Effects of planting depth and flooding period on germination and emergence of swallow wort (Cynanchum acutum)

Effect of 13 planting depths and 6 flooding periods on germination and emergence of swallow wort were investigated under greenhouse conditions. Results showed that swallow wort seeds emerged from up to 6 cm depth. The highest emergence occurred in the first, second, third and fourth week after emergence from 0.5 cm; 0.5, 1 and 1.5 cm; 1.5 cm; and 1.5 cm planting depth, respectively. At the end of the fourth week, 6.5 cm depth treatment had zero emergence. Increasing burial depth resulted in induced secondary dormancy. Increasing flooding period, did not affect germination percentage. However, fresh weight, radicle and hypocotyle lengths under flooding conditions were decreased significantly compared to control. Seeds flooded for 3 and 21 days had the highest and lowest fresh weight, respectively. Hypocotyle length was highest under zero and one day flooding treatments, but lowest under 14 days flooding treatment. Radicle length was highest under 0, 1, 3 and 7 days flooding treatments and lowest under 14 and 21 days flooding treatments.