Maataloustieteellinen A ikakauskirja Vol. 59: 387—396, 1987 The in vivo growth and development of micropropagated Elatior begonias (Begonia x hiemalis). I. Study on the effect of lighting and substrate. PÄIVI ROIVAINEN Department of horticulture, University of Helsinki, SF-00710 Helsinki, Finland Abstract. Micropropagation is an efficient way to produce pathogen-freeElatior begonias. However, certain problems arise when these plants are used in commercial pot plant produc- tion. The plants grow too luxuriantly, the root collars remain thin and flowering is delayed. To investigate the impact of the growing method, an experiment with different sources of supplementary light and different substrates was arranged in spring 1987. The following Elatior begonia cultivars were studied: ’Afrodite’, ’Afrodite Special’, 'Afrodite Rosa’, ’Man- dela’, ’Barbara’, ’Connie’, ’Marja’ and ’Sirene’. Four different lamp types were used: high- pressure sodium lamps (Airam SNaKd 330 W), high-pressure mercury lamps (Airam HgLX 400 W), high-pressure metal halide lamps (Philips HPI/T 375 W) and, as a control treatment, incandescent lamps of 100 W. The plants were potted in 82-peat (Sphagnum peat with moderate fertilization and medium sieving grade), 82-peat (3 parts) plus perlite (1 part) or 82-peat (2 parts) plus perlite (2 parts). The plants lighted with SNaKd or HgLX lamps were the highest, the broadest and the first to reach anthesis and the sale stage. The plants in the control group were the smallest and the last to reach anthesis and the sale stage. The effect of the substrate on the time re- quired to reach anthesis and the sale stage was clear only in the cultivar ’Afrodite Special’; when potted in peat-perlite 2 + 2, its plants flowered 2 weeks later than in other substrate mixtures. The height and the width of the plants were not greatly affected by the substrate. None of the lamp types or substrates clearly increased the number of flower buds or the diameter of the root collar. The proportion of saleable plants varied with the cultivar, lighting and substrate. In most cultivars it was below 50 %. The chief factors reducing saleability were luxuriant growth, weak flowering and oblique growth habit. Index words: Begonia x hiemalis, micropropagation, lighting, substrate. 1. Introduction Elatior begonia has become one of the most popular flowering pot plants in Finland. In 1986 almost 1,700,000Elatior begonias were 3 produced by 462 horticultural firms (Anon. 1987). Elatior begonias are traditionally pro- pagated by stem or leaf cuttings, a method which, unfortunately, enables pathogens to be transferred from one generation of plants to 387 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=VSxrwU0b3Cp6sMqj.P2gBUW2xWMnG8Z6fluC7BQ.eSggr2EbCqam9KA935d_6IZ9n6FqEl2KhEP2BtigT-sjBb0rfymQbHynRFKm1BuscMOJXR7pTcem1VIr_g8Gg070SpqWVWxB70GCL9G58DZa5LHGlW6FSXiri46OLEr0iL8dzy9uDb3HyJm_Z4ZWaCjAWYkRW0UJPAAqQYltBGQ_Tg another. One of the most serious diseases of Elatior begonia is bacterial leaf spot and blight caused by Xanthomonas begoniae. As no efficient chemical control of this disease is available at present, the only practical means of control is to prevent the spread of the disease. Micropropagation offers an efficient way to obtain healthy begonias at a high pro- pagation rate. The commercial growers have not, how- ever, been completely satisfied with the quality of micropropagated Elatior begonias. Ac- cording to them, the micropropagated plants grow too luxuriantly, the root collars