Effect of high temperatures on imbibition, germination, and thermal death of velvetleaf (Abutilon theophrasti) seeds

Abstract

Seeds of velvetleaf (Abutilon theophrasti Medic.) were treated for various durations at temperatures from 40 to 60 °C. Rate of water uptake increased with temperature of imbibition. Germination of imbibed (soft) seeds was not affected by 40 °C imbibition for 30 h. At temperatures ≥ 43 °C, an inverse relationship was seen between temperature and time of imbibition required to reduce germination by a given level. Seeds exposed to temperatures up to 55 °C in dry or humid air or imbibed in osmotica of polyethylene glycol 6000 showed inhibitory effects on germination increased as time of exposure and seed water content increased. Seeds with low water content required longer exposures or higher temperatures to reduce germination. Heat treatments of <2 h caused greater germination reduction when applied after 24 h of imbibition than at the beginning. A heat stress of 1 h at 52 °C at the beginning and repeated after 24 h imbibition produced greater germination inhibition of soft seeds than a single 2 h 52 °C treatment at the beginning.