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 recognized as an effective approach to maximize 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 soaking time. The 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 the seed respiration rate (an indicator of metabolic activity) and seed morphological changes during barley priming as predictors of the priming benefits and, thus, facilitate the determination of optimal soaking times. A series of germination tests revealed that the germination rate is mostly attributable to the rapid hydration of embryo tissues, as the highest gains in the germination rate occurred before the resumption of respiration. Germination uniformity, however, was not significantly improved until seeds were primed for at least 8 h, that is, 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 axis elongation was preceded by a second respiration burst, which can be used as a marker for priming optimization. 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.

Optimization of ‘On Farm’ Hydropriming Conditions In Wheat: Soaking Time And Water Volume Have Interactive Effects On Seed Performance

“…In the present study, the first 4 hours of soaking resulted in a significant improvement in germination speed compared to dry seed (64 percent out of total 84 percent improvement at 20°C; 51 percent out of total 69 percent improvement at 25°C). These findings are consistent with a study in which length of on-farm priming was standardized in barley seeds 14 . In this study, it was determined that the rapid boost in germination speed after a few hours of priming is mostly related to the first rapid hydration of seed tissues, whereas developmental advancement is the primary source of improvements at longer soaking times.…”

“…Under all three volume treatments, about half of the water was absorbed within 8 hours. This is a feature of the phase I 'imbibition' stage and shows the fast hydration of interior seed tissues 14 . As imbibition is essentially a passive process that serves as a catalyst for the resumption of metabolic activity, the priming period must be long enough to ensure that germination processes are sufficiently advanced to allow for pre-germinative effects to take place.…”

“…The outcomes of 'onfarm' seed priming under varied climatic conditions are mostly influenced by two major criteria for quick germination: (1) the level of hydration of the seed; (2) the advantages of developmental advancement over dry seeds at the time of sowing. Rapid hydration of interior tissues is the primary cause of faster germination in primed seeds 14 . In the present study, the first 4 hours of soaking resulted in a significant improvement in germination speed compared to dry seed (64 percent out of total 84 percent improvement at 20°C; 51 percent out of total 69 percent improvement at 25°C).…”

Modelling the Effect of Salt and PEG on Water Uptake in Wheat Seeds

“…Previous studies have reported that seed priming-soaking seeds in water for between 10 and 24 h prior to planting leads to improvements in germination percentages and plant establishment, as well as the subsequent vigour, disease resistance and ultimately yield of crop plants in semi-arid tropical areas [1,28]. It seems plausible that improved water and carbohydrate availability during germination and seedling establishment may at least partially explain these observations [29].…”

Optimization of ‘on farm’ hydropriming conditions in wheat: Soaking time and water volume have interactive effects on seed performance

“…Under all three volume treatments, about half of the water was absorbed within 8 hours. This is a feature of the phase I ‘imbibition’ stage and shows the fast hydration of interior seed tissues [ 21 ]. As imbibition is essentially a passive process that serves as a catalyst for the resumption of metabolic activity, the priming period must be long enough to ensure that germination processes are sufficiently advanced to allow for pre-germinative effects to take place.…”