Germination characteristics of polymer-coated canola (Brassica napus L.) seeds subjected to moisture stress at different temperatures

Polymer coatings have recently been developed to prevent germination and thereby reduce undesirable emergence of fall-seeded canola (Brassica napus L.) in western Canada. However, recent observations suggest that if seeds are not exposed to moist soil conditions in the fall, these polymer coats may prevent imbibition and subsequent germination during the following spring. Our objective was to determine the effects of moisture stress and polymer coat on canola seed germination characteristics in the laboratory. Polymer-coated and non-polymer-coated canola seeds were germinated in polyethylene glycol (PEG 8000) solutions with initial osmotic potentials ranging from 0 to -1.25 MPa at 5 and 15 degreesC. Polymer coat treatments caused higher median germination times and lower final germination percentages compared with film-coated and uncoated control seeds. Germination characteristics of polymer-coated seeds were negatively influenced by decreasing initial osmotic potential, particularly at 5 degreesC. Although not always significantly different from the uncoated control, film-coated control seeds behaved similarly to those coated with polymers. Among the three polymer coat treatments examined, one polymer coat treatment consistently exhibited higher germination compared with the other two. The results of this study help explain the occurrence of low spring seedling populations of fall-seeded, polymercoated canola following a dry fall, particularly under low spring soil temperatures.