Hard Seededness and Germination of Small White Flower Morningglory

Abstract

Small white flower morningglory (Ipomoea obscura (L.) Ker-Gawl) has hard seeds. Scarification in 97.7% sulphuric acid for 40 to 120 minutes allowed germination, and the 80 minute treatment produced the fastest germination rate (recorded as coefficient of velocity). For acid scarified seeds germination did not differ at pHs ranging from 2.2 to 8.5, but the coefficient of velocity was greatest at a pH of 7.0, while germination decreased as osmotic potential increased from -0.19 to -0.76 MPa, and no germination occurred at -0.79 MPa. Cold scarification at 4°C did not allow germination of non-scarified seeds and had no effect on the germination of scarified seeds, which germinated equally well (>90%) at constant temperatures between 15 and 35°C. Germination at alternating temperatures did not differ from that at constant temperatures. Seeds on the soil surface did not germinate, but >85% emergence was recorded at sowing depths of 1 and 2 cm. Seeds sown at 8 and 12 cm did not emerge. Reducing light intensity (from 100 to 25% of full sunlight) did not affect seedling emergence or plant dry weight 12 weeks after sowing, but did delay the time to flowering. As this climbing weed can smother pineapple fields, it is important that effective control is achieved at the seedling stage.