remain thin and flowering is delayed compared with that of traditionally propagated plants. Due to the newness of this research field, very little information is available about the growth be- haviour of micropropagated Elatior begonias. The flowering of these begonias has been studied by Hildino and Welander (1976) and Bigot (1981). They report that no sig- nificant variation was evident in flower shape, size or colour in micropropagated plants, compared with those propagated traditionally. Welander (1978, 1987) investigated the growth of clones from different micropro- pagated Elatior begonia cultivars and the im- pact of the season on the development of micropropagated Elatior begonias, but he does not mention having noticed unwanted growth habits. The aim of this study was to investigate the growth and development of micropropagated Elatior begonias in supplementary lighting given by lamps with different spectral energy distributions and on substrate mixtures of dif- ferent nutrient content and nutrient-holding capacity. Studies on supplementary lighting of traditionally propagated Elatior begonias have been published by Hagen (1978) and Moe (1985). 2. Materials and methods Eight cultivars of Elatior begonia were used in this experiment: ’Afrodite’, ’Afrodite Spe- cial’, ’Afrodite Rosa’, ’Mandela’, ’Barbara’, ’Connie’, ’Marja’ and ’Sirene’. According to Hilding (1982), cultivars belonging to the ’Afrodite’ group and ’Mandela’ (’Ballerina’ group) have vigorous growth, ’Barbara’ and ’Connie’ (»Daehnfeldt» group) grow mode- rately, and ’Sirene’, belonging to the ’Nixe’ group, shows restrained growth. No informa- tion was found in the literature about the growth vigour of ’Marja’, but according to A. Pajunen (oral communication 24. 6. 1987), it belongs to the »Daehnfeldt» group. The experimental plants had been micro- propagated commercially and at the beginning of the experiment they were at the growth stage at which the commercial growers receive them, 4—lo cm high. Plants of every cultivar were divided into three groups according to the potting substrate to be used: group 1: 82-peat {Sphagnum peat with 0.95 % of 10—11.3—16-fertilizer and 6.2 % of dolomite lime by weight, medium sieving grade) group 2: 82-peat (3 parts) + perlite (1 part) group 3: 82-peat (2 parts) -I- perlite (2 parts) Perlite was used in order to obtain a lower nutrient content in the substrate just after potting. The plants were potted in 12 cm plastic pots and transferred to a greenhouse, where they were divided into four lighting groups, according to the lamp type to be used (different spectral energy distributions): group 1: Airam SNaKd 330 W (high-pres- sure sodium lamps) group 2: Airam HgLX 400 W (high-pressure mercury lamps) group 3: Philips HPI/T 375 W (high-pres- sure metal halide lamps) group 4: control (incandescent lamps 100 W) In lighting groups I—3 the amount of supplementary radiant energy was 5000 mW/ m 2 (± 10 ®/o), i.e. 1700—2200 lux at the level of the plant, depending on the lamp type. Group4 was a control group, receiving supple- mentary light of 150—200 lux at plant level in order to keep the plants vegetative. The lighting was started immediately after potting 388 on 16. 1. 1987 and was continued for 4 weeks, until 15. 2. 