conducted with light (1,052 lux) and gibberellic acid (GA₃) (100 ppm) and without them. Results suggested that the conditions previously set for P. fendleri are also adequate for P. gracilis, P. sessilis, and P. recurvata, but may still be not optimal for the perennial species, P. argyraea, P. thamnophila, and P. rectipes.  Overall higher germinations were obtained with light and GA₃ treatments.  In all species, we observed slight differences between total germinations after 4 weeks and 12 weeks of storage with higher values evident only in P. thamnophila, P. recurvata, and P. fendleri after the fresh seeds were subjected to the longer after-ripening period at warm temperatures.