Vol. 76, No. 2: 95-101, 2007 ACTA SOCIETATIS BOTANICORUM POLONIAE 95 STRATIFICATION CONDITIONS DETERMINING SEED DORMANCY RELEASE OF EUROPEAN BLADDER NUT (STAPHYLEA PINNATA L.) TADEUSZ TYLKOWSKI Laboratory of Seed Biology Institute of Dendrology, Polish Academy of Sciences Parkowa 5, 62-035 Kórnik, Poland e-mail: [email protected] (Received: May 29, 2006. Accepted: September 12, 2006) ABSTRACT European bladder nut has its northern limit in Poland and is legally protected. Climatic conditions, edible seeds attractive for small animals and seed dormancy to a large extent affect its restocking under natural conditions. The aim of this study was to determine conditions for seed dormancy release. Nuts dried after collection to ca 11% of moisture content (fresh weight basis) may be stored without loss of seed viability for over 1 year in a cold store at the temperature of -3°C. For the purpose of seed dormancy release nuts need to be stratified. Seed dormancy release was found highest after the application of warm-followed-by- cold stratification, first for 4-6 weeks at the temperature of 15°C or at cyclically alternating temperature of 10~20°C (24+24 h/cycle), followed by 16-18 weeks at 3°C. Seeds germinate at 3°C with the same rate as at cycli- cally alternating temperature of 3~15°C (16+8 h/day). Drying of nuts at room temperature to approx. 11% during the warm stratification phase (after 2 or 4 weeks) and further stratification resulted in a significant increase in seed germinability. In some seed lots scarification of nuts (dried during the warm stratification phase) contributes to a further significant increase of seed germinability. KEY WORDS: scarification; germination, sowing pretreatment. INTRODUCTION capsule (with 2-3 cases), with 1-4 (7) relatively large, ap- prox. 1 cm in diameter, hard, spherical nuts with a light European bladder nut (Staphylea pinnata L.) is a shrub brown and shiny coat. In English, bladder nut is named due of medium height, up to 5-6 (9) m high, yielding numerous to the appearance of the inflated capsule resembling the root suckers. In Poland this species is found rather rarely bladder. Seeds contained in the capsule may also resemble and is covered by strict legal protection. Bladder nut is hard pistachio seeds, thus in French bladder nut is called a thermophyte and most frequently occupies stands of sou- false pistachio (faux pistachier). Fragrant bladder nut thern exposure at the slope foot. Its geographical limit in flowers are white or pinkish, collected in abundant clu- Poland reaches its northern limit, south of 52° parallel. sters, blooming in May or June. They may be autogamous Under natural conditions it is found primarily in forests or entomophilous. and coppices, on limestone sites which do not dry during Oil pressed from nuts was used for lighting in former ti- the vegetation season, located in Silesia, on the Wieluñ- mes. Moreover, bells, rattles and rosaries were made from Czêstochowa Upland and more frequently in the Carpa- seeds with an attractive shiny coat. In the past bladder nut thian Foothills (Gostyñska 1961). Archeobotanical studies was cultivated in relation with magic properties ascribed to in Poland indicate a much broader range of bladder nut in it and used in religious rites and culture rituals (Cieciñski the Tertiary period (rodoñ 1992). Staphylea pinnata avo- 2004). To satisfy aesthetic and cultural needs plants were ids lowlands. It occurs in upland areas in river valleys of most frequently dug out and transferred from forests to be central and southern Europe, from southern France (The planted in the vicinity of houses and temples. For this rea- Vosges and Lorraine), to the Balkans in Bulgaria and Kra- son some archeologists are of the opinion that in places snodar on the Black Sea. where bladder nut is growing, remnants of former settle- The first element of the Polish common name [k³okocz- ments may be expected to be found (Lata³owa 1994). ka po³udniowa] refers to the characteristic rattle heard in The considerable weight of bladder nut seeds (Beranová autumn when the wind shakes twigs burdened with ripe and Benediková 2005) prevents its spread over farther di- fruits. The fruit of bladder nut is a leathery, inflated round stances. After falling to the ground they are willingly eaten 96 DORMANCY RELEASE OF STAPHYLEA PINNATA L. SEEDS Tylkowski T. by small animals. Only scarcely seeds grow into seedlings MATERIAL AND METHODS in the vicinity of maternal plants. Seeds may be