Role of the lens in physical dormancy in seeds of Sophora alopecuroides L. (Fabaceae) from north-west China

Abstract

Although many studies have been done on seeds with physical dormancy, i.e. water-impermeable seed or fruit coat, the primary site of water entry into seeds after dormancy-breaking treatments is still controversial. In this work, the role of the lens in physical dormancy breaking was examined. The present study investigated the primary site of water entry and changes in seed-surface features for seeds of Sophora alopecuroides L. following various periods of scarification with sulfuric acid, hot-water treatments, and exposure to field conditions. Most seed coats first cracked in the hilum when pre-treated with sulfuric acid and after field exposure, but they cracked in both the hilum and extrahilar regions when treated with hot water. After pre-treatment, seeds first became slowly permeable in the hilum or extrahilar region and not in the lens. Acid scarification for 35 or 50 min caused the lens to crack, thus causing seeds to enter a fast imbibition stage. Seeds exposed to field conditions had further damage to the hilum, causing them to enter a fast imbibition stage. Imbibition time is a key point that determines the primary site of water entry into seed, and at least in part explains various results and interpretations about the role of the lens in physical dormancy in previous research.

Water absorption and dormancy-breaking requirements of physically dormant seeds of Sophora tomentosa L. and Erythrina speciosa Andr. (Fabaceae-Faboideae)

“…Furthermore, the immersion of scarified seeds into an aniline aqueous solution showed that the solution first entered the seed through the hilum. in agreement with these results, (Hu, Wang, Wu, Nan, & Baskin, 2008) observed in Sophora alopecuroides evidence of water intake through the hilum after sulphuric acid scarification of seeds (which showed a wider hilum fissure than non-scarified seeds) and in seeds buried in the field. However, they observed that depending on the time exposed to sulphuric acid, or in the field, the lens and extra-hilar region also become permeable to water.…”

“…This could be explained by the fact that the hilum and the lens are also involved in water absorption, but participate less than the micropyle at the beginning of imbibition, as proposed by Tailor (2005) for physically dormant Fabaceae seeds from Australian pastures. Difference in water uptake between different water gap has been also noted by Hu, Wang, Wu, Nan, and Baskin (2008) and Hu, Wang,Wu, and Baskin (2009). An interesting aspect of water imbibition observed in the present work, and already observed by Hu et al (2008) and Hut et al (2009), was the evidence that the water inlet region can be different between initial and subsequent soaking days.…”

“…Difference in water uptake between different water gap has been also noted by Hu, Wang, Wu, Nan, and Baskin (2008) and Hu, Wang,Wu, and Baskin (2009). An interesting aspect of water imbibition observed in the present work, and already observed by Hu et al (2008) and Hut et al (2009), was the evidence that the water inlet region can be different between initial and subsequent soaking days.…”

“…Both species showed seed morphological and anatomical features for seed coats of the subfamily Faboideae, as previously described by Corner (1976), Kelly, Van Staden, and Bell (1992) and Kirkbride, Gunn and Weitzman (2003), such as the lens close to the hilum, the hilum completely visible, and a funicular remnant (rim aril) that is split down the middle lengthwise. in S. tomentosa the micropyle is covered by the hilum as observed by Hu et al (2008) in S. alopecuroides. Lignin and callose, found around all palisade layer(s), are reported to be impermeable to water and would be responsible for the impediment of water absorption by the physically dormant seeds of Fabaceae (Baskin et al, 2000;Ma,Cholewa, Mohamed , Peterson, & Gijzen, 2004;Varela, & Albornoz 2013) suggest the permeability of Anadenanthera colubrina var.…”

Effects of sand burial, soil water content and distribution pattern of seeds in sand on seed germination and seedling survival of Eremosparton songoricum (Fabaceae), a rare species inhabiting the moving sand dunes of the Gurbantunggut Desert of China

“…PY prevents seeds from imbibing water even under favourable environmental conditions (Ballard 1976;Egley 1979;Rolston 1978) and significantly increases the seeds' lifespan. Thus, the seeds are distributed in time as well as in space, forming a persistent soil seed bank (Egley 1989), and PY may play a role in determining the time and place of seed germination in the field (Hu et al 2008). Most freshly matured E. songoricum seeds are physically dormant and thus cannot germinate.…”