Seed Coat Impermeability and Germination of Showy Crotalaria (Crotalaria spectabilis) Seeds

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Abstract
Showy crotalaria (Crotalaria spectabilis Roth) seed dormancy was due to seed coat impermeability to water. The seed coats became impermeable during later stages of maturation on the plant. When incubated immediately after harvest, 9% of the mature, black seeds (11% water content) imbibed water and germinated. The remaining 91% had impermeable coats and did not germinate. After dry storage for 3 months at 23 C, 24% of the seeds imbibed water and germinated. Seeds of another seed lot, which contained seeds of different maturity stages, attained 47% imbibition and germination after storage for 1 yr. The dry, less mature green seeds had a higher percentage (51%) of permeable seeds than did the black seeds (31%) from the same lot. Several seed coat treatments induced imbibition of water and germination of previously impermeable seeds. Effective treatments included piercing of seed coats, scarification with sandpaper, soaking in 70 C water, and simply applying pressure on the strophiole area. Covering the pressed strophiole with petroleum jelly significantly blocked imbibition and indicated that water entered the seeds at only the pressed area. However, studies indicated natural loss of impermeability in showy crotalaria seeds may occur at other sites as well.