Effect of hypoxia on buried weed seed germination

Abstract

Summary Trials were carried out in order to investigate the effect of hypoxia on seed germination of Datura stramonium L. in Petri dishes and when buried at various depths in soil. Hypoxia was found to cause a decrease in germination capacity and germination rate. This inhibition was partially alleviated by daily exchange of hypoxic gas surrounding the seeds during incubation. Similarly, seed scarification allowed maintenance of a higher germination capacity under conditions of low oxygen availability, showing that the seed coat was only partially gas permeable. Oxygen deficiency led to a decrease in respiratory capacity. However, this was probably compensated for by induction of fermentation metabolism. The possibility of removing the final products of fermentation exerts a decisive influence on seed germination, especially in an environment such as soil, where their diffusion into the surrounding environment is restricted. Thus daily nitrogen flushing partially eliminated this inhibition, even under conditions of low external oxygen availability. It was therefore postulated that the main depth–derived inhibition was not caused directly by oxygen deficiency but by the increasing difficulty in eliminating toxic fermentation products, which was found to be proportional to the degree of hypoxia. Finally, incubation for several days under completely anaerobic conditions induced secondary dormancy. This was probably due to an ecological adaptation mechanism that prevents germination under conditions that are unfavourable for survival.

Which soils are comfortable for oilseed rape seeds (Brassica napus) to survive?

“…Hypoxia is another factor which can induce dormancy (Benvenuti and Macchia 1995, Pekrun et al 1997, Momoh et al 2002. Sandy soils with greater pore volume and gas exchange facilitated emergence of Datura stramonium, whereas emergence was inhibited by clay soils (Benvenuti 2003).…”

Ecophysiology and respiratory metabolism during the germination of Inga sessilis (Vell.) Mart. (Mimosaceae) seeds subjected to hypoxia and anoxia

“…Exceptions are the species (Kennedy et al 1991) and Datura stramonium L. (Benvenutti & Macchia 1995).…”

Seedbank reduction after different stale seedbed techniques in organic agricultural systems

“…In particular, it has been noted (Terpstra, 1995) that compaction of soil aggregates plays a crucial role in germination inhibition. Alhough the ecophysiological causes of this phenomenon have not yet been fully clarified, it is probably due to poor soil gas diffusion (Benvenuti and Macchia, 1995). Other studies have shown that in such conditions even phytochrome activation (of photosensitive seeds) by light stimuli becomes ineffective (Benvenuti and Macchia, 1997).…”

“…Preservation of seeds in the soil is also favoured by the frequent limitations on key germination factors such as temperature (Vleeshouwers, 1997), water (Forcella, 1993), light (Taylorson and Handricks, 1983) and oxygen (Benvenuti and Macchia, 1995). The latter factor is thought to be strongly involved in the germination trigger as a result of aereation created through soil tillage.…”