Bedding plants are an important part of the urban public space and private gardens. However, they are not always properly watered and suffer from drought stress, especially when grown in containers. In this trial a response to water stress of two commonly used species, impatiens (Impatiens walleriana Hook) and geranium (Pelargonium hortorum L. H. Bailey) were compared. The former is highly herbaceous and prone to wilting whereas the latter has hairy leaves and is better adapted to drought. Plants were grown at three levels of soil water content (SWC): 80% (control), 60% (mild stress) and 30% (severe stress). Drought was maintained during three 10 day cycles, separated by 10 day periods of normal watering. In both species roots were significantly longer in plants grown at 30% SWC as compared to 80% SWC while plant height and flower number were reduced by drought only in impatiens. The initial relative water content (RWC) was lower in geranium and decreased less in response to drought than in impatiens. Ammonium content in leaves of both species increased significantly under stress but the ranges of increase were different in both species. There was a significant increase in the free amino acids content in leaves of impatiens as compared to geranium but this rise was more time than drought dependent. The reduction in the a + b chlorophyll concentration in leaves of impatiens was significantly time and stress dependent while no reaction in geranium was observed. The above results show that changes in leaf RWC merit further attention as a possible indicator of plant response to drought stress in ornamental plants but additional studies are needed before this or other parameters can be used to evaluate new bedding plants for introduction into urban growing conditions, or as selection criteria in breeding for adaptation to demanding growing conditions.

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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

Recently peonies have become very popular cut flowers. As peony flowering period is short, long term cold storage could assure its prolonged supply and make long distance transport feasible. The effect of dry cold storage, of 8-hydroxyquinoline and nanosilver preservatives on the peony keeping qualities were tested on the most popular cultivar ‘Sarah Bernhardt’. The 12 week storage (0–1 °C) shortened flower longevity by 20%, to 8 days and no vascular blockages in the shoots were observed. However, the presence of callose, not considered as a blocking factor, was evident. The sucrose-containing preservatives with either 8-hydroxyquinoline or nanosilver did not extend the flower longevity but they increased flower diameters in both fresh and stored material. Generally, the soluble total and reducing sugars increased in senescing flowers in both non-stored and stored flowers, and they were lower after storage. The free proline increased ca. 20-times during cold storage and at the end of the vase life it remained generally higher in the stored than in fresh flowers. The level of hydrogen peroxide dropped after 12 weeks storage and its contents at the end of the vase life differed depending on the holding solution. Generally it was lower after storage. Storage increased the catalase activity which remained on higher levels in stored flowers from all holding solutions as compared to freshly cut flowers. A five-fold reduction in the peroxidase activity occurred during storage but its activities at the end of the vase life were similar in stored and non-stored flowers. The effects of nanosilver and 8-hydroxyquinoline were similar.

Peony is one of the most important ornamental plants in the international flower market, but has a relatively short vase life in water. This study tested the effects of 8-hydroxyquinoline citrate (8-HQC) and nanosilver (NS) in combination with sucrose, as well as two commercial preservatives, on the longevity and some physiological and biochemical aspects of senescence of cut flowers of 14 cultivars. Responses varied both by cultivar and treatment. The preservatives extended the vase life in only five cultivars; however, in nine cultivars, preservatives increased the flower diameter and improved the general flower appearance. Blockages in xylem vessels started to appear soon after harvest. Both NS and 8-HQC with sucrose prevented tylose formation, while bacterial blockages were reduced only by the NS solution. Reduction in stem blockages did not translate into better water balance or flower longevity. The highest carbohydrate accumulation in petals was observed in the NS solution. Preservatives mitigated the rise in free amino acids, including free proline. They did not prevent an increase in H2O2 content but flowers in preservatives generally had higher catalase activity than in the control. As solutions with NS produced comparable or even better results than 8-HQC, we recommend the latter as a component of a preservative for cut peony flowers. However, cultivar-specific responses indicate that postharvest treatments must be individually tailored to each cultivar.