Planta (1984)162:566-568 P l a n t a 9 Springer-Verlag 1984 Short communication Gibbereilin-like activity in suspensors of Tropaeolum majus L. and Cytisus laburnum L. P. Picciarelli, A. Alpi*, L. Pistelli and M. Scalet Cattedra di Fisiologia Vegetale, Facolt~i di Agraria, Universit/t degli Studi di Pisa, Viale delle Piagge, 23, 1-56100 Pisa, Italy Abstract. Gibberellins in the embryo-suspensor system have been considered so far only in Phaseo- lus coccineus. We present in this report the localiza- tion of gibberellin-like substances in the suspensors of Tropaeolum majus L. and Cytisus laburnum L. The total gibberellin activity (expressed as gibber- ellic-acid equivalent in the c~-amylase bioassay) in 2000 suspensors (106 mg fresh weight; FW) of C. laburnum and in 600 suspensors (236 mg FW) of T. majus were 50.9 gg g- 1 FW and 8.9 gg g- 1 FW respectively. Key words: Cytisus - Embryo (suspensor) - Gib- berellin (suspensor) - Suspensor - Tropaeolum. The suspensor of the higher plant is a short-lived embryonic organ which connects the developing embryo to the maternal tissue; it originates from basal cells of the first division of the zygote, where- as the terminal cell develops into the embryo- proper. 'In-vitro' studies demonstrate that the em- bryo needs the suspensor for its early development (Nagl 1974; Cionini et al. 1976; Yeung and Sussex 1979). Recent studies indicate that the suspensor is involved in the translocation of nutrients to the embryo (Yeung 1980). Some authors (Corsi 1972; Ponzi and Pizzolongo 1972; Nagl 1974; Alpi et al. 1975) attributed to the suspensor one important physiological function, namely the synthesis of growth substances. The presence of auxin in the suspensor of Tro- paeolum majus L. was reported by Przybyllok and Nagl (1977). The presence of gibberellin (GA)-like and cytokinin-like substances was ascertained in * To whom correspondence should be addressed Abbreviation : GA = gibberellin the suspensor of Phaseolus coccineus (Alpi et al. 1975; Lorenzi et al. 1978). More recently, GA 1 has been identified in the suspensor of P. coccineus at the early developmental stage (Alpi et al. 1979, and Ceccarelli et al. 1981) clearly indicate that the sus- pensor is active in the biosynthesis of gibberellins. In this work we report the presence of GA-like substances in the suspensor of two other species, T. majus and Cytisus laburnum L. The choice of these two species has been determined by the fact that both species have a massive suspensor, a fea- ture which emphasises its functional role. In partic- ular, T. majus suspensors takes the form of haus- toria which penetrate into the endosperm, the inte- guments and the micropyle (Maheshwari 1950). Cytisus laburnum, like P. coccineus, is a legume while T. majus belongs to the Tropeaolaceae. The suspensors from developing seeds of T. majus and C. labur- num were dissected under a stereoscopic microscope and imme- diately frozen at -20 ~ C. Frozen suspensors, 2000 (106 mg fresh weight; FW) from C. laburnum and 600 (236 mg FW) from T. majus, were homog- enized in cold 80% aqueous methanol and stirred for 12 h at 2~ before centrifugation at 2500 g for 10 rain. The residue was re-extracted twice. The combined filtrates were reduced to the aqueous phase and the pH adjusted to 2.5. The aqueous phase was then parti- tioned three times against ethyl acetate and the ethylacetate extract was dried (MgSO4) , filtered, and reduced to a small volume. An aliquot of the extracts was directly bioassayed. Silica-gel partition chromatography was carried out as pre- viously described (Alpi et al. 1979). After elution, the column was washed twice with 20 ml methanol each time; the fractions obtained are referred to as C 1 and C z. Gibberellin activity was detected using the barley-endosperm bioassay (Jones and Varner 1967). Figures i and 2 show the results of bioassaying 1 1 --50 and ~ dilutions of the fractions which had been eluted from silica-gel columns for T. majus and C. laburnum, respectively. These results clearly in-