Effects of various pretreatments on seed germination ofCalystegia soldanella (Convolvulaceae), a coastal sand dune plant

Abstract

We tested various pretreatments to enhance the germination of 'Sea bells' (Calystegia soldanella Roem. et Schult).One experiment, which improved the germination rate by 70%, involved first scarifying the seed coats, then immersing the seeds in 50 ppm GA3 for 24 h. A GA3-alone pretreatment did not increase germination. However, the most effective method, with a 100% success rate, included 3 h of acid pretreatment with 98% H2SO4. We also used scan. ning electron microscopy (SEM) to examine the seed-coat surfaces and cross-sections of dry seeds. SEM showed structural differences between seeds that were not treated and those exposed to 98% H2SO4. The latter treatment allowed the seed coats to crack and break, thereby disrupting their physical dormancy.Keyword: Calystegia soldanella, GA3, H2SO4, scarification, seed germination, SEMThe Calystegia soldanella plant (Sea bells; Convolvulaceae) is endemic to coastal sand dunes. It blooms from May to June, and the seeds ripen in August. Its subterranean stems are used as a traditional diuretic medicine. Those long stems also allow the plants to retain sandy soils, making this species ideal for the restoration of coastal dunes and erosion control. Despite its great value in ecological preservation, it has been difficult to maintain appropriate habitats for C. soldanella because interference from human activities has caused the loss of coastal dunes. To solve these problems, the populations of sand dune species, e.g., C. soldanella, Elyrnus mollis, and Carex kobomugi, must be perpetuated. For example, several methods are available for propagating C. soldanella, including by seed, tissue and cell culture, and cuttings.Various chemical strategies can improve seed germination rates, such as the application of gibberellic acid (Miyoshi and Sato, 1997; Bhattacharya and Khuspe, 2001;Puppala and Fowler, 2002;Padilla and Encina, 2003), sulfuric acid (Ishikawa et al., 1993; Sozzi and Chiesa, 1995;Demel, 1998), and potassium nitrate (KNO3) (Bungard et al., 1997;Kang et al., 2001). In addition, one can use hydrationdehydration treatments (Ren and Tao, 2003), scarification (Baes and Viana, 2001), or smoke and heat (Morris et al., 2000;Tieu et al., 2001) to increase success.Seed dormancy can be caused by either embryo immaturity or poor imbibition of water and gas exchange through the seed coat. In the latter case, such as with C. soldanella, dormancy can be broken by treating those hard coverings. The function of the seed coat is to protect the embryo and endosperm from desiccation, mechanical injury, unfavorable temperatures, and attacks by bacteria, fungi, and insects (Bhojwani and Bhatnagar, 1978).In the present study, we investigated the most effective methods for enhancing in vivo germination of C. soldanella by pretreating seeds with gibberellic acid, sulfuric acid, or scarification. We also observed the external and cross-sectional structures of the seed coat via scanning electron microscopy. MATERIALS AND METHODS Seed CollectionSeeds of C. soldanella were collected in August and...

Environmental filtering drives the shape and breadth of the seed germination niche in coastal plant communities

“…Conversely, of the nine species with a preference for the highest germination temperature (30/20 C), seven are beach plants. Two of the shifting dune species which we did not include in the niche analyses due to their low germinability (Calystegia soldanella and Eryngium maritimum) have also been reported to germinate with summer temperatures (Walmsley and Davy, 1997;Ko et al, 2004;Di Sacco and Bedini, 2015). The estimated best temperature for germination in cliffs is one degree above winter day temperatures, while in beaches it corresponds to average summer day temperatures.…”

“…After collection, seeds spent 3 weeks in the laboratory (21 C, 50 % relative humidity) before seed cleaning and the start of the germination experiments. Because physical seed dormancy was expected in Calystegia soldanella (Ko et al, 2004) and Lavatera arborea (Santo et al, 2015), seeds of these two species were mechanically scarified before further manipulation.…”

Dormancy, germination requirements and storage behaviour of seeds ofConvolvulaceae(Solanales) and evolutionary considerations

“…Studies on Merremia species (Sharma and Sen, 1975;Azania et al, 2003), Calystegia soldanella (Kondo et al, 2001(Kondo et al, , 2002Ko et al, 2004), Convolvulus spp. (Brown and Porter, 1942;Koller and Cohen, 1959;Weaver and Riley, 1982;Tamak et al, 1994;Gonzalez-Martin, 1998) and Jacquemontia spp.…”

“…ornamental species of Ipomoea (Hardcastle, 1978; Horak and Wax, 1991; Ogunwenmo, 2006) and Merremia (Azania et al , 2003) and the weedy species Ipomoea spp. (Misra, 1963; Chandler et al , 1977; Norsworthy and Oliveira, 2007), Convolvulus arvensis (Brown and Porter, 1942; Weaver and Riley, 1982; Tamak et al , 1994), Calystegia soldanella (Kondo et al , 2000; Ko et al , 2004), Evolvulus alsinoides (Saharan et al , 2001) and Cuscuta campestris (Hutchison and Ashton, 1980; Benvenuti et al , 2005). In their review of the biology and control of weedy Ipomoea spp., Elmore et al (1990) suggested that seeds of morningglory species are dormant due to a water-impermeable seed coat, and they reported that most of them require high temperatures to germinate.…”

Direct and indirect interactions of native and introduced species in coastal habitats

“…soldanella's seeds and the species is acknowledged as an important fore-dune species, which is able to trap sand to a certain extent (Ko et al 2004).…”