Germination Characteristics of Three Species ofCruciferae

Abstract

Germination of tumble mustard (Sisymbrium altissimumL.), tansy mustard (Descurainia pinnata(Walt.) Britton), and yellowflower pepperweed (Lepidium perfoliatumL.) is partially dependent on total degree hours of incubation (temperature above 0 C times the duration of incubation). This relation was similar under constant or alternating temperatures. Alternating temperature regimes with −20 C inhibited germination, and greatly depressed subsequent germination at optimum temperatures. Tansy mustard and yellowflower pepperweed have temperature-dependent after-ripening requirements. Germination of all three species responded similarly to osmotic stress. The relation between tumble mustard germination under osmotic or soil moisture stress is dependent on the texture of the soil substrate. A mucilaginous coating greatly aids the germination of yellowflower pepperweed seeds on the surface of media under low (0.05 to 0.2 bars) moisture tension. Germination of seeds of the three species recovered in soil samples from the field is radically different from that of freshly harvested material. The seeds acquire a dormancy which is broken irregularly under ideal conditions for germination.