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DEVELOPMENTAL BIOLOGY/MORPHOGENESISInduction of adventitious shoot regenerationin chrysanthemum as affected by the seasonMa?gorzata Zalewska & Justyna Lema-Rumińska &Natalia Miler & Magdalena Gruszka & Weronika D?balReceived: 1 December 2009 /Accepted: 19 October 2010 /Published online: 17 November 2010 / Editor: M. Cheng# The Society for In Vitro Biology 2010Abstract The subject of investigation was Chrysanthemumx grandiflorum (Ramat.) Kitam., FSatinbleu_. Leaf explantsand internodes were excised from the middle part of thedonor sterile plant. Two methods of explant inoculationwere applied: explants were placed polarly and horizontal-ly. Modified MS medium (Murashige and Skoog 1962),supplemented with 11.4 μM indoleacetic acid and 2.7 μM6-benzylaminopurine, were prepared to induce adventitiousbud formation. Four dates of explant inoculation on themedium were tested: January 15, April 15, July 15, andOctober 15. Thus, regeneration occurred in winter, spring,summer, and autumn. In the present study, a more intensiveregeneration in FSatinbleu_ chrysanthemum was observedin summer and autumn than in spring and winter,irrespective of the kind of explant and the inoculationmethod.Keywords Chrysanthemum x grandiflorum (Ramat.)Kitam. . Regeneration . Biological rhythmIntroductionAdventitious shoot regeneration in chrysanthemum in vitrois important mostly in creating new cultivars, both inmutation breeding (Broertjes et al. 1976; Jerzy andZalewska 1996; Zalewska and Jerzy 1997) and in separat-ing chimera components (Zalewska et al. 2007), as well asin genetic transformation (Nahid et al. 2007).Adventitious shoot regeneration in chrysanthemum invitro is affected by many factors: the composition of themedium applied, growth regulators interaction, the kind ofexplant, plant genotype, and the developmental stage of thestem explant (Lu et al. 1990; Lee et al. 1997; Himstedt etal. 2001; Nahid et al. 2007). When inducing mutation, aclear effect of ionizing radiation and its dose on theregeneration of adventitious shoots can be observed (Jerzy1989; Zalewska and Lema-Rumińska 2004). Also, theseason seems to be an important factor determining thenumber of adventitious shoots and thus the regenerationeffectiveness (Nahid et al. 2007).Biological rhythms which occur in nature can be dividedaccording to their duration: circadian, lasting from 20 to28 h, most often 24 h; infradian—longer than 28 h; andultradian—shorter than 20 h (Sweeney 1963; El-Morsy andMillet 1996; Webb 2003; Goldbeter 2008). In nature, youcan most often find circadian rhythms connected with therotational movement of the Earth and, consequently, withthe daily rhythm of light and darkness as well as, indirectly,with changes in temperature. Many aspects of plantphysiology are related to that rhythm; e.g., the growth oforgans or stomatal movements, and at the molecular level,the biochemical or transcriptional activity (Webb 2003).El-Morsy and Millet (1996) observed the occurrence ofinfradian rhythmic growth during micropropagation fromaxillary buds in Citrus aurantium L. in culture in vitro,isolated from the natural daily cycle. However, there are noreports on the effect of circannual rhythms as a factor ofplant growth and development in vitro.The aim of the present study was to determine whetherthe season plays an essential role in adventitious shootregeneration in vitro in chrysanthemum.M. Zalewska : J. Lema-Rumińska (*) : N. Miler : M. Gruszka :W. D?balLaboratory of Biotechnology, Department of Ornamental Plantsand Vegetable Crops, University of Technology and Life Sciences,Bernardyńska 6,PL-85-029 Bydgoszcz, Polande-mail: lem-rum@utp.edu.plIn Vitro Cell.Dev.Biol.—Plant (2011) 47:375–378DOI 10.1007/s11627-010-9330-7