No abstract

Seeds of weed species require light to terminate dormancy and give way to germination. It is documented that sensitivity to light in Polygonum aviculare seeds increases during dormancy release. However, it is not known whether this sensitivity is lost during dormancy induction. The aim of this study was to investigate and quantify the changes in dormancy level of P. aviculare seeds during secondary dormancy induction as measured by changes in sensitivity to light in relation to soil temperature. Polygonum aviculare seeds were stratified at 5ºC until obtaining a minimum dormancy level. The seeds were then induced into secondary dormancy by burying them in pots containing soil which were stored at 10, 15, 20 and 25ºC for different time-periods. Polygonum aviculare seeds were exhumed periodically, exposed to different light treatments (Pfr/ P total-pythochrome = 0.76, 0.03 and 7.6 × 10 −4) or darkness, and incubated at 15ºC to test germination. Our results showed that the high sensitivity to light acquired during dormancy release and decreased during dormancy induction at a rate that was temperature-dependent. These changes in sensitivity to light were quantified as a function of the accumulation of thermal-time over a base-temperature of 7.9ºC during dormancy induction and were coupled with previous thermal-time index established for the dormancy release process. Both thermal-time indices allowed us to develop a model for the prediction of cyclic changes in sensitivity to light in relation to the thermal environment experienced by the seeds during burial. This model constitutes a valuable tool for predicting weed emergence in the field and to design management practices accordingly.