dissemina- ted by squirrels (Browicz 1959). The introduction of blad- Several experiments were conducted in 2000-2004 at the der nut to large scale cultivation is prevented by the lack of Laboratory of Seed Biology of the Institute of Dendrology insight into methods of seed dormancy release, both in Po- PAS in Kórnik on seed dormancy release and germination land and other countries where this plant is found. in bladder nut. Four of these experiments are presented in The rare occurrence and scarce generative progeny of this study. Seeds for tests were collected at the permission bladder nut within its geographical limits were the reasons of the Minister of the Environment (permit no. BOA-A- why studies were undertaken to develop procedures of seed 135-2330/01/RP) at the beginning of October 2000 and handling to produce seedlings. In order to actively protect 2001 from several shrubs in the Dukla forest district and in an endangered species it is necessary to know first the con- 2001 in the Arboretum in Bolestraszyce. ditions of its propagation. It does not refer here to vegetati- Moisture content (MC) of nuts as a percentage of water ve propagation, connected with cloning and reduction of (fresh weight basis) was determined after their crushing gene pool. Ex situ protection in arboreta and botanical gar- and drying at the temperature of 105°C for 24 h. dens is only a partial solution to this problem. In available Results of laboratory seed germination were transformed literature there is very limited information on generative to arc sin Ö% and subjected to the MANOVA variance propagation of bladder nut. analysis using the Statistica (1997) programme and tested These scarce and frequently divergent pieces of informa- with the use of the Tukey test at the confidence level of tion contributed to our decision to undertake studies on the P=0.05. determination of optimum conditions of seed storage, do- rmancy release and germination of bladder nut. Germinability (%) A AB 15~25°C 3~20°C 11.3 fgh 11.3 fgh 8weeks 3°C o.g. B BB 15~25°C 3~20°C 16.7 efgh 20.0 def 12 weeks 3°C o.g. C CB 15~25°C 15~25°C 3~20°C 10.7 h 30.0 abc 4weeks 3°C 4weeks 3°C 2weeks o.g. D DB 15~25°C 15~25°C 15~25°C 3~20°C 20.7 cdef 34.0 ab 4weeks 3°C 4weeks 3°C 4weeks 3°C 2weeks 2weeks o.g. E EB 20~25°C 3~20°C 15.3 fgh 28.0 abcd 8weeks 3°C o.g. F FB 20~25°C 3~20°C 24.7 bcde 34.7 ab 12 weeks 3°C o.g. G GB 20~25°C 20~25°C 3~20°C 17.3 efgh 36.0 a 4weeks 3°C 4weeks 3°C 2weeks o.g. H HB 20~25°C 20~25°C 20~25°C 3~20°C 19.3 defg 32.0 ab 4weeks 3°C 4weeks 3°C 4weeks 3°C 2weeks 2weeks o.g. Means 17.0 L 28.2 K Fig. 1. Seed germinability corresponding to stratification thermal layout of Experiment 1. Symbols: A-H seeds not dried after collection; AB-HB seeds dried after collection; o.g. onset of seed germination. Results were tested using Tukeys T-test. Identical letters denote values which do not differ signifi- cantly at P=0.05. Vol. 76, No. 2: 95-101, 2007 ACTA SOCIETATIS BOTANICORUM POLONIAE 97 Experiment 1 Experiment 2 Non-dried nuts after being collected in 2000 (Dukla Forest Nuts from several shrubs were collected in October 2001 District), with the MC of 32.2% and nuts dried at room tem- in the Dukla Forest District. Empty nuts were isolated after perature to 11.3% were stratified in a substrate. As a substra- separation in alcohol and removed. Full nuts with MC of te a 1:1 (v/v) moist mixture of glass-sand with sieved peat 14.3% were stored in tightly closed containers from 17 with pH of 6.5 was used. Optimum substrate moisture con- October 2001 to 3 December 2002 at the temperature of tent was tested manually by squeezing in the hand a single -3°C. After storage nuts (in 3 replications 50 nuts each) drop of water should leak between fingers (Gordon and Ro- were used in the experiment (Fig. 2), the aim of which was we 1982, Suszka at all 1996). Nuts, in 3 replications of 50 to compare the effect on seed germination of the drying nuts each, were mixed with the substrate (1:3 v/v) and strati- procedure (for 3 days at room temperature) and drying and fied in a warm-followed-by-cold or warm-cold-warm-cold mechanical scarification after the completion of the warm systems, according to the design presented in Figure 1. phase of warm-followed-by-cold stratification at 15~25o/3°C During the warm phase of stratification cyclically alter- in the substrate. The applied stratification substrate was nating temperature was applied (under controlled condi- identical as in the previous experiment.