[Morphological studies on direct regeneration of floral buds from in vitro cultures of sepal segments in Sinningia speciosa hiern].

The morphological changes in the cultures of sepal segments in Sinningia speciosa Hiern were observed with Zeiss Stemi 2000-C Stereomicroscope from 0 to 65 days after culture in vitro. The light yellow globular protuberances were observed on the cut edge and the surface of sepal segments after culture for 24 days. Then the globular protuberances grew bigger gradually. A lot of floral buds on the surface of sepal segments formed after culture for 60 days. The morphological changes in the cultures of sepal segments were studied with light microscopy after culture for 0 to 30 days as well. The cells of tissues of sepal segments arranged regularly and no dividing cell was observed on the first day culture. There appeared some small meristematic centers of dividing cells on cut edge and the lower epidermis on the 7th day after culture. To the 20th day culture in vitro, the floral organ primordia were differentiated on the cut edge. On the 30th day culture, floral buds with petal, stamen primordia were observed. In addition, the morphological changes in the cultures of sepal segment were studied during the 14 to 30 days culture with scanning microscopy as well.

[Effect of gibberellin on direct regeneration of floral buds from young flower buds in Sinningia speciosa Hiern].

The phenomena of direct regeneration of floral buds on young flower bud and sepal cultures in vitro were observed in Sinningia speciosa Hiern. The gibberellin concentration in medium was very important for inducing the direct regeneration of floral buds. No direct floral bud was regenerated when the concentration of gibberellin (GA) supplemented in medium was equal to or less than 0.5 mg/L. The young floral buds and sepals inoculated on modified Murashige and Skoog (MS) medium supplemented with 1.0-1.5 mg/L GA and 0.1 mg/L 6-benzylaminopurine (BA) for 40 days produced floral buds directly on the surface of the sepals. There were two types of the floral buds regenerated directly: one was only with floral buds, which was up to 14.3%; the other was with both floral and vegetative buds, which was up to 28.6%. The effect of exogenous GA on the formation of floral buds in Sinningia cultured in vitro is discussed.

[Expression of CFL gene during differentiation of floral and vegetative buds in cucumber cotyledonary nodes cultured in vitro].

CFL gene, a LFY homologue, was cloned from cucumber (Cucumis sativus L.). In this paper, in situ hybridization was performed to analyze the expression pattern of CFL gene at the stage of floral and vegetative buds differentiation in cucumber cotyledonary nodes cultured in vitro. The results showed that at the stage of floral differentiation, CFL gene was strongly expressed in primordia, floral organ primordia, and each whirl of floral organs at the early stage of their formation, but weakly expressed or not expressed in floral organs after their formation (Fig. 2). At the stage of vegetative bud differentiation, CFL gene was strongly expressed in meristem, leaf primordium and young leaves, and no apparent expression signal was detected in mature tissues (Fig. 3). The results suggest that the expression of CFL gene be necessary for the differentiation and formation of floral and vegetative primordias, and it plays an important role in floral and vegetative development in cucumber. The results also indicate that CFL gene involving in mitosis initiation, mitosis controlling, and transformation of vegetative meristem to floral meristem.

[Regulation network and biological roles of LEAFY in Arabidopsis thaliana in floral development].

Recent research progress on regulation network and biological roles of LFY gene in Arabidopsis thaliana and its homologue genes in floral development are reviewed emphatically in the present paper. LFY gene expresses widely in both vegetative and reproductive tissues in different higher plants, therefore investigation on role of LFY gene on flowering is of general significance. LFY gene plays an important role to promote flower formation by interaction and coordination with other genes,such as TFL, EMF, AP1, AP2, CAL, FWA, FT, AP3, PI, AG, UFO, CO, LD, GA1 etc, and a critical level of LFY expression is essential. LFY gene not only controls flowering-time and floral transition,but also plays an important role in inflorescence and floral organ development. It was situated at the central site in gene network of flowering regulation,positively or negatively regulates the level or activities of flowering-related genes. Some physiological factors, such as carbon sources, phytohormones, affect directly or indirectly the expression and actions of LFY gene. This indicates that level of LFY expression can also be regulated with physiological methods. It is probable that we can explain the principal mechanism of flowering by regulation network of LFY gene.

[Floral homeotic variants of in vitro seedlings in Sinningia speciosa Hiern].

Six types of floral homeotic variants of in vitro seedlings were observed in doubleflower sinningia. Type I, red and green mosaic petals exist in the outermost whorl of petal-whorls, 2.38%. Type II, the outermost whorl of petal-whorls exhibit green petals with thin yellow edge, 25.0%. Type III, green petals exist in the innermost side of normal red petal whorls, 1.78%. Type IV, multiple whorls of green petals exist in the inner side of normal sepals, no stamen and carpel, 1.67%. Type V, it exhibits duplicated whorls of sepals in the outermost, 7.14%. Type VI, it exists multiple whorls of green sepals, no petal, stamen and carpel, 0.12%. The total percentage of all types of floral homeotic variants is up to 38.1%. The distribution of nodal site of homeotic flowers were analyzed, and the results showed that the homeotic flower occurred mainly at the fourth and fifth nodes.

[Relationship between floral differentiation and endogenous hormones and polyamines contents in cucumber cotyledonary nodes cultured in vitro].

Changes of endogenous hormones and polyamines(PAs) contents during floral differentiation (0-6 day) in cucumber cotyledonary nodes cultured in vitro were determined by using HPLC. The results showed that all four endogenous hormones decreased obviously within 0-2 day and increased slightly within 4-5 day after culture. This indicated that low levels of indole-3-acetic acid (IAA), gibberelline(GA3) and abscisin acid(ABA) during 0-2 day were favorable to floral primordia differentiation, while high level of zeatin(ZT) during 3-5 day was favorable to floral organ primordia differentiation. Contents of spermine(Spm), spermidine(Spd) and cadavarine(Cad) were decreased within 0-1 day, but increased within 1-4 day, and then decreased again within 4-5 day after culture. On the contrary, content of putrescine(Put) was increased significantly on the first day and then declined during 1-6 day. Changes of PAs contents indicated that high levels of PAs and Put were favorable to floral primordia differentiation, the increasing of Spm after the second day was favorable to floral organ primordia differentiation, and change of Cad content may be one of the characteristic symbols between floral and vegetative bud differentiation.

[Studies on calcium sensitive period during floral differentiation of cucumber cotyledonary node cultures in vitro].

Cotyledonary nodes of cucumber cultured on calcium-free medium for 0, 1, 2, 3, 4, 5, 6d respectively, were transferred to medium with 6.0 mmol/L CaCl2 for 24h, then returned to calcium-free medium. Cotyledonary nodes cultured on calcium-free or 6.0 mmol/L CaCl2 medium for all time, were taken as controls. Results showed that cotyledonary nodes were transferred to 6.0 mmol/L CaCl2 medium for 24h during 0-3d after the beginning of culture, percentage of floral bud formation at cotyledonary nodes was increased significantly. Transferring cotyledonary nodes on the 3d day after the beginning of culture was achieved best effect, percentage of floral bud formation was up to 34.3%. We deduced that the calcium sensitive period during floral differentiation of cucumber cotyleddonary node cultured in vitro may be 0-4d after the beginning of culture.