Cynanchum bungei Decne (Baishouwu in China), a member of the Asclepiadaceae family, is a perennial climbing shrub distributed in China. Its root has been used as a tonic medicine or health food for centuries in traditional Chinese medicine. C. bungei has useful activities including antitumor and immune regulatory effect and is non-toxic (Gao et al., 2005). As a rare, endemic, and beneficial species, C. bungei is becoming more and more precious not only in China, but also in other countries such as Japan and Korea (Song et al., 2006).
C. bungei is grown mainly by cuttings and root propagation and seldom by seed propagation. With the increasing demand for this endangered wild resources (Zhang et al., 2010), seed propagation can be used to solve supply and demand, protect germplasm resource, and enrich genetic diversity of this species.
Environmental factors such as light and temperature are known to affect seed germination in Asclepiadaceae family. Seeds of Calotropis procera and Leptadenia pyrotechnica are quick germinating and do not have strict requirements for light and temperature conditions, whereas seeds of Cryptostegia grandiflora and Pergularia daemia are slow germinating and exhibit optimum germination in dark at ≈30 °C (Sen, 1968). Seeds of Asclepias tuberosa and Asclepias viridiflora germinate well at 21 °C and light is not an influencing factor (Norman, 1993). Seeds of Matelea maritima germinate at an optimum temperature of 25 °C in light, the process being optimized by alternating temperatures of 25/35 °C (Cuzzuol and Lucas, 1999). Also, light requirement for germination can vary with temperature (Smith, 1982).
Seed size is a factor that is associated with seed germination and seedling growth (Farhoudi and Motamedi, 2010). Studies of the relationship between seed size and seed germination and seedling performance have provided various results. A positive relationship between seed size and seed germination and seedling performance has been found within seed lots in a number of studies (Benard and Toft, 2007). In saline soils, smaller seeds of safflower and chickpea germinate faster and have better seedling performance compared with larger seeds (Farhoudi and Motamedi, 2010; Kaya et al., 2008). In different populations of the dimorphic Tragopogon pratensis subsp. pratensis, larger seeds yield higher germination percentage, yet no relationship has been found between seed size and seedling growth (Mölken et al., 2005).
Previous studies suggested that most of these factors show diverse effects on seed germination and seedling growth characteristics of different species. Information about C. bungei seed germination is lacking. The objectives of the study were to investigate seed germination and early seedling growth responses of C. bungei to photoperiod, temperature, and seed size to determine seed propagation requirements, develop standard germination procedures, and provide conservation strategies for C. bungei.
BaskinC.C.BaskinJ.M.1998Seeds: Ecology biogeography and evolution of dormancy and germination. Academic Press San Diego CA
BenardR.B.ToftC.A.2007Effect of seed size on seedling performance in a long-lived desert perennial shrub (Ericameria nauseosa: Asteraceae)Intl. J. Plant Sci.16810271033
BewleyJ.D.BlackM.1994Seeds: Physiology of development and germination. Plenum Press New York NY
BoyleT.H.HladunK.2005Influence of seed size, testa color, scarification method, and immersion in cool or hot water on germination of Baptisia australis (L.) R. Br. seedsHortScience4018461849
BretagnolleF.ThompsonJ.D.LumaretR.1995The influence of seed size variation on seed germination and seedling vigour in diploid and tetraploid Dactylis glomerata LAnn. Bot. (Lond.)76607615
FarhoudiR.MotamediM.2010Effect of salt stress and seed size on germination and early seedling growth of safflower (Carthamus tinctorius L.)Seed Sci. & Technol.387378
GaoL.J.WangJ.H.CuiJ.H.WangH.Z.2005Studies on immunoregulation of polysaccharides-1a from Radix Cynanchi BungeiChina J. Chin. Mater. Med.3013521355
HuJ.ZhuZ.Y.SongW.J.WangJ.C.HuW.M.2005Effects of sand priming on germination and field performance in direct-sown rice (Oryza sativa L.)Seed Sci. & Technol.33243248
KayaM.KayaG.KayaM.D.AtakM.SaglamS.KhawarK.M.CiftciC.Y.2008Interaction between seed size and NaCl on germination and early seedling growth of some Turkish cultivars of chickpea (Cicer arietinum L.)J. Zhejiang Univ. Sci. B5371377
LeishmanM.R.WestobyM.1994The role of seed size in seedling establishment in dry soil conditions—Experimental evidence from semi-arid speciesJ. Ecol.82249258
MohsenM.N.MahdiB.AbolfazlT.2011Effect of seed size and genotype on germination characteristic and seed nutrient content of wheatSci. Res. Essay.620192025
MölkenT.V.Jorritsma-WienkL.D.HoekP.H.W.V.KroonH.D.2005Only seed size matters for germination in different populations of the dimorphic Tragopogon pratensis subsp. Pratensis (Asteraceae)Amer. J. Bot.3432437
NormanC.D.1993Seed germination theory and practice 2nd ed; (1996) First supplement; (1998) Second supplement. Norman C.D. State College PA
RebeccaW.D.1984The effect of seed size and maternal source on individual size in a population of Ludwigia leptocarpa (Onagraceae)Amer. J. Bot.7113021307
SenD.N.1968Ecology of desert plants and observations on their seedlings. II. Germination behaviour of seeds in AsclepiadaceaeÖsterr. Bot. Z.1151827
SongZ.G.WangJ.H.WangH.Z.ZhaoA.H.LiuC.X.TianJ.C.2006Some properties of starch isolated from Radix Cynanchi bungeiStarch-Stärke58243248
SuskoD.J.Lovett-DoustL.2000Patterns of seed mass variation and their effects on seedling traits in Alliaria petiolata (Brassicaceae)Amer. J. Bot.875666
WulffR.D.1986Seed size variation in Desmodium paniculatum. II. Effects on seedling growth and physiological performanceJ. Ecol.7499114
ZhangF.YuS.L.WangJ.H.2010Studies on the photosynthetic characteristics and its relationship to yield in Radix Cynanchum bungei DecneJ. Nuclear Agr. Sci.24176180