Imbibition Temperature Affects on Seedling Vigor: In Crops and Shrubs

Abstract

Imbibition at cold temperatures reduces seedling vigor of some species, but is beneficial to others. We used 3 rangeland shrubs and 8 agronomic crop species to test for a general relationship between imbibition temperature (5 to 30°C) and seedling vigor measured as post-germination growth; and to test for an effect of imbibition temperature on seed water uptake and dry weight loss during imbibition. Imbibition temperatures between 5 and 15°C were correlated with greater seedling length of the shrubs while most crops were favored by imbibition temperatures between 20 and 30°C. Winter wheat (Triticum aestivum L.) response to imbibition temperature was similar to that of the shrubs. Generally, shrubs had lower post-germination 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 imbibition temperature; however, winter wheat, kochia (Kochia prostrata (L.) Schrad.), and big sagebrush (Artemisia tridentata Nutt.) had significantly less water when imbibed at 30°C than when imbibed at lower temperatures. The differences due to temperature suggest the relationship between imbibition temperature and seedling vigor is a general phenomenon related to the physiology of water uptake and to seed respiration (as indicated by weight loss). Therefore, we recommend that optimum imbibition temperatures be defined by species and incorporated into seed-testing guidelines. This appears particularly important for species that do not have a long history of cultivation and whose response to temperature may differ significantly from that of crops.