EFFECT OF SEED SIZE AND ECOLOGICAL FACTORS ON GERMINATION OF Emex spinosa

The effect of ecological factors on germination of Emex spinosa was examined in laboratory experiments. Seeds were graded manually into large, medium and small, having weights 3.333, 1.952 and 0.886 g /100 seeds, respectively. Seeds germinated over a range of 10-20°C, with optimum germination (89.17%) at 15°C, showing a trend towards decrease in germination percentage, germination index and markedly increasing mean germination time with lowering temperature. Seed germination was observed under both light and complete darkness. Emex spinosa germination was 77.5% with distilled water and 41.66% at 150 mM NaCl concentration, while mean germination time increased and germination index decreased by increasing the salinity levels. Germination of E. spinosa decreased from 68.33% to 0.83% as osmotic potential increased from 0 to -0.8 M Pa. Mean germination time and germination index also decreased by increasing water stress. Emex spinosa seedling emergence was at its highest (50.83) at soil surface, and no seedling emerged at a depth of 8 cm, while mean germination time and germination index decreased by increasing seeding depth. Seed size showed non-significant results on all germination traits. Our results indicate that E. spinosa have ability to germinate under various conditions but the percentage that germinates will be different under different ecological conditions.