Weed seed germination after short–term light exposure: germination rate, photon fluence response and interaction with nitrate

Abstract

SummaryThree laboratory experiments were carried out to answer certain important questions related to the use of‘photo control’as a weed–control strategy. The first experiment documented that seeds of Rumex obtusifolius L. and Silene noctiflora L. germinated more slowly in total darkness than after a short exposure to light, whereas there were no significant differences for Cerastium fontanum Baumg. This suggests that seedling emergence in total darkness would not only result in fewer seedlings, but would also be slower; hence the crop might be given a competitive advantage. The second experiment demonstrated that germination of C. fontanum and S. noctiflora showed a linear response to the logarithm of photon fluence. with levels >1 μmOl m‐2 being stimulatory. This suggests that a near–complete elimination of light during dark harrowing would give the best result. R. obtusifolius, however, had a sigmoid dose–response curve with a lower threshold for germination at 500 μmOl m‐2. Hence, this species had a clear threshold under which unnecessary germination was prevented. The third experiment tested for interaction between light and nitrate in their stimulatory effect on germination percentages. For Descurainia sophia (L.) Webb ex Prantl, R. obtusifolius and Thlaspi arvense L., but not for C. fontanum. such interactions were significant. This stresses the fact that light response will vary substantially depending on the seed's environment.