Tetraploids of daylily have taken a leading position among the daylily cultivars due to desirable traits such as vigorous growth and flowers with more intense colour. In our previous studies, several tetraploids of daylily cultivars 'Blink of an Eye' and 'Berlin Multi' were obtained using in vitro techniques with different antimitotic agents (colchicine, oryzalin, trifluralin, and amiprophos methyl). The purposes of this study were to evaluate changes in daylily tetraploids in relation to their diploid counterparts and to assess variation among diploids and tetraploids derived from genetically homogenous plant material treated with antimitotic agents. In the first year of the ex vitro cultivation, growth of tetraploids was poorer in comparison with diploids, but in the second year, tetraploid growth was much more vigorous. Compared to diploids, in tetraploids of both cultivars percentage of flowering plants was lower, flowering was delayed by 8 days and 1 month in 'Blink of an Eye' and 'Berlin Multi', respectively, and bud number per scape was lower by approximately 20 and 40 %, respectively. Tetraploid leaves and flowers of both cultivars were significantly larger, chlorophyll concentration index was higher by approximately 40 %, and stomata were longer by 35 %. In 'Berlin Multi' tetraploids, inflorescence stems were shorter by 20 %. In 'Blink of an Eye', variation in flower colour tone and shape and stamen malformation rate was detected both within the unconverted diploids and tetraploids but was more evident in tetraploids. In both cultivars, variation was also found in the nuclear DNA content, which ranged in diploids and tetraploids, respectively, 8.02-8.53 and 16.01-17.13 pg in 'Berlin Multi ' and 8.28-8.71 and 15.93-17.36 pg in 'Blink of an Eye'. Since the variation, while less evident, also occurred in the diploids (regenerated from the antimitotic treated material), we suppose that these variations could be due to antimitotic agents that can induce not only chromosome doubling but also chromosomal and gene mutations. The extent and character of these changes can be related to parental genotype and/or antimitotic agent. Further research is required at the cytological and molecular level to explain the character of changes, epigenetic and/or genetic.
The ad ven ti tious shoot re gen er a tion from pet i ole explants of Pelargonium × hederaefolium 'Bonete' was achieved via a mixed path way i.e. organogenesis and so matic embryogenesis. The histological study of re gen er ated structures re vealed the pres ence of both shoot primordia and embryo-like struc tures. The ini tial growth in pet i ole explants occurred on me dia with BAP + auxin or TDZ alone. How ever, the most ef fec tive re gen er a tion (24 struc tures/explant) was noted in the pres ence of TDZ (2 mg·l -1 ) and IBA (0.1 or 0.2 mg·l -1 ). More over, the ap pli ca tion of TDZ in the in duc tion phase reduced the time needed for the for ma tion of ad ven ti tious structures and pos i tively in flu enced the fur ther shoot de vel op ment on the me dium con tain ing m-topolin and IBA.
List of ab bre vi a tions:BAP -N 6 -benzylaminopurine; IAA -indole-3-ace tic acid; IBA -indole-3-bu tyric acid; MS -Murashige and Skoog me dium; mT -(meta-topolin)-N 6 -(3-hydroxybenzyl) ad e nine; TDZ -thidiazuron (N-phenyl-N'-1,2,3-thiadiazol --5-ylurea)
In tro duc tionPelargonium is one of the most im por tant bed ding and pot plant in the world. Cur rently, the ma jor produc ers and dis trib u tors of pelargonium plants are North Amer ica and Eu rope. Out of four com mercially im por tant groups (Pelargonium × hortorum L. H. Bailey -P. zonale hort., P. × domesticum L. H. Bailey -P. × grandiflorum hort., P. × hederaefolium -P. peltatum hort. and scented ge rani ums) the most pop u lar in North Amer ica are cultivars of P. × hortorum, which are in high percent (50 %) prop a gated by seed (Lange and Horn 1996). In Eu rope, P. × hortorum and P. × hederaefolium, mostly prop a gated vege ta tively by cut ting, are bought in the same pro por tion. The basic fac tors be ing a req ui site of a prof it able mass pro duc tion are: breed ing, new cul ti va tion tech nology and, first of all, healthy star t ing ma te rial. The need for patho gen-free plants as the elite mother stock led to the de vel op ment of in vi tro prop a ga tion sys tem. How ever, be cause of the spe cific re quirements of dif fer ent ge no types for a me dium com posi tion (min er als, or ganic com pounds and growth reg u la tors) an op ti mal and uni ver sal method of Pelargonium sp. micropro pa ga tion has not been elab o rated yet. A suc cess ful re gen er a tion of plants from dif fer ent ini tial explants both via organogenesis or embryogenesis was widely reported for P. × hortorum cultivars (Abo El-Nil and 255 ACTA PHYSIOLOGIAE PLANTARUM
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