Physiological Basis of Achene Dormancy in Polygonum convolvulus (Polygonaceae)

Abstract

Germination of dormant achenes of wild buckwheat (Polygonum convolvulus L.) was promoted at 25 C if they were stratified at low temperatures. Preincubation at either 2 C or 10 C promoted subsequent germination at 25 C equally, although the period of time to reach maximum germination was shorter for the 2 C treatment. Moreover, a preincubation treatment of a daily alternating cycle 2 C for 20 hr and 10 C for 4 hr promoted germination at 25 C more than either temperature alone. Removing portions of the hard pericarp and testa did not promote germination of dormant achenes at 25 C except when the portion of those structures covering the tip of the radicle was removed. This suggests that the structures covering the embryo do not prevent germination by restricting the movement of water or gases but rather restrict growth mechanically. Complete removal of the pericarp promoted germination, but much higher germination was obtained when the testa was also removed, indicating that the pericarp may not be the main factor in dormancy. Thus the role of low temperature in the loss of dormancy in wild buckwheat achenes may be to promote the production of hydrolytic enzymes that lower the mechanical resistance of pericarp and testa and/or increase the embryo growth potential beyond some threshold level and thereby enable the radicle to overcome the resistance to growth imposed by the structures covering the embryo.

Karymorphological and molecular studies on seven species in Polygonoideae (Polygonaceae) in Egypt

“…Our results are consistent Fig. 1 with those of Metzger (1992) where treatment of seeds with concentrated sulfuric acid coupled with low temperature induced the germination of Polygonum and Persicaria. Seeds responded to the acidifi cation by concentrated sulfuric acid at low temperature (10 °C) yielding high germination rates.…”

“…At this temperature panel that mimics the natural conditions at which these plants grow, germination started after 1-3 weeks. Metzger (1992) suggested that seed dormancy is due to either embryo-covering structure that might prevent gas exchange and\or water uptake or the presence of germination inhibitors. Therefore, different strategies were established to overcome seed dormancy in Polygonaceae: 1) removal of the pericarp portion of Polygonum seeds by exposure to low temperatures (Metzger 1992); 2) applying both cold and acid stratifi cation to destabilize the embryo-covering structures (Al-Helai 1996); 3) cold stratifi cation and gibberellic acid to lyse the hard covering structures; 4) treatment with enzymes to lyse the pericarp (Daniels 1998;Al-Turki et al 2000); 5) exposure to different physiological factors such as temperature, light, pH, seed age and soil depth, to optimize germination conditions (Yilmaz et al 2007).…”

“…In the Polygonaceae, the plants suffer from seed dormancy by unknown reasons (Metzger 1992) and consequently they are diffi cult to germinate in the laboratory. In conditions of natural environment, those seeds germinate by seasonal fl uctuation of temperature (Roberts and Totterdell 1981;Pye and Andersson 2009) but light appeared to be not critical for germination (Bouwmeester and Karssen 1992).…”

“…Stoppage of seed dormancy The collected seeds were subjected to two different treatments; acidifi cation and low-temperature stratifi cation simultaneously. Seeds were fi rstly sterilized by soaking in diluted NaOCl at noninhibitory concentration for 5 min (Oyebanji et al 2009;Talei et al 2011) (Metzger 1992).…”

Effect of phylogeny, life history and habitat correlates on seed germination of 69 arid and semi-arid zone species from northwest China

“…physical dormancy (Baskin and Baskin 1998;Jayasuriya et al 2007). Evidence from the literature suggests that seeds of Eragrostis pilosa (Li et al 2006), Plantago depressa (Yu et al 2004), the three species of Nitrariaceae (Nitraria tangutorum, N. praevisa, N. sphaerocarpa), four species of the six Zygophyllaceae species (Peganum harmala, P.nigellastrum, P. multisectum and Zygophyllum mucronatum) (Wang, ''unpublished data''), and six of the eight Polygonaceae species (Polygonum argyrocoleum, P. aviculare, P. lapathifolium, P. sibiricum, Atraphaxis bracteata, Calligonum potanini) (Metzer 1992) have physiological dormancy. Various other members of Asteraceae, Amaranthaceae, Poaceae, Solanaceae may have had some physiological dormancy.…”