Using seed respiration as a tool for calculating optimal soaking times for 'on-farm' seed priming of barley (Hordeum vulgare)

Abstract

A low-cost technique named ‘on-farm’ seed priming is increasingly being recognised as an effective approach to maximise crop establishment. It consists of anaerobically soaking seeds in water before sowing resulting in rapid and uniform germination, and enhanced seedling vigour. The extent of these benefits depends on the duration soaking time. Current determination of optimal soaking time by germination assays and mini-plot trials is resource-intensive, as it is species/genotype-specific. This study aimed to determine the potential of seed respiration rate (an indicator of metabolic activity) and seed morphological changes during barley priming as predictors of the priming benefits and, thus, facilitate determination of optimal soaking times. A series of germination tests revealed that germination rate is mostly attributable to rapid hydration of embryo tissues as the highest gains occurred before the resumption of respiration. Germination uniformity, however, was not significantly improved until seed were primed for at least 8 h, i.e. after a first respiration burst was initiated. The maximum seedling vigour was attained when the priming was stopped just before the beginning of the differentiation of embryonic axes (20 h) after which vigour began to decrease (‘over-priming’). The onset of embryonic axes elongation was preceded by a second burst of respiration, which can be used as a marker for priming optimisation. Thus, monitoring of seed respiration provides a rapid and inexpensive alternative to the current practice. The method could be carried out by agricultural institutions to provide recommended optimal soaking times for the common barley varieties within a specific region.