Ab stractIn or der to im prove veg e ta tive prop a ga tion of a dif fi cult to root Cotinus coggygria the stock plants were sub jected to: eti o lation, shad ing and spray ing with IBA, com bined with the ap plica tion of two com mer cially avail able root ing pow ders. The IBA treat ment was more suit able for root ing of C. coggygria cut tings than the NAA ap pli ca tion and it en hanced rhizogenesis re gard less of the form of auxin ap pli ca tion (fo liar appli ca tion to a stock plant or a root ing pow der used di rectly on cut tings) and the amount of light pro vided to stock plants. Eti ola tion did not im prove rhizogenesis in stem cut tings, how ever, re duc tion of light in ten sity by 50 % and 96 % of the am bi ent prior to har vest of cut tings af fected root ing pos i tively. Pos i tive ef fects of shad ing can be as cribed to changes in shoot anat omy, i.e. a weaker sclerenchyma de vel op ment. Syn er gis tic ef fect of shad ing and fo liar auxin ap pli ca tion can re sult from the increase in leaf blade area and/or thin ner lower epiderm. Enhanced root ing in cut tings from shoots grown out un der reduced light in ten sity was ac com pa nied by de crease in the contents of to tal sol u ble sug ars, sol u ble pro teins and free ABA and by in crease in to tal chlo ro phyll, free amino ac ids, polyphenolic ac ids and free IAA con tents. In tro duc tionVegetative prop a ga tion is par tic u larly im por tant in or na men tal hor ti cul ture where cultivars are of ten het ero zy gous and prop a ga tion from seeds does not en sure pres er va tion of char ac ter is tic dec o ra tive traits. Prop a ga tion by stem cut tings is one of the most com monly used meth ods in pro duc tion of orna men tal shrubs (Hartmann et al. 1997). How ever, many cultivars of both co nif er ous and leafy spe cies are dif fi cult to prop a gate by cut tings (Hartmann et al. 1997). There fore, new methods to intensify rooting are searched for. Stimulation of rhizogenesis by the plant hor mone auxin has been known since 1935 (Zimmerman and Wilcoxon) and com mer cial root ing pow ders contain ing auxins are com monly used. How ever, plants dif fer in their re sponse to ex og e nously applied auxins. Among the three syn thetic auxins (IBA, NAA and 2,4-D) IBA shows the broad est spec trum of ac tion (Mac don ald 1989). Our ear lier ex per i ments showed that fo liar auxin ap pli ca tionboth to cut tings (Szydło and Marczyński 1998) or to stock plants prior to cut ting har vest (Pacholczak et al. 2005) im proves root ing of or na men tal shrubs prop a gated by cut tings. The use of eti o la tion to improve root ing dates from 1961 when Frolich tried to im prove av o cado prop a ga tion by grow ing stock plants in dark ness. How ever, us ing plas tic foil to cover the stock plants may re sult in plant dam ages as both tem per a ture and hu mid ity rise ex ces sively un der such con di tions (Howard 1984). Shad ing 417 ACTA PHYSIOLOGIAE PLANTARUM

De part ment of Or na men tal Plants, Fac ulty of Hor ti cul ture and Land scape Ar chi tec ture, War saw Ag ri cul tural Uni ver sity, Nowoursynowska 159, 02-776 Warszawa, Po land Key words: root ing, IBA, shoot anat omy, chlo rophyll, sol u ble pro teins, to tal sol u ble sug ars Ab stractIn or der to im prove veg e ta tive prop a ga tion of Berberis thunbergii 'Red Rocket', stock plants were sub jected to shading and IBA treat ment, as well as to the ap pli ca tion of two com mer cially avail able root ing pow ders. Spray ing stock plants with IBA 24 hours prior to cut ting har vest gave the effect com pa ra ble to the use of root ing pow ders. Re duc tion of light in ten sity by 50 % and 96 % of am bi ent prior to har vest of cut tings im proved root ing. Pos i tive ef fect of shad ing re sults in changes in shoot anat omy, i.e. a weaker sclerenchyma de velop ment. En hanced root ing in cut tings from shoots grown under re duced light in ten sity was ac com pa nied by a de crease in the con cen tra tion of sol u ble pro teins and by an in crease in to tal chlo ro phyll con tent while the con cen tra tion of to tal sol u ble sug ars re mained un af fected. In tro duc tionBerberis shrubs are widely used in gar dens and parks be cause of their dec o ra tive value and wide adapt abil ity to en vi ron men tal con di tions. The plants have to be prop a gated vege ta tively as prop aga tion through seed does not en sure pres er va tion of the char ac ter is tic dec o ra tive traits of the cultivars. Prop a ga tion by stem cut tings is one of the most com monly used meth ods in the pro duc tion of or namen tal shrubs (Hartmann et al. 1997). How ever, to sat isfy a grow ing de mand for the or na men tal plant ma te rial and to re duce the costs of nurs ery pro duction, the im proved meth ods to in ten sify root ing are de sir able. Stimulation of rhizogenesis by the plant hor mone auxin has been known for 70 years (Zimmerman and Wilcoxon 1935) and root ing pow ders con taining auxins are com monly used in com mer cial produc tion of or na men tal shrubs. Our ear lier ex per iments showed that fo liar auxin ap pli ca tion -both to cut tings (Szydło and Marczyński 1998) and to stock plants prior to cut ting har vest (Pacholczak et al. 2005 a) im proved root ing of cut tings from or namen tal shrubs.Eti o la tion is known to im prove root ing ever since Frolich (1961) at tempted to im prove av o cado propa ga tion by grow ing stock plants un der dark ness. Re duced light in ten sity can af fect shoot anat omy: lig ni fi ca tion of shoots is weaker and less sclerenchyma de vel ops, there fore, less of a bar rier to growth of root primordia is cre ated (Caesar 1990, Nicolini et al. 2001. How ever, in stead of cov er ing stock plants with non trans par ent (black) plas tic foil, shad ing with air-per me able nets would yield prop a gat ing ma te rial with better phys i o log i cal param e ters (Har ri son-Murray and Howard 1982).