1987. The daily light-dark cycle was 16 hours light, 8 hours dark. After the lighting period, the plants received a short-day treatment of 2 weeks, during which the light-dark cycle was 8 hours light, 16 hours dark. There was no supplementary lighting. After the short-day treatment the plants were given light with incandescent lamps (150—200 lux) at 04.00—08.00 hours and at 16.00—20.00 hours, in order to pro- vide long-day conditions (16 hours), which promote formation and development of flower buds (Hilding 1982). Lighting was continued until 1. 4. 1987, after which the natural daylength was sufficient. The night temperatures during the different growing stages were intended to be as follows: vegetative period + 18°C, short-day treatment + 20°C and time to flowering + 18°C. In practice, however, these temperatures were difficult to keep and the night tempera- ture range observed was + 11—118°C (veg.), + 13—t-20°C (short-day) and + 13—f 18°C (flow.). Fertilizing was begun 3 weeks after potting. A fertilizer with 14 % N, 5 % P, 21 % K plus micronutrients was used. Nutri- ents were applied at every watering at the rate of 70 ppm N, 24 ppm P and 105 ppm K for one week and thereafter at the rate of 112ppm N, 38 ppm P and 168 ppm K throughout the experiment. No growth regulators were used. A randomized complete block design was used in this experiment with 6 replications. Observations were made at the beginning, at the end of the lighting treatment and from the beginning of anthesis to the end of the ex- periment. Height was measured from the pot rim to the highest peak of the plant. Width was determined as the average of two mea- surements at right angles to each other. The beginning of anthesis was determined as the date when the first open flower was noted. The sale stage was determined as the date when 7 flowers (’Afrodite’ group and ’Man- dela’), 6 flowers (’Barbara’, ’Connie’ and ’Marja’) or 5 flowers (’Sirene’) were open. The diameter of the root collar was measured on the top of the substrate from the first- flowering branch. The height and the width of the individual plants were recorded immediately after pot- ting and at the end of lighting. When a plant had reached the sale stage, the experiment was terminated for its part and the heigth, width, diameter of the root collar and saleability were observed. As there are no official require- ments concerning the saleability of Elatior begonias, a subjective judgement was made and thus the results in Table 10 are merely indicative. The whole experiment was ter- minated on 29. 5. 1987, i.e. 19 weeks after potting and 15 weeks after the beginning of the short-day treatment. An analysis of vari- ance was made and the means were separated by the use of an MSD, 5 % level. 3. Results 3.1. After lighting The results obtained after lighting are pre- sented in Tables 1 and 2. In most cultivars, plants lighted with SNaKd lamps and plants potted in peat showed the greatest increase in height and width. HgLX lamps generally in- duced more growth than HPI/T lamps, but the differences were not significant, except in the increase of width of the cultivar ’Afro- dite’. In most cases, plants grown under in- candescent lamps and plants potted in peat- perlite 2 + 2 had the poorest growth, though the plants under incandescent lamps were not the lowest. 