Allelopathy in Heracleum laciniatum: Inhibition of Lettuce Seed Germination and Root Growth

Abstract

AbstractBoth dark and red light germination of lettuce seeds (cv. “Maikönig”) as well as their root and hypocotol elongation were inhibited when the seeds were sown in petri dishes together with a few seeds of Heracleum laciniatum Horn. This inhibition was not significantly counteracted by the presence of gibberellic acid (GA3) or/and 6‐benzylaminopurine (BA). However, a large proportion of the lettuce seeds germinated abnormally (only cotyledons emerged) when treated with BA in the presence of Heracleum seeds. GA3 had alone no significant effect on abnormal germination, but it counteracted the effect of BA to some extent.The inhibitory effect of Heracleum seeds gradually disappeared during a moist incubation period of one to seven days in darkness at 25°C.When lettuce seeds were pre‐incubated together with Heracleum seeds for one to five days the remaining, non‐germinated lettuce seeds had lost their ability for subsequent germination in darkness in distilled water. This induced dark dormancy was to a great extent broken by red light, but not by GA3 or/and BA.H. laciniatum seeds inhibited the germination of Salix pentandra seeds and to some extent also the germination of radish but had no effect on the germination of spruce.