EFFECTS OF CHILLING, LIGHT AND NITROGEN-CONTAINING COMPOUNDS ON GERMINATION, RATE OF GERMINATION ARID SEED IMBIBITION OF CLEMATIS-VITALBA L

Effects of chilling (5 degrees C) period, light and applied nitrogen ( N) on germination (%), rate of germination (d to 50% of total gerinina tion; T-50%) and seed imbibition were examined in Clematis vitalba L. In the absence of chilling, light and N, germination was minimal (3 %) . When applied alone, both chilling and N increased germination. Chill ing for 12 weeks increased germination to 64%, and 2.5 mM NO3- or NH4 increased germination to 10-12%. Light did not increase germination w hen applied alone, but did when applied in combination with chilling a nd/or N; Half the seed germinated when light was combined with 2.5 mM NO3- or NH4+. The influence of chilling, light and/or N on germination was greater when Combined, than when either factor was applied alone; Both oxidized (NO,) and reduced (NH4+) forms of N increased germinati on, but non-N-containing compounds did ndt, Suggesting the response wa s due to N and not ionic or osmotic effects. Without additional N, T-5 0% decreased from 16-20 d at zero chilling, to around 5 d at 8 and 12 weeks chilling. Although T-50% was not influenced by an increase in NO 3- or NH4+ from 0.5 to 5.0 mM, it did increase with additional applied N thereafter. However, the magnitude of the N effect was small compar ed to that of chilling. Like germination, seed imbibition increased wi th a longer chilling period, but in contrast imbibition decreased slig htly with increased applied NO3- or NH4+. It is argued that increased imbibition is not directly related to an increase in total germination , but that it may be related to the rate of germination. Possible mech anisms involved in the reduction in dormancy of C. vitalba seed are di scussed. (C) 1997 Annals of Botany Company.