3.2. At the sale stage Plants grown under SNaKd or HgLX lamps, depending on the cultivar, were the first to reach anthesis and the sale stage (Tables 3 and 4). The longest time tillanthesis and the sale stage was observed under incan- descent lamps. The differences between the lighting groups in reaching anthesis were 3—lo days and in reaching the sale stage 6—ll days, depending on the cultivar. Peat- 389 390 Table 1. Effect of lighting and substrate on the increase of height (cm) in Elatior begonias (4 weeks after potting). Cultivar Treatment 'Afrodite' 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 4.8a 4.9a 3.9a 3.6a 2.0a 3.8a 3.0a 2.2a 3.5 HgLX 400 W 4.0a 4.0a 2.9a 3.3a 2.6a 3.6ab 3.0a 2.1a 3.2 HPI/T 375 W 3.7a 3.8a 3.0a 2.8a 2.1a 3.oab 2.6a 2.4a 3.0 incandescent 100 W 4.2a 3.9a 3.8a 3.5a 2.3a 2.9b 3.0a 2.7a 3.3 Substrate: peat 4.1a 4.0a 3.9a 3.8a 2.6a 3.5a 3.1a 2.1a 3.4 peat-perlite 3 +1 4.4a 4.9b 3.3a 3.7a 2.4a 3.4a 3.0a 2.8a 3.5 peat-perlite 2 + 2 4.0a 3.6a 3.0a 2.5b 1.9a 3.0a 2.6a 2.2a 2.8 Cultivar mean 4.2 4.2 3.4 3.3 2.3 3.3 2.9 2.4 Means marked with the same letter in one column do not differ at the 5 % rate of error. Table 2. Effect of lighting and substrate on the increase of width (cm) in Elatior begonias (4 weeks after potting) Cultivar Treatment 'Afrodite' 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 7.7a 8.3a 5.8a 4.2a 5.0a 5.7a 5.2a 3.5a 5.7 HgLX 400 W 7.8a 7.6ab 5.9a 4.1a 4.0a 5.2ab 5.2a 3.3a 5.4 HPI/T 375 W 6.4b 6.2b 6.0a 3.3a 4.5a 4.9ab 4.2ab 3.1a 4.8 incandescent 100 W 5.8b 6.0b 5.3a 3.4a 4.2a 4.4b 4.0b 3.0a 4.5 Substrate: peat 8.2a 7.7a 6.3a 4.2a 5.2a 5.5a 4.8a 3.4a 5.6 peat-perlite 3 +1 7.3a 7.3a 6.oab 3.8a 4.4ab 5.3ab 4.9a 3.3a 5.3 peat-perlite 2 +2 5.4b 6.1b 5.0b 3.3a 3.9b 4.4b 4.4a 3.1a 4.4 Cultivar mean 6.9 7.0 5.8 3.7 4.5 5.1 4.7 3.3 Means marked with the same letter in one column do not differ at the 5 % rate of error. Table 3. Effect of lighting and substrate on the beginning of anthesis (days from the beginning of short-day treat ment) in Elatior begonias. Cultivar Treatment 'Afrodite' 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 37ab 56a 46a 54a 62a 38a 50a 48a 49 HgLX 400 W 33a 61a 43a 55a 66a 39a 46a 54a 50 HPI/T 375 W 37ab 61a 45a 58b 65a 40a 52ab 50a 51 incandescent 100 W 42b 61a 46a 59b 68a 48b 60b 54a 55 Substrate: peat 37a 55a 45a 56a 64a 42a 52a 54a 51 peat-perlite 3 + 1 36a 54a 44a 56a 64a 41a 48a 50a 49 peat-perlite 2 + 2 39a 70b 46a 58a 67a 41a 55a 50a 53 Cultivar mean 37 60 45 57 65 41 52 51 Means marked with the same letter in one column do not differ at the 5 % rate of error. Table 4. Effect of lighting and substrate on time taken to reach the sale stage (days from the beginning of short- day treatment) in Elatior begonias. Cultivar Treatment 'Afrodite' 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 58ab 77a 68a 66a 77a 56a 69ab 60a 66 HgLX 400 W 54a 79a 66a 66a 80a 57a 65a 65a 66 HPI/T 375 W 57ab 83a 67a 69a 79a 60a 68ab 63a 68 incandescent 100 W 63b 86a 72a 74b 84a 68b 76b 67a 74 Substrate: peat 57a 78a 68a 67a 76a 59a 69a 66a 68 peat-perlite 3+l 56a 78a 66a 66a 80a 60a 67a 63a 67 peat-perlite 2 + 2 61a 89b 70a 73b 83a 61a 73a 64a 72 Cultivar mean 58 82 68 69 80 60 70 64 Means marked with the same letter in one column do not differ at the 5 % rate of error. Table 5. Effect of lighting and substrate on the number of flowers and flower buds in Elatior begonias. Cultivar Treatment 'Afrodite' 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 45a 35a 40a 31a 55a 21a 19a 25a 34 HgLX 400 W 33a 31a 30a 32a 56a 20a 22a 32a 32 HPI/T 375 W 48a 36a 31a 31a 50a 22a 20a 24a 33 incandescent 100 W 39a 29a 30a 26a 48a 24a 22a 24a 30 Substrate: peat 42a 33a 33a 31ab 53a 22ab 22a 28a 33 peat-perlite 3+l 36a 33a 33a 32a 53a 24a 22a 26a 33 peat-perlite 2 + 2 44a 32a 33a 26b 51a 19b 18b 24a 31 Cultivar mean 41 33 33 30 52 22 21 26 Means marked with the same letter in one column do not differ at the 5 % rate of