Imbibition temperature affects on seedling vigor: In crops and shrubs

Imbibition at cold temperatures reduces seedling vigor of some species, but is beneficial to others, We used 3 rangeland shrubs and 8 agronomic crop s pecies to test for a general relationship between imbibition temperature (5 to 30 degrees C) and seedling vigor measured as post-germination growth; a nd to test for an effect of imbibition temperature on seed water uptake and dry weight loss during imbibition. Imbibition temperatures between 5 and 1 5 degrees C were correlated with greater seedling length of the shrubs whil e most crops were favored by imbibition temperatures between 20 and 30 degr ees C, Winter wheat (Triticum aestivum L.) response to inhibition temperatu re was similar to that of the shrubs. Generally, shrubs had lower post-germ ination growth than crops, and during imbibition most crop seeds lost less weight than shrub seeds. Winter wheat had high weight loss as well as high seedling vigor. Seed water content generally increased with increasing imbi bition temperature; however, winter wheat, kochia (Kochia prostrata (L.) Sc hrad.), and big sagebrush (Artemisia tridentata Nutt.) had significantly le ss water when imbibed at 30 degrees C than when imbibed at lower temperatur es. The differences due to temperature suggest the relationship between inh ibition temperature and seedling vigor is a general phenomenon related to t he physiology of water uptake and to seed respiration (as indicated by weig ht loss). Therefore, we recommend that optimum imbibition temperatures be d efined by species and incorporated into seed-testing guidelines. This appea rs particularly important for species that do not have a long history of cu ltivation and whose response to temperature may differ significantly from t hat of crops.