Seed Science Research http://journals.cambridge.org/SSR Additional services for Seed Science Research: Email alerts: Click here Subscriptions: Click here Commercial reprints: Click here Terms of use : Click here A comprehensive view of epicotyl dormancy in Viburnum furcatum: combining eld studies with laboratory studies using temperature sequences Shyam S. Phartyal, Tetsuya Kondo, Akinori Fuji, Siti N. Hidayati and Jeffrey L. Walck Seed Science Research / Volume 24 / Issue 04 / December 2014, pp 281 - 292 DOI: 10.1017/S0960258514000257, Published online: 28 August 2014 Link to this article: http://journals.cambridge.org/abstract_S0960258514000257 How to cite this article: Shyam S. Phartyal, Tetsuya Kondo, Akinori Fuji, Siti N. Hidayati and Jeffrey L. Walck (2014). A comprehensive view of epicotyl dormancy in Viburnum furcatum: combining eld studies with laboratory studies using temperature sequences. Seed Science Research, 24, pp 281-292 doi:10.1017/S0960258514000257 Request Permissions : Click here Downloaded from http://journals.cambridge.org/SSR, IP address: 133.50.190.252 on 16 Nov 2014 Seed Science Research (2014) 24, 281–292 doi:10.1017/S0960258514000257 q Cambridge University Press 2014 A comprehensive view of epicotyl dormancy in Viburnum furcatum: combining field studies with laboratory studies using temperature sequences Shyam S. Phartyal1,2*, Tetsuya Kondo1, Akinori Fuji1, Siti N. Hidayati3 and Jeffrey L. Walck3 1Graduate School of Agriculture, Hokkaido University, Sapporo, Japan; 2Department of Forestry and NR, H.N.B. Garhwal Central University, Srinagar-Garhwal, Uttarakhand, India; 3Evolution and Ecology Group, Department of Biology, Middle Tennessee State University, Murfreesboro, TN 37132, USA (Received 21 December 2013; accepted after revision 14 July 2014; first published online 28 August 2014) Abstract Keywords: cotyledon emergence, epicotyl dormancy, morphophysiological dormancy, radicle emergence, Seeds with epicotyl dormancy reside in soil up to temperature sequences, Viburnum 15 months (or longer), being exposed to a sequence of temperatures, before seedlings completely emerge (i.e. with both roots and shoots). Heretofore, few studies have examined precise temperatures, Introduction especially in sequences, for promotion of radicle and cotyledon emergence and how they relate to environ- Most kinds of dormancy in seeds that readily imbibe mental cues in nature. Viburnum is the best known water are broken by one type of treatment – usually genus to exhibit epicotyl dormancy and, as such, we warm stratification (after-ripening) or cold strati- investigated the Japanese V. furcatum, hypothesizing fication – and radicles and cotyledons emerge a similar kind and level of dormancy. The under- simultaneously (Baskin and Baskin, 1998). Epicotyl developed embryos in mature seeds in October were dormancy is an exception. In this dormancy, the spatulate shaped, unlike those in other Viburnum radicle emerges in response to a dormancy-breaking species, and they elongated from late June to August environmental cue but the epicotyl remains dormant of the following year. Radicles emerged after embryo for a few to several weeks until it is exposed to another growth until mid-October, followed by cotyledons dormancy-breaking environmental cue. In the deep, from mid-April to mid-May. Temperatures required for simple epicotyl morphophysiological dormancy embryo growth, radicle and cotyledon emergence in (MPD), warm stratification is required for the under- the laboratory approximated closely those in the field. developed embryo to elongate inside the seed for Embryo elongation and radicle emergence occurred at radicle emergence, and then cold stratification is warm temperature regimes, and gibberellic acid (GA3) needed for cotyledon emergence from seeds with an did not substitute for this warm temperature require- emerged radicle. In contrast, in seeds with non-deep, ments. Following a 120-d cold stratification of seeds simple epicotyl MPD, cotyledons require either a with an emerged radicle, shoots emerged from seeds period of warm stratification (Baskin et al., 2008) or at 10, 15, 15/5, 20/10 and 25/158C. We identified that a very short period of cold stratification (Dhyani et al., seeds of V. furcatum have deep simple epicotyl 2013) to emerge from seeds with an emerged radicle. morphophysiological dormancy like the majority of Epicotyl dormancy is also known to occur in seeds other Viburnum species. For propagation of the with fully developed embryos, which do not need to species from seeds, the nearly 2-year period for grow inside the seed before radicle emergence seedling emergence could be shortened to 8 months: (Jayasuriya et al., 2010, 2012). start fresh seeds at 25/158C (60 d) and then move them Regardless of whether the embryo is under- or fully through a sequence of 15/58C (30 d) ! 