error. perlite 3 + 1 proved to slightly accelerate an- thesis and the sale stage. Peat-perlite 2 + 2 had the opposite effect in most cases. The dif- ferences between the substrate groups in reaching anthesis were 1 —l6 days and in reaching the sale stage 2—ll days, depending on the cultivar. In most cultivars, however, the differences were not significant. In the cul- tivar ’Afrodite Special’ potting in peat-perlite 2 + 2 strongly retarded anthesis and the sale stage. Fifteen per cent of the plants of ’Afrodite Special’, 4 °7o of ’Afrodite Rosa’ and 6 % of ’Marja’ had not reached the sale stage by the end of the experiment. The increase of height and width and the number of flowers and flower buds in these groups were as follows: Increase Increase No. of of height of width flowers and Cultivar (cm) (cm) flower buds ’Afrodite Special’ 15.8 ’Afrodite Rosa’ 11.7 ’Marja’ 11.1 1031.0 24.8 14 1216.5 The number of flowers and flower buds (Table 5) was not clearly dependent on the dif- ferent treatments. The measurements made at the sale stage 391 Table 6. Effect of lighting and substrate on the final increase of height (cm) in Elatior begonias. Cultivar Treatment 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 16.2 a 14.2 a 17.2 a 13.2 a 12.6 a 11.4 a B.Ba 13.8 HgLX 400 W 13.3b 12.6ab 16.0ab 12.7 a 11.9 a 10.6 a 8.9 a 12.6 HPI/T 375 W 15.2ab 14.0 a 14.5 b 11.3a 11.4ab 10.9 a 8.6 a 12.6 incandescent 100 W 12.4 b 11.3 b 11.9 c 12.2 a 10.2 b 10.2 a 7.2 b 10.9 Substrate: peat 13.4 a 12.9 a 16.2 a 12.1 a 12.0 a 10.0 a 8.6 a 12.5 peat-perlite 3 + 1 15.1a 13.3a 15.3a 12.6a 11.8ab 11.2 a 8.4 a 12.8 peat-perlite 2 + 2 14.3 a 12.8 a 13.2 b 12.5 a 10.9 b 11.2 a B.la 12.1 Cultivar mean 14.3 13.0 14.9 12.4 11.6 10.8 8.4 Means marked with the same letter in one column do not differ at the 5 % rate of error. showed that the height and width of theplants were increased most by SNaKd lamps and, in some cultivars, by HgLX lamps. Plants grown under incandescent lamps were the lowest and the narrowest. The differences between the substrate groups were not very pronounced and depended on the cultivar (Tables 6 and 8). A very significant interaction (F = 5.87 + + +) between lighting and substrate was noted in the increase of height in the cultivar ’Afrodite’ (Table 7). The diameterof theroot collar was not greatly affected by the different lighting and substrates, but in many cultivars it was greatest in plants lighted with HPI/T lamps and smallest in plants grown under in- candescent lamps (Table 9). The effect of a treatment on the proportion of saleable plants depended closely on the cultivar and showed great variation (Table 10). Table 7. Effect of lighting and substrate on the final in- crease of height in the Elatior begonia 'Afro- dite'. Treatment Increase of height (cm) SNaKd 330 W peat 18.7 a peat-perlite 3+ 1 15.2ab peat-perlite 2 + 2 15.3ab HgLX 400 W peat 13.5ab peat-perlite 3+ 1 16.0ab peat-perlite 2 + 2 14.2ab HPI/T 375 W peat 14.0ab peat-perlite 3+ 1 15.9ab peat-perlite 2 + 2 13.8ab Incandescent 100 W peat 13.3ab peat-perlite 3+l 12.1 b peat-perlite 2 + 2 10.9 b Mean 14.4 Means marked with the same letter in one column (all treatments) do not differ at the 5 "to rate of error. 