Summary
Sodium hypochlorite (NaOCl) can release dormancy of imbibed wild oat (Avena fatua L.) seeds. Treatments found effective included (i) immersing intact seeds in 800 mm NaOCl for 1 h followed by incubation on 5 × 10−4m gibberellin A3(GA3); (ii) immersing dehulled seeds in 800 mm NaOCl for 1 min followed by incubation on 5 × 10−4m GA3; (iii) immersion of dehulled seeds in much lower concentrations of NaOCl, e.g. 13 4 mm for 3 h followed by incubation on water; or (iv) incubating dehulled seeds on a low concentration of NaOCl. Based on the concentrations of each of the reagents required to produce equivalent responses, NaOCl is approximately 4–6 times more effective than hydrogen peroxide (H2O2) in triggering the onset of germination, and 6 times as effective in causing growth inhibition in the roots. These results suggest the modes of action of NaOCl and H2O2 in the termination of dormancy reside in a modification of the properties of the hull and seed coat membranes, and in the provision of additional oxygen to the seed.

Actions of sodium hypochlorite and hydrogen peroxide on seed dormancy and germination of wild oats, Avena fatua L.

Witchweed [Striga asiatica (L.) Kuntze] seeds conditioned for 3 weeks in either water or 0.01% (w/v) sodium hypochlorite (NaOCl) had 83 to 95% germination after being treated with dl-strigol, kinetin, zeatin, or natural stimulants from corn (Zea mays L.) root exudates. None of these compounds, however, induced germination of seeds conditioned in 0.025 or 0.050% (w/v) NaOCl. Seeds conditioned in 0.075, 0.1, or 0.15% (w/v) NaOCl had 8, 56, and 76% germination, respectively, during the first week of conditioning and 10, 100, and 100% germination after 2 weeks of conditioning. Germination in these concentrations of NaOCl was termed “atypical”.

Effects of sodium hypochlorite and certain plant growth regulators on germination of witchweed (Striga asiatica) seeds [Weed].

The present study aims to identify factors of importance to the extrapolation from laboratory toxicity test to field effects using copper and black bindweed as a model. In the laboratory the influence of Cu on seed germination and seedling survival was studied in both soil spiked with Cu in the laboratory and soil collected at a Cu-polluted site. Maternal effects were also studied. We found that seeds from Cu-stressed plants germinated more readily after a short, cold storage than control seeds, but no differences were found after a longer storage. The low germination of control seeds compared to maternal treated seeds could not be attributed to differences in thickness of the seed coat. Germination was slightly stimulated at 232 mg Cu kg−1. At the highest Cu level (i.e. 1,330 mg Cu kg−1) only 5% of the seeds germinated. Mortality of the seedlings increased with increasing Cu concentration reaching 40% at 391 mg Cu kg−1. At higher concentrations mortality decreased. Germination was not affected in laboratory tests with soil from a Cu-polluted site, but the biomass of the plants decreased with increasing Cu concentration. The distribution of the plants on a Cu-polluted site was registered in relation to soil Cu concentration. Cu was analyzed using three different extractors, i.e. HNO3, CaCl2, and DTPA. The distribution of the plant in the field was predicted from calculated lifetime effect of a given Cu soil concentration based on the laboratory tests. The results revealed that growth is more sensitive in the field than should be expected from laboratory tests due to several stressors in the former situation. Bioavailability was lower in the field soil but this was counteracted by the increased effect. Incorporating bioavailability in the prediction of field effects thus reduced the fit of the model and bioavailability measures could not be further evaluated.

Effects of soil copper on black bindweed (Fallopia convolvulus) in the laboratory and in the field

Chun, S.-C., Schneider, R. W., and Cohn, M. A. 1997. Sodium hypochlorite: Effect of solution pH on rice seed disinfestation and its direct effect on seedling growth. Plant Dis. 81:821-824. Bacteria were completely eliminated from rice seeds following immersion in household bl each solutions (50% bleach and 2.6% NaOCl) adjusted to pH 7.0 in 0.5 M potassium phosphate, while fungi were eliminated at pH 5.0 and below. Mercuric chloride was used to disinfest nondormant rice seeds in order to test the direct effect of sodium hypochlorite on rice seedling growth apart from an indirect effect related to elimination of microbial contaminants. Seeds were immersed for 2 h in each solution or water in each of the following treatments: (i) sterile water followed by sterile water, (ii) HgCl 2 (1,000 µg/ml) followed by sterile water, ( iii) HgCl2 followed by KH2PO4 (0.3 M), (iv) HgCl2 followed by NaOCl, and (v) NaOCl followed by sterile water. Sodium hypochlorite solutions were prepared in 0.3 M potassium phosphate, which gave a final pH of 7.3. Seedling growth in treatments in which seeds were treated with HgCl 2 followed by NaOCl, and NaOCl followed by sterile water, was significantly greater than those treatments in which seeds were treated with sterile water followed by sterile water, HgCl 2 followed by sterile water, and HgCl 2 followed by KH2PO4. Sodium hypochlorite stimulated rice seedling growth directly, as opposed to an indirect effect related to elimination of microbial contaminants or alleviation of dormancy.

https://apsjournals.apsnet.org/doi/pdfplus/10.1094/PDIS.1997.81.7.821

Sodium Hypochlorite: Effect of Solution pH on Rice Seed Disinfestation and Its Direct Effect on Seedling Growth

In natural conditions one or more of the following factors may operate to convert a seed from the dormant to the non-dormant (i.e. germinable) state: (a) light, (b) temperature, (c) ageing, (d) changes in the covering structures. In the following account we will discuss these factors in detail. Numerous other experiences and treatments can also be shown to break dormancy, largely under laboratory conditions. In this category come many chemicals (e.g. nitrate, cyanide, malonate, various growth substances) and several physical treatments (e.g. high oxygen pressures, seed coat removal, coat abrasion by various means). Some of these are unlikely to be of importance in nature, although they should not be ignored since they can help us to understand possible mechanisms involved in the maintenance and ending of dormancy. We will therefore consider them later in this chapter.

The Release from Dormancy

Seed germination of wild buckwheat (Polygonum convolvulus L.) and cow cockle (Saponaria vaccaria L.) increased with increasing time of immersion in 6% sodium hypochlorite (NaOCl). Maximum germinati...

The effect of sodium hypochlorite, gibberellic acid, and light on seed dormancy and germination of wild buckwheat (Polygonum convolvulus) and cow cockle (Saponaria vaccaria)

A. I. Hsiao

Papers

The effect of sodium hypochlorite, gibberellic acid, and light on seed dormancy and germination of wild buckwheat (Polygonum convolvulus) and cow cockle (Saponaria vaccaria)