08C (120 d) developed, seeds with epicotyl dormancy reside in the ! 20/108C (30 d). soil for a relatively long time before seedlings emerge completely (i.e. with both roots and shoots). For example, complete seedling emergence takes 7 months *Correspondence for Cimicifuga racemosa or 11 months for Gagea lutea with Fax: þ 91 1370 267529 late summer or late spring seed dispersal, respectively Email: [email protected] (Baskin and Baskin, 1985; Kondo et al., 2004), 282 S.S. Phartyal et al. and 15 months or longer for Viburnum acerifolium or V. commonly in the understorey of Fagus crenata climax opulus with late autumn dispersal (Hidayati et al., 2005; forests on the mountains of Japan (Hukusima et al., Walck et al., 2012). During this time, seeds are exposed 1995) and it regenerates by vigorous sprouting from to a natural sequence of temperatures. Previous buds at the base of the stem (Yamanaka and Tamai, studies that have investigated the requirements to 1986; Hara, 1990). Plants of this species growing in overcome epicotyl dormancy: (1) incubated seeds over closed-canopy conditions have greatly reduced fruit a set (often narrow) of single constant or alternating production compared with those in gaps (Hara et al., temperatures; (2) stratified seeds at one temperature 1991). Fruits of V. furcatum are an important and then incubated them at a different temperature; component in the diet of Japanese black bears and/or (3) used a move-along experiment (Takagi, (Selenarctos thibetanus japonicus) during summer 2001; Adams et al., 2003; Mondoni et al., 2009; Copete months (Nozaki et al., 1983). Therefore, regeneration et al., 2011; Mattana et al., 2012). In a move-along of this species along forest edges and in gaps should be experiment, a cohort of seeds is moved through a encouraged. However, to our knowledge, no infor- sequence that simulates the duration and tempera- mation is available on how to regenerate this species tures of seasons from dispersal until radicles and then from seeds, especially the requirements for seed cotyledons emerge. This type of experiment has dormancy break and germination. Thus, knowledge become a standard practice among biologists studying of seed germination ecology is necessary, if the species epicotyl dormancy, especially since it approximates is to be used for restoration programmes. the phenology of embryo growth, and radicle and In this study, we first documented the timing of cotyledon emergence, in nature. embryo growth and of radicle and cotyledon emer- A couple of studies on epicotyl dormancy have gence outdoors. To this end, we correlated these varied the temperature sequences (albeit to a limited phenological events to recorded temperatures and amount) to better understand precisely which observation on snow accumulation throughout the temperatures in an appropriate manner promote 21-month field study. Next, we performed a series of emergence of root or cotyledon. Kondo et al. (2005) laboratory experiments. We conducted a move-along showed that radicle emergence in Corydalis ambigua experiment to follow a cohort of seeds through an (Fumariaceae) was earlier and higher in seeds moved ‘annual’ temperature sequence starting in at a summer ( ! ) through a sequence of 25/15 ! 15/5 ! 08C regime. We hypothesized that, like the majority of than a sequence of 10 ! 58C. Baskin et al. (2009a) other Viburnum species, seeds of V. furcatum may also found that hypocotyl (which eventually produced a require a warm summer temperature for embryo root) and cotyledon emergence of Daphniphyllum growth and radicle emergence after seed dispersal in glaucescens (Daphniphyllaceae) was much earlier and autumn, and a cold winter temperature for shoot slightly greater for seeds given a sequence of 15/6 emergence. We then examined the specific temperature ! 20/10 ! 25/15 ! 20/108Cthan5/1! 15/6 ! requirements for embryo growth, radicle emergence 20/10 ! 25/158C or 25/15 ! 20/10 ! 15/6 ! 20/108C. and cotyledon emergence by using single constant Thus, responses of seeds vary depending on the and alternating temperature regimes, and by using temperature sequence. sequences of 2–5 temperatures varying in duration. Among plant genera, Viburnum (Adoxaceae; APG Two other experiments were done to determine: (1) the III, 2009) is the best known to exhibit epicotyl dormancy, effects of gibberellic acid (GA3) on radicle emergence; with seeds of most species having deep, simple epicotyl and (2) the duration of cold stratification required MPD (Baskin et al., 2009b; Moura and Silva, 2010; Chien to promote cotyledon emergence. Using this infor- et al., 2011; Walck et al., 2012). Moreover, members of this mation, we could also determine whether seeds