392 4. Discussion The results obtained at the end of lighting show that plants lighted with SNaKd lamps were generally higher and broader than those in the other lighting groups. Light from SNaKd lamps contains a greater proportion of red wavelengths than light from HPI/T or HgLX, which is reported to cause elongation growth (Anon. 1973, Sandahl 1979). Hagen (1978) observed elongation in response to Philips SON/T, which is also a high-pressure sodium lamp. Moe (1985), however, obtained different results when growing Elatior be- gonias in a growth chamber. He reports that HPI/T caused more elongation thanSON/T. The elongation and poor increase of width in plants grown under incandescent lamps were natural consequences of the low light inten- sities. Table 8. Effect of lighting and substrate on the final increase of width (cm) in Elatior begonias. Cultivar Treatment 'Afrodite' 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 21.4a 25.0a 20.6a 15.8a 22.2a 12.5a 14.5a 10.3a 17.8 HgLX 400 W 18.2b 25.3a 17.3ab 15.9a 22.0a 11.6ab 12.5b 10.7a 16.7 HPI/T 375 W 18.0b 26.2a 18.9a 15.0a 21.3a 10.8ab 11.3b 9.9ab 16.4 incandescent 100 W 16.3b 24.0a 15.5b 14.4a 19.3a 9.9b 10.9b B.ob 14.8 Substrate: peat 18.8a 24.7a 18.3a 16.4a 21.3a 11.6ab 12.5a 10.0a 16.7 peat-perlite 3 + 1 18.1a 24.2a 18.1a 14.7a 20.9a 11.8a 12.2a 9.7a 16.2 peat-perlite 2 +2 18.5a 27.0a 17.9a 14.8a 21.5a 10.2b 12.2a 9.4a 16.4 Cultivar mean 18.5 25.2 18.1 15.3 21.2 11.2 12.3 9.7 Means marked with the same letter in one column do not differ at the 5 % rate of error. Table 9. Effect of lighting and substrate on the diameter of the root collar (mm) in Elatior begonias. Cultivar Treatment 'Afrodite' 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 5.6a 6.0a 5.2a 7.2a 6.0a B.oa 7.6a 6.5a 6.5 HgLX 400 W 5.5a 5.8a 5.2a 6.2bc 6.4a 8.3a 7.8a 6.7a 6.5 HPI/T 375 W 5.9a 6.2a 5.4a 6.9ab 6.6a 7.7a 7.9a 6.9a 6.7 incandescent 100 W 5.1a 5.4a 5.2a 5.9c 5.7a 7.5a 7.0a 6.2a 6.0 Substrate: peat 5.7a 5.7a 5.3a 6.8a 6.4a 7.9a 7.0a 6.3a 6.4 peat-perlite 3 +1 5.6a 6.1a 5.3a 6.9a 6.0a B.oa B.ob 7.0a 6.6 peat-perlite 2 + 2 5.3a 5.7a 5.0a 6.0b 6.1a 7.8a 7.7ab 6.4a 6.2 Cultivar mean 5.5 5.8 5.2 6.6 6.2 7.9 7.6 6.6 Means marked with the same letter in one column do not differ at the 5 % rate of error. Table 10. Effect of lighting and substrate on the proportion (%) of saleable plants in Elatior begonias. Cultivar Treatment 'Afrodite' 'Afrodite 'Afrodite 'Mandela' 'Barbara' 'Connie' 'Marja' 'Sirene' Treatment Special' Rosa' mean Lighting: SNaKd 330 W 28 0 44 67 50 50 22 88 43 HgLX 400 W 33 0 28 44 53 33 22 78 36 HPI/T 375 W 81 0 33 44 19 44 11 67 37 incandescent 100 W 50 6 50 39 47 33 39 44 38 Substrate: peat 62 4 38 46 57 29 29 67 41 peat-perlite 3 +1 54 0 42 54 38 46 12 74 40 peat-perlite 2 + 2 26 0 38 46 32 46 29 67 35 Cultivar mean 47 1 39 49 42 40 24 69 393 When observed 4 weeks after potting, plants potted in peat or peat-perlite 3 + 1 had generally grown better than plants potted in peat-perlite 2 + 2. This was to be expected, because the more perlite there was in the substrate mixture, the lower was the amount of available nutrients. The earliest flowering and arrival at the sale stage were obtained with SNaKd and HgLX lamps. Hagen (1978) also reports that high- pressure sodium lamps (SON/T) accelerate flowering, but Moe (1985) did not discover any notable differences between SON/T and HPI/T in this respect. The effect of the substrate on anthesis and arrival at the sale stage was most pronounced in the cultivar ’Afrodite Special’: anthesis began 2 weeks later in peat-perlite 2 + 2 than in other substrates. In most cultivars, however, the dif- ferences were not significant. At the sale stage, the highest and the broad- est plants were in most cases those grown under SNaKd lamps, which coincides with the results at the