Submitted to: Canadian Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2015
Publication Date: 5/13/2016
Citation: Foley, M.E. 2016. Germination of leafy spurge (Euphorbia esula L.) seeds under alternating temperatures: the effects of amplitude, midpoint, and imbibition in gibberellic acid. Canadian Journal of Plant Science. 96:321-328.
Interpretive Summary: Leafy spurge is a noxious perennial weed of the Northern Great Plains. It reproduces and spreads both from seeds and buds on the crown and root system. Previously, we determined that germinating dormant leafy spurge seeds in water or gibberellic acid under a diurnal alternating temperature of 20:30°C (16 h:8 h) enhanced germination relative to constant temperatures. This temperature regime had an amplitude or difference in temperature of 10°C with a midpoint or average temperature of 23°C over the 24 h period. In this research, we examined the effect of other diurnal temperature regimes with various amplitudes and midpoint temperatures on germination in water and gibberellic acid. On average, diurnal temperature regimes that had a 10 or 15°C amplitude and 23°C midpoint displayed optimum germination in water and gibberellic acid.
Technical Abstract: Germinability of dormant leafy spurge seeds or the capacity to germinate under particular conditions is enhanced by a diurnal alternating temperature regime relative to a constant temperature. The aim of this research was to investigate alternating temperature amplitude and midpoint regimes for germination in water and gibberellic acid (GA3). The optimal regimes for germination in both water and GA3 were 20:30°C (16 h:8 h) and 20:35°C (19 h:5 h), which provided amplitudes of 10°C and 15°C, respectively, with both conditions having a midpoint temperature of 23.3°C. However, midpoint temperature of 22°C to 27°C were equally effective for germination under the 20:30°C and 20:35°C alternating temperature regimes. Additional alternating temperature regimes with amplitudes of 15°C (15:30°C and 10:25°C), 20°C (10:30°C), and 25°C (10:35°C) generally displayed reduced germination in both water and GA3, which is likely attributable to the low initial alternating temperature (=15°C) component of the regime relative to the higher initial temperature of 20°C for the optimum regimes of 20:30°C and 20:35°C. Regardless of the alternating temperature regime, seeds germinated in GA3 generally displayed =80% germination.