end of lighting. Surprisingly, the differences between the substrate groups did not increase, rather the opposite. It seems that regular fertilization, begun 3 weeks after potting, evened out the differences. The diameter of the root collar was not greatly affected by the different lighting or substrates. In plants of the vigorously growing cultivars, i.e. the ’Afrodite’ group and ’Mandela’, the root collars tended to be too thin to support the heavy crown and as a rule they needed sup- port. The thinness of the root collar is a spe- cial problem in micropropagated Elatior be- gonias and a cause of dissatisfaction among the commercial growers. The proportion of saleable plants varied greatly with the treatment and the cultivar. Hagen (1978) reports that different lamp types do not cause significant differences in the final appearance or quality of Elatior be- gonias. From the standpoint of commercial production, the total proportion of saleable plants in this experiment was rather low. The main factors reducing the saleability were long internodes, and leaf and flower stalks (’Afro- dite’), strong vegetative growth and weak flowering (’Afrodite Special’, ’Afrodite Rosa’ and ’Mandela’), an oblique growth habit, which means that the plants bend to one side and form a front and a back (’Barbara’, ’Con- nie’ and ’Marja’), and short flower stalks (’Sirene’). The long internodes, and leaf and flower stalks of the cultivar ’Afrodite’ could probably be overcome by using an appropriate growth regulator and lower temperatures. The short flower stalks of ’Sirene’ could be over- come by using higher temperatures. The choice of temperature can be a problem if cul- tivars of different growth vigour are grown in the same space. The abundant vegetative growth and the ob- lique growth represent more difficult prob- lems. Strong vegetative growth and branching caused a bushlike appearance and were con- nected with weak, delayed flowering. This was observed especially in the cultivar ’Afrodite Special’; 15 % of these plants failed to reach the sale stage before the experiment was ter- minated. It was often noticed that flowers and flower buds were formed only on the oldest branch and that the new, vigorous branches were completely vegetative. Oblique growth was not restricted to the vigorously growing cultivars with a heavy crown, in which it could be overcome by supporting the crown with a couple of sticks, but was also a problem in the cultivars ’Connie’ and ’Marja’, the plants of which were otherwise quite sturdy with thicker root collars. Oblique growth was not observed to be caused by the direction of the incoming daylight and the reason for this growth habit is not clear. Vigorous growth and delayed flowering are often reported to be the result of abundant fertilization. It is possible that, due to their healthiness, micropropagated Elatior begonias do not require as much fertilizer as the tradi- tionally propagated plants. There are also dif- ferences between cultivars in this respect. Another possible cause of strong vegetative growth could be theafter-effect of hormones or other substances used in the tissue culture media. Very little research has been devoted 394 to the after-effects of tissue culture media, possibly because micropropagation is a rela- tively new method. Further studies are needed to elucidate the reasons for the unwanted growth habits of certain micropropagated Ela- tior begonia cultivars. Acknowledgements. The author would like to thank the horticultural foundation of Nikolai and Ljudmila Borisoff for financial support, and OY Hortus AB for cooperation. 5. References Anon. 1973. Lighting in Greenhouses. Growelectric handbook n:o 2. 98 p. London. 1987.Puutarha-alan vuosikirja 1986. 96 p. Joensuu. Bigot, C. 1981. Multiplication vegetative in vitro de Be- gonia x hiemalis (’Rieger’ et ’Schwabenland’). 11. Conformite des plantes elevees en serre. Agronomic 1: 441—447. Hagen, P. 1978. Sammenligning av lysstoffror, hoy- trykkvikksolvhalogen- og hoytrykknatriumdamplam- per som tilleggslys til Hiemalisbegonia i vinterhalväret. Norges Landbrukshogsk., Inst, for blomsterdyrking og veksthusforsok, Meld. 213. Hildino, A. & Welander, T. 1976. Effects of some Factors on Propagation of Begonia X hiemalis in vitro. Swedish J. agric. Res. 6: 191 —199, 1982. Produktion av Begonia x elalior. Sveriges Lantbruksuniv., Konsulentavd. rapp., Trädgärd 220. Alnarp. Moe, R. 1985. Licht an fiir Jungpflanzen von Elatior- Begonien. Gb + Gw 85: 205—206. Sandahl, B. 1979. Belysning av växter. Sveriges Lant- bruksuniv., Konsulentavd. rapp., Trädgärd 176. Alnarp. Welander, T. 1978. In vitro Propagation of Clones from Different Cultivarsof Begonia x hiemalis. Swedish J. agric. Res. 8: 181—lB6. 1987. Odlingsförsök med mikroförökad Begonia x elalior hybr. ’Elfe’. Sveriges Lantbruksuniv., Kon- sulentavd. rapp., Trädgärd 318. Alnarp. Ms received October 5, 1987 SELOSTUS Mikrolisätyn pauliinabegonian (Begonia X hiemalis) kasvu ja kehitys in vivo. I. Valotukscn ja kasvualustan vaikutus. Päivi Roivainen Helsingin yliopisto, puularhatieteen laitos 00710 Helsinki Mikrolisäyksellä voidaan saada aikaan terveitä paulii-' nabegonian taimia. Niiden jatkokasvatuksessa on kuiten- kin ilmennyt ongelmia. Taimet rehevöityvät liikaa, nii- den juurenniska jää ohueksi ja kukinta viivästyy. Viljelytekniikan vaikutuksen selvittämiseksi järjestet- tiin keväällä 1987 valotus-ja kasvualustakoe seuraavilla mikrolisätyillä pauliinabegonialajikkeilla: ’Afrodite’, ’Afrodite Special’, ’Afrodite Rosa’, ’Mandela’, ’Barba- ra’, ’Connie’, ’Marja’ ja ’Sirene’, Kokeessa oli mukana neljä eri lampputyyppiä: suurpainenatriumlamput (Airam SNaKd 330 W), suurpaine-elohopealamput (Airam HgLX 400 W), monimetallilamput (Philips HPI/T 375 W) sekä kontrollina hehkulamput 100 W. Kokeessa mukana ol- leet kasvualustaseokset olivat 82-turve, 82-turve (3 osaa) plus perliitti (1 osa) sekä 82-turve (2 osaa) plus perliitti (2 osaa). SNaKd- tai HgLX-lampuilla valotetut taimet olivat kor- keimpia, leveimpiä sekä aloittivat kukinnan ja saavutti- vat myyntikuntoisuuden aikaisimmin. Kontrolliryhmän taimet olivat pienimpiä sekä kukkivat ja tulivat myynti- kuntoisiksi viimeisinä. Kasvualustaseosten vaikutus ku- kinnan alkamisen ja myyntikuntoisuudensaavuttamisen ajankohtaan näkyi selvästi ainoastaan ’Afrodite Special’ -lajikkeella, jonka turpeen japerliitin 2 + 2-seoksessa 395 kasvaneet taimet kukkivat 2 viikkoa myöhemmin muilla alustoilla kasvatettuihin taimiin verrattuna. Taimien kor- keuteen ja leveyteen eri kasvualustaseoksilla ei ollut ko- vinkaan suurta vaikutusta. Mikään lampputyypeistä tai kasvualustaseoksista ei muihin verrattunalisännyt selvästi kukkien ja nuppujen lukumäärää tai juurenniskan läpi- mittaa. Myyntikelpoisten kasvien osuus vaihteli suuresti lajikkeesta, valotuksesta ja kasvualustasta riippuen. Useimmilla lajikkeilla myyntikelpoisia kasveja oli alle puo- let kokonaismäärästä. Myyntikelpoisuutta vähensivät en- nenkaikkea liiallinen rehevyys, heikko kukinta ja vino kas